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Railway Bridges

Today and Tomorrow

22-23 November 2006

Marriott Hotel City Centre, Bristol

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Railway Bridges - Today and Tomorrow 3

Foreword

I am pleased to welcome you to the third in the series of successful Network Rail sponsored supplier 

conferences. This time the subject is "The Maintenance and Renewal of Bridges".

The majority of Network Rail's bridges are over 100 years old and are constructed in a variety of materials,

for example cast iron, wrought iron, steel, reinforced concrete, brick, masonry and timber. Future

construction is likely to use more complex forms of composite construction, in particular fibre reinforced

polymers which are already being used to strengthen bridges.

The age and variety of materials presents interesting challenges to Network Rail in order to maintain its

bridges in a safe and fit for purpose condition, as part of a safe, reliable and efficient railway. I believe that

there are opportunities within the Bridges Renewals and Maintenance Portfolios to achieve significant

savings through promoting best practice, adopting lessons learnt and innovative thinking. In addition,eliminating the need for lengthy line closures to do work is an essential part of tomorrow's railway.

Converting these opportunities into actual savings, whether financial or process time or avoidance of 

traffic interruption, forms an essential part of achieving the efficiency targets set by the Office of Rail

Regulation.

Selected key suppliers with experience in the design, construction and maintenance of bridges were

invited to submit technical paper synopses on a range of topics for presentation and debate at the

conference. The topics were very varied and included composite materials, safety, innovation and new

materials, minimum future management and maintenance costs, repair and strengthening versus

renewal, standard designs and details, grade separated junctions and direct track fastenings.

The findings from these papers will support the drive for greater efficiency and the delivery of whole life

cost structures. This document contains the fourteen papers which were selected for formal presentation.

The choice of papers was made jointly by representatives from the Engineering and Major Projects &

Investment functions of Network Rail. I extend my thanks to all of you who took the time and trouble to

submit a synopsis.

You are all key stakeholders and vital links in the supply chain which maintains and renews Network Rail's

bridge assets. I trust that you will continue to work with us to provide a safe, reliable and efficient railway.

Professor Andrew McNaughton

Chief Engineer

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Railway Bridges - Today and Tomorrow4

Contents

Paper Title

One Getting the most out of bridge renewals

Design is more than BS5400....Network Rail

Two Repair and Strengthening versus Renewal

Mott MacDonald

Three Jamestown Viaduct - Innovative Strengthening of an Early Steel Viaduct

Corus Railway Infrastructure Services

Four  Innovative Techniques Used in the Life Extension Works of Leven Viaduct

Carillion

Five Development o f Standard Designs and Details for Railway Bridges

Network Rail

Six Delivery of Works - Safely

 Alfred McAlpine Project Services

Seven Track/Bridge Interaction and Direct Track Fixing

Cass Hayward & Partners

Eight Soil/structure Interaction and Railway Bridge Structures

Ove Arup

Nine Innovation Now & in the Future

Fairfield-Mabey

Ten Design for Future Minimum Management/Maintenance Costs

Gifford

Eleven  Advances in Rail Underbridge Replacements

Hyder Consulting (UK)

Twelve Forth Bridge Safety and Production

Balfour Beatty Civil Engineering

Thirteen Skills Competency in the Painting Industry:

The Industrial Coatings Applicator Training Scheme

Institute of Corrosion

Fourteen Recent Developments in Strengthening Technology and the

Strengthening/Reconstruction Decision

Mouchel Parkman/Tony Gee and Partners JV

Page

7

17

23

31

39

47

61

65

75

81

87

97

103

107

Day One 5

Day Two 73

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Railway Bridges - Today and Tomorrow 5

Day One

22 November 2006

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Railway Bridges - Today and Tomorrow6

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Railway Bridges - Today and Tomorrow 7

Paper One

Getting the most out of bridge renewals

Design is more than BS5400....

Ian Bucknall

NETWORK RAIL

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 Abstract

The design and construction of railway bridges is one of 

the most rewarding jobs in the rail industry. We follow the

successes of engineers who built and maintained Network

Rail's most populous and longest lasting assets.

Design decisions made by today's engineers dictate

whether Network Rail gets the most out its investment inrenewing bridges in its 40,000+ bridge stock. The

purpose of this paper is to challenge those involved in

design decisions to reconsider some of the broader 

aspects of successful design.

We must use the opportunity presented by every renewal

to deliver reductions in the on-going management and

maintenance of the bridge stock. The paper examines

Network Rail's functional requirements that will assist with

ensuring designs deliver these objectives and other key

design requirements that have to be satisfied to ensure

long lasting bridges that will serve the railways for inexcess of 100 years.

The functional requirements for railway bridges cover 

normal operations and abnormal situations - both

unplanned and planned. Those familiar with the

requirements for road bridge design will see significant

additional requirements. The site specific constraints we

inherit from the initial construction of the railways,

especially limited construction depth - together with our 

need to carry out the renewal with minimum disruption to

rail traffic - frequently dictate practicable structural forms.

The paper concentrates on the renewal of underlinebridges, recognising that many of the issues raised are

equally applicable to the renewal of overline bridges and

footbridges.

Optimising design to deliver Network Rail's requirements

at least initial cost maximises the benefits of Network

Rail's investment. Putting the benefits of the investment

at risk from insignificant reductions in initial cost would not

be a success for the rail industry.

1. Introduction

With 40,000+ bridges Network Rail seeks to maximise the

benefits of every bridge renewal. Typically bridge

renewals are carried out to:

• address shortfalls in bridge capability to carry required

railway loads

• address significant condition issues

when consideration of:

• optimal whole life structure maintenance costs

• the need to minimise the risk of temporary speed

restrictions, and;

• other risks that could potentially lead to delays to train

services or restrictions on operations

indicate replacement is the preferred option.

The design decisions made on individual bridge renewals

contribute to Network Rail's overall business objectives -

to improve the reliability of the railways and reduce the

funding requirements for the on-going management andmaintenance of the infrastructure to affordable levels. To

support these overall business objectives, good design:

• delivers the client's functional requirements

• ensures that the proposed works are capable of 

execution with minimal disruption to the client's

operations - and especially the client's customers (in this

case the ultimate users of the railways)

• minimises whole life costs by achieving the appropriate

balance between initial costs and the client's on-goingmanagement and maintenance costs

• realises the benefits of innovative techniques whilst

ensuring the risks associated with such innovation are

acceptable

• ensures that the proposed works will be as successful

as the designs of previous railway engineers, who built

and maintained bridges that have given good service for 

approaching 150 years

This paper concentrates on the first and last of the above,

and aligns with Network Rail's policy of leading the

decision making on its infrastructure and acting as an

expert client in directing bridge renewal activity. Issues

such as discharge of CDM responsibilities, sustainability

and minimising the risk of possession overruns etc., are

outside the scope of this paper.

2. Functional requirements for underline

bridges

The functional requirements for underline bridges may be

categorised as:

• requirements for minimising structures management

and maintenance - easy to manage and durable

• requirements for normal operation

• requirements for satisfactory performance during

abnormal operation - both unplanned and planned

situations

2.1 Easy to manage and durable

With 40,000 bridges to maintain it is essential that everyopportunity presented by a bridge renewal for reducing structures

management and maintenance costs is taken. To facilitate this

objective the design should address the following requirements.

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2.1.1 Water management

To maximise the life of the structure it is essential to

consider at the start of the design how water will be

managed.

Positive falls, camber, good detailing practice such as

provision of drips and weather flats, avoidance of debris

traps etc. should all be included in the design.

It should be assumed in the design that waterproofing will

fail in the life of the structure. Positive water management

will maximise the life of the structure whilst the benefits of 

repairing the waterproofing are evaluated (the cost/

disruption of gaining access by removing the track to most

rail bridges is high).

2.1.2 Durability requirements

In addition to the requirements in the industry standards

sufficient durability will be achieved by:

• appropriate selection of materials• appropriate workmanship specifications

• protective treatment in accordance with Network Rail's

performance specification

Further details are outside the scope of this paper.

2.1.3 No debris traps

Experience with existing bridges indicates that debris

trapped in elements promotes greater rates of corrosion of 

metallic elements / deterioration of protective coatings. To

maximise the life of the structure the structural form and

detailing should minimise potential debris traps.

2.1.4 Structural behaviour easily understood

Unnecessary structural complexity and less common

structural forms greatly increase the management and

maintenance costs of railway bridges. In design the

designer has the luxury of many weeks or months to gain

a full understanding of behaviour. When faced with the

task of evaluating "bridge bash" damage and the need to

restore railway traffic in hours such complex structures

are unacceptable.

Network Rail already owns a significant number of historic

landmark structures that require significant managementresources. Any additional proposals for further landmark

structures will only be supported where there is a

compelling business requirement, and such requirements

will be specified by Network Rail.

2.1.5 Fai lure modes

In the unlikely event of the structure being at risk of a

structural failure the design of the structure should be

designed, such that:

• the critical failure mode is one which gives warning

signs of the impending failure (e.g. fail in bendingbefore direct tension failures)

• consideration should be given to providing alternative

load paths [e.g. shear flats (or other physical means) in

cross girder to main girder connections, so that in the

event of bolt failure the deck does not drop with the

potential resultant effect on track alignment

disproportionate to the structural failure]

Structures should not require any special examination

requirements. Preferably, signs of distress should be

capable of being detected by the normal annual visual

examination process.

2.1.6 No hidden detai ls

 All main structural elements should be visible from at last

one side.

If this is not possible advice should be sought from

Network Rail at an early stage in the design and

consideration given to providing alternative load paths

that ensure the structure is still acceptable w.r.t the

ultimate limit state and w.r.t. traffic safety deformation

requirements (e.g. former practices of installing

longitudinally post tensioned beams with anchoragesburied under the tracks, preventing access to critical

components, is no longer acceptable).

2.1.7 Access to structural elements

 All elements of the structure should be accessible for 

examination and maintenance.

2.1.8 Robustness

It is desirable for elements of the structure to have a

degree of robustness so that they are not damaged by

unforeseen events disproportionate to the cause. For 

example:

• main girders in half through bridges designed to span

between abutments without the assistance of tension in

the floor (and the main girder / floor connection

checked for adverse longitudinal shear flows and the

floor designed to resist global tension effects)

• bearing stiffeners on main girders formed from two

plates rather than one are more tolerant of eccentricity

of bearing reaction resulting from substructure

movement

• stiffeners to box girder diaphragms formed from plateswith low outstand ratios that can accommodate

excessive load by yielding instead of buckling (also see

Failure modes above and Resistance to bridge bash

below).

2.1.9 Substructure movements

Replacement bridge decks should be designed to

accommodate differential settlement and on-going

movement of existing abutments etc.. Where

longitudinally free bearings are provided at one end of the

deck, consideration should be given to fitting "long stops"

to free movement to facilitate the deck acting as a strut, toresist excessive abutment movement.

Special considerations apply in areas of mining

subsidence.

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Note: It is generally acceptable to reuse existing

abutments when replacing the superstructure providing

the substructure is subject to a similar pattern of loading.

See GC/RC5110.

2.1.10 Deter pigeons

To minimise future maintenance and inspection costs the

design should incorporate provision to deter pigeons.

2.2 Normal operations

The requirements for normal operations are:

2.2.1 Capability to support load

Rail bridges must have adequate strength to carry railway

traffic and other variable/permanent loads for the

anticipated volume of traffic, in accordance with the

requirements of the relevant standards including BD37 and

BS5400 etc..

The standard design load models - RU in BD37 or LM71 inEN1991-2 (together with the additional load model SW/0

for checking continuous structures) - in conjunction with

the associated dynamic factors cover normal rail traffic

loads. The load models include a margin in comparison

with assessment loading requirements, that permits

flexibility in the timing for strengthening works for 

structures that have with time deteriorated and no longer 

meet design requirements but still meet assessment

requirements.

For bridges designed for speeds in excess of 125mph - or 

for "lightweight metallic decks" for speeds over 100mph -

additional checks are required to ensure that the design

caters for the greater of:

• conventional loading, or 

• the load effects determined from a dynamic analysis of 

the structure subjected to the new European high speed

load model HSLM in EN1991-2.

Extensive studies of the dynamic behaviour of the modern

standard Network Rail box girder bridge indicate this form

o construction is satisfactory for speeds up to 125mph.

In the future, on lines where the Technical Specifications

for Interoperability apply, the TSI requirements for design

and the minimum standard for infrastructure are the same.

In the UK we will be designing new bridges for an

additional margin of 10% at ULS to ensure that we

continue to benefit from the current flexibility to decide the

timing of strengthening works.

The design should allow for the required number and

position of tracks including allowance for tolerance in their 

position. The standard safety factors provide an allowance

for increased ballast loading due to future track lifts.

Finally, our guidance on specifying fatigue loading

requirements provides allowance for future growth in

traffic.

2.2.2 Acceptable deformation

In comparison with road bridges, bridges supporting rail

traffic are subject to more onerous deformation limits to

ensure the safety and comfort of rail traffic and

passengers, and limit the effects of deformation on the

track. Deformation limits are specified in railway industry

standards including UIC leaflets and in the future will be

superseded by the bridge performance criteria specified in

EN1990 Annex A2.

Excessive bridge deformations can endanger traffic by

creating unacceptable changes in vertical and horizontal

track geometry, and excessive rail stresses & vibrations in

bridge structures. Excessive deformations can also affect

the loads imposed on the track/bridge system, and create

conditions which cause passenger discomfort.

Generally, deformations are calculated using nominal

loads. The live load to be taken into account includes

vertical loading enhanced by dynamic factors, centrifugal,

nosing and traction, and braking. For ballasted decks,effects such as creep and settlement of foundations may

be assumed to be addressed by track maintenance.

Midspan vertical deflection of the bridge under dead and

superimposed dead loads is checked to ensure that the

natural frequency of the structure is within the known

limits of validity of the allowances for dynamic load effects

in the dynamic factors used in design.

Track twist under load occurs when, for a cross section

normal to the track at any given position, the deflection of 

the structure under one rail is different from that of the

other rail. Excessive track twist can cause a derailment.

Track twist should be considered for all locations from off 

the bridge (no twist) through the transition region onto the

bridge, across the bridge, and through the transition

region off the bridge. Twist is checked along the

centreline of each track over a gauge length of 3m parallel

to the tracks taking into account the worst possible

combination of tracks loaded and position of rail loading.

Track twist should always be checked on skew bridges. It

can also occur to a lesser extent on bridges subject to

eccentric live load, e.g. double track bridges with onetrack loaded.

When comparing track twist with the values permitted in

UIC Leaflet 776-3R the total track twist should be

considered. The total track twist includes any intended

track design twist resulting from the intended rate of 

change of cant that may be present in a transition curve in

the track.

Twist effects are likely to be particularly severe for highly

skewed bridges where track twist limitations frequently

govern the overall design of the bridge. Track twist inregions of skewed intermediate supports in a series of 

simply supported spans can be particularly critical.

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Unrestrained uplift at any bearing is not permitted to avoid

the resultant vertical displacement of the track and to

avoid premature failure of the bearing. Uplift should be

checked for bearings at the acute corners of skewed

bridges and at the ends of continuous structures.

Uplift at the end of a deck occurs where the deck beneath

the track extends (away from the span) beyond the

bearings. The vertical downward deflection within thespan is matched by a corresponding upward deflection of 

the deck beyond the bearing.

Uplift is limited to avoid destabilising the ballast and limit

uplift forces on track components and ensure acceptable

additional stresses in the rails. Current thinking is that the

limits in UIC 776-3R are not adequate. To maintain

acceptable track quality, recent European research

indicates that the uplift should not exceed about 2mm and

this limit (also in EN1991-2) is likely to be included in a

future Network Rail standard on the design of bridges.

Vertical deflection at midspan under rail loading is

checked to ensure acceptable vertical track radii, that the

structure is not significantly different in performance to

existing rail bridges, and to ensure acceptable levels of 

vertical acceleration inside coaches corresponding to

satisfactory passenger comfort.

To simplify bridge design and avoid the need for 

train/bridge dynamic interaction, analyses permitted

span/deflection ratios as a function of structural

configuration, span length, speed and passenger comfort

are currently given in GC/RC5510 and UIC Leaflet 776-

3R. These requirements are likely to be superseded by

the advice in EN1990 Annex A2.

In addition, with the maximum adverse rail loading pattern

the maximum vertical deflection should also not exceed

L/600 (EN1990 Annex A2).

For requirements relating to the twist effects of vertical

deformation - which can dictate design - see the above

section on Track twist.

Longitudinal load effects generated in the track by vertical

deflection of the deck etc. Vertical deflection in the spancause a rotation about a transverse axis at the end of the

deck and, depending upon the height of the upper surface

of the deck above, the bearing a corresponding

longitudinal displacement. Together with longitudinal

displacement of the substructure, traction and braking

loads and temperature contraction and expansion these

actions develop additional stresses in the rails and

additional forces on the bearings.

This combined response of the bridge to variable actions

is called track/bridge interaction and can dictate the

design of longer span bridges, multiple spans or continuous bridges. Where track/bridge interaction

checks are required to be carried out by GC/RC5510,

EN1991-2 6.5.4 should be assumed to supersede the

advice in UIC Leaflet 774-3R (also see below).

Rotation of the ends of the deck about a transverse axis

under rail loading: Checks are made on the rotation of the

end of the deck or between the ends of adjacent deck to

limit uplift forces on track components and ensure

acceptable additional stresses in the rails, and limit

angular discontinuities in rail expansion devices and at

switches.

EN1991-2 specifies the relevant requirements. Wheretrack/bridge interaction effects are required to be taken

into account the associated checks on limiting additional

rail stresses may be critical.

For decks with non ballasted track the effect of rotation of 

the end of the deck and any uplift at the end of the deck

should be taken into account when determining the load

effects on the rail fastenings, and compared with the

relevant limit state (including fatigue) performance

characteristics of the rail supports and fastening system.

Longitudinal displacement of the end of the deck: Wheretrack/bridge interaction effects are to be taken into

account then the limits in EN1991-2 section 6.5.4 on

longitudinal (and vertical) displacement of the ends of a

deck should be satisfied.

Lateral deformation of the deck under variable loads should

not exceed the maximum values given in UIC Leaflet 776-3R

to ensure acceptable track geometry and passenger comfort.

The limits are defined in terms of the maximum permitted

change in track radius and the maximum change of angle at

the end of a deck. The maximum change of angle is about a

vertical axis and should be assumed to apply to both ends of 

a deck and to the maximum total change of angle between

adjacent decks.

To avoid the occurrence of resonance between the lateral

motion of vehicles on their suspension and the bridge:

• the lateral flexibility of the bridge should not exceed the

limit in GC/RC5510 clause 19.8.4

• the lateral frequency under permanent loads should not be

less than the limit in GC/RC5510 clause 19.8.4

The above limits are not likely to be critical for short to mediumspan bridges with solid decks and high in-plane shear stiffness.

Vertical acceleration of the deck: For bridges designed for 

speeds in excess of 125mph or for "lightweight metallic decks"

for speeds over 100mph, additional checks are required to

ensure that the bridge deck will not be subject to excessive

dynamic effects including resonance. In such cases,

additional vibrations limits relating to the magnitude of deck

acceleration are required to guard against the risk of ballast

instability. The design of these bridges is outside the scope of 

this paper and further advice should be sought from Network

Rail (as indicated above, studies of the dynamic behaviour of the modern standard Network Rail box girder bridge indicate

this form of construction is satisfactory for speeds up to

125mph).

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Effect of deformation on clearances and drainage: When

checking clearances and designing drainage, allowance

should be made for deflection of the structure, e.g. the

relative deflection between the track supported by a

bridge and an adjacent platform carried on a structure

independent of the bridge can govern the design of a

bridge for medium to long spans.

2.2.3 Structure Gauge requirementsIn the design of many railway bridges the space permitted

by the structure gauge for fixed infrastructure is utilised to

its maximum extent.

The shape of the structure gauge, along with the available

construction depth and any width constraints arising from

reusing existing abutments and restrictions on

construction methodology determines the potentially

feasible structural forms at a site.

Depending on bridge span and deck width, half through

forms of bridge construction use the depth from soffit totop of main girders:

• up to top of rail level for the narrowest decks

(shallowest floor structural depth)

• up to platform level for medium spans with the resultant

longer transverse spanning floor members requiring

slightly greater construction depth

• where the above height provides insufficient depth for 

adequate main girders, the width (and hence depth) of 

the floor is increased to enable the main girders to be

placed outside the "structure gauge"

Details of structure gauge requirements are contained in

the relevant railway standards.

2.2.4 Safe working environment

The design of the bridge should minimise risk to people on

or about the bridge - whether they are:

• staff working on the structure

• other infrastructure maintenance staff, or 

• unauthorised persons

Care should be taken to meet statutory requirements for 

safe working areas at height with the design providing

adequate handrailing etc.. Kickers should be provided to

walkways and also detailed to minimise the risk of items

on the walkway falling onto persons below the structure.

Similarly narrow gaps between elements at track level

should be infilled to minimise the risk of ballast falling on

persons below. Minimum bolt sizes and plate thicknesses

should be selected to ensure these elements meet the

requirements taking into account the likely section loss in

the life of the structure.

The relevant standard should be consulted for the

requirements relating to the provision of walkways and/or 

continuous positions of safety across the structure.

Handrailing on the tops of abutments between adjacent

decks should be provided with mesh infill to retain debris

caught by the passing slipstream of trains. Generally, new

brick walls should not be provided in these locations to

minimise the risk of brickwork hitting persons below in the

unlikely event of the wall being hit by a derailed train.

2.2.5 Accommodate requirements of other 

discipl ines including operational requirementsThe structural form and detailing of the bridge should be

designed to ensure a satisfactory interface with other 

railway disciplines including:

• accommodating the track curvature, cant and position

• accommodating future track slues and lifts (in addition

to the design accommodating generous tolerances in

the as constructed position of the deck

• accommodating common and site specific track

configurations and component details

• ensuring no adverse effect on signal sighting

(especially ground signals)

• ensuring no adverse effect on sight lines for train

dispatch staff 

• minimising the risk of trespass and vandalism at the

site

• accommodating specific infrastructure specified by

Network Rail such as signals, point machines, location

cases for signalling equipment etc.

• including provision for cable routes for signalling

telecommunication, electrical control and electrical

power cables across the bridge

• accommodating track drainage requirements

It is recommended that the design of the "corners" of the

bridge be undertaken at an early stage as it can affect the

final size and configuration of the superstructure. Care is

needed to ensure that requirements relating to the site

constraints relating to structure gauge, bearing positions,ballast wall arrangements, size of existing abutment tops,

adjacent infrastructure, access to bearings, walkways on

and off the bridge, cable route requirements, ballast

retention etc. are met.

2.2.6 Aesthet ics

The appearance of the bridge should reflect the importance

Network Rail places on its investment in infrastructure.

Generally the structure should be sympathetic to its

surroundings. A number of the essential requirements for 

the safety of the structure tend to dictate structural forms

and member sizes which tend to give railway bridges adistinctive appearance. Honesty in structural form should be

respected and care taken with structural details, to provide a

visual demonstration of Network Rail's commitment to

maintaining and enhancing the nation's railways.

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 Any planning applications or consultation with planning

authorities should always be through Network Rail to

ensure the project enjoys Network Rail's planning rights.

 Additional requirements apply to the renewal of listed

structures or structures in conservation areas and in such

cases advice should be sought from Network Rail on the

particular requirements for the project.

2.3 Abnormal si tuat ions (unplanned)

In addition to performing satisfactorily under normal

operations bridges are expected to meet their required

functions/not suffer damage disproportionate to the cause

of the accidental situation.

2.3.1 Resistance to "bridge bash"

Coincident with the renewal of an underline bridge the

opportunity should be taken to ensure that the resultant

structure can continue to carry rail traffic in the event of a

"bridge bash" at the site.

In addition to the requirements in Network Rail's

standards, the designer should also consider the following

strategies:

 Avoid

is it reasonably practical to provide an increase in

headroom to 5.7m to make bridge strikes unlikely?

Protect

provision of a protection beam (these should not

carry critical functions such as signalling cables)

Mitigate

restrain the bridge from moving sideways / restrain

uplift

add mass to the structure

provide a flat soffit or ensure floor can adequately

carry loads at ULS if one member removed

Robustness

provide stocky flanges

stiffen web

provide additional main girder flange thickness to

compensate for damage / facilitate repair options

(e.g. dressing of gouges in steel)

Design

deck for industry accidental loads

2.3.2 Resistance to derailment

For the much less likely and more extreme situation

relating to the derailment on a bridge the bridge isexpected to withstand the accidental scenario of a

displaced train without collapsing or overturn (En1991-2

and BD37). For such scenarios local damage is tolerated.

Good bridge design also considers the following

strategies:

Protect

the end of main structural girders

intermediate stiffeners by placing them on the outer 

side of main girders (if provided to a centre girder the

bridge should be adequate without the stiffeners onone side of the girder)

robustness in main girders

provide internal robust kerbs to protect discrete

elements such as truss members above track level

Mitigate

robust kerbs are provided to retain the train on the

bridge

accommodate the standard rail loading in adisplaced position corresponding to the retained train

the bridge should not overturn and "make the

derailment worse"

single bearing stiffeners should be avoided in the

vicinity of the tracks so in the event of one being

crippled "all capacity is not lost"

Design

for industry loads

Bridge decks are also designed to resist a point load of 

250kN to ensure they have adequate robustness and to

cater for jacking forces generated by rerailing equipment.

The above requirements generally preclude open mesh

infill to grillage floors

2.3.3 Other unforeseen accidental scenarios

Other unforeseen accidental scenarios are mitigated by

general robustness.

For particular issues such as ship impact the relevant

industry standards should be met.

2.4 Abnormal s ituat ions (p lanned)

2.4.1 Track maintenance and renewal

Sufficient ballast depth, typically 200mm, should be

provided to minimise the risk of tamper tynes damaging

waterproofing/the deck (generally a greater ballast depth

will be required to satisfy track construction standards).

Decks with more than one track should be designed to

allow for any adverse effects from the removal of track

and ballast on one deck.

13Railway Bridges - Today and Tomorrow

Paper 1 Getting the most out of bridge renewals

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Designers should consult Network Rail on the

requirements for accommodating track renewal plant on

decks on single track lines (e.g. for accommodating single

line track relaying gantries).

Checks should be carried out to ensure new decks can

accommodate the loading from the latest generation of 

railway cranes (e.g. KIROW cranes).

2.4.2 Allowance for excessive dynamic wheel / rail

forces on unballasted decks

Unballasted decks without longitudinal timbers should be

designed for a ULS design load of 600kN point force (with

no additional increment required for dynamic effects) at a

single/along any one rail support to allow for the dynamic

forces generated by out of round wheels / wheel flats

(generally mitigated by the mass of conventional track

components).

2.4.3 Replacement of bridge parts

Provision should be made for the replacement of partswith a design life less than that of the structure. In

particular provision should be made for jacking the

structure to replace discrete bearings.

2.5 Instal lat ion / demol it ion

Typical constraints that influence feasible structural forms

and details include:

• the need to execute bridge renewals with minimal

disruption to users of the railway (dictates the design of 

nearly all railway bridges)

• availability of railway possessions to undertake the

installation of the replacement deck

• health and safety considerations dictating acceptable

construction techniques

• the presence of overhead line equipment and

temporary arrangements such as cable bridges for 

maintaining railway services throughout the works

• site access and limited site space constraints (e.g.

inner city sites generally require the majority of works tobe carried out off site and site works limited to primarily

installation of whole decks or in-situ installation of 

prefabricated units)

• the proximity of adjacent structures and property

owned by Network Rail's neighbours

• generous allowances for construction tolerances,

particularly where component tolerances are cumulative

In addition the risk of possession overruns that disrupt rail

services must be avoided.

Recent advances in bridge construction techniques

utilising the latest generation of high capacity cranes and

transporter systems enable the maximum amount of 

works to be competed in advance of the main possession

to install the replacement deck. This tends to reduce

possession overrun risks and enables the structure to

benefit from higher standards of workmanship.

Further discussion of these issues is outside the scope of 

this paper and other papers at the conference will expand

on these issues.

3. Conclusions

Network Rail seeks support from all those who influence

the design of bridge renewals to rise to the challenge of 

maximising the benefits from our increasing investment in

infrastructure.

The decisions made during design have a major influence

on the suitability of the structure to meet the needs of the

railway’s customers and stakeholders. If we are to

perpetuate the success of the engineers that built and

maintained the railway before us we must ensure that allwork on our bridge stock satisfies the necessary

functional requirements.

This paper supports Network Rail's policy of leading such

works as an expert client in partnership with our suppliers

and identifies the key requirements expected of bridges:

• easy to manage structures with minimal maintenance

costs, no hidden details and the robustness to deliver 

reliable rail services under normal and abnormal

conditions

• to carry the required loadings with acceptable

deformation

• with structural forms that satisfy structure gauge and

site specific geometric constraints

•bridge that can be safely constructed and maintained

with minimal disruption to the railway’s customers.

With bridges having an expected life of well over 100

years, it is essential for designers to address the key

business demand for ease of management and reduced

maintenance costs in support of the company's drive toensure railways are more affordable. Designers need to

rise to the challenge of ensuring that the many 100s of 

"ordinary" bridges that we replace deliver the performance

and reliability expected of today's railway, and that they

can be built and maintained with minimal adverse impact

on railway customers.

Network Rail places significant demands upon its bridge

stock, and by ensuring that the design of replacement

bridges meets both normal and abnormal operational

needs with margins for growth in traffic, they should serve

us well into the future - thus making the most of theopportunities that arise from bridge renewals.

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4. References

Network Rail Company Standard NR/SP/CIV/020 "Design

of Bridges & Culverts" (Draft)

SCI, "The Design of Steel Railway Bridges", SCI, Ascot

I Bucknall, "Atlantic Road Bridge Brixton", Structural Steel

Design Awards, BCSA, London, 1991

I Bucknall, "New Eurocode requirements for the design of 

high speed railway bridges", IABSE Conference, Antwerp

2003,

Various unpublished Eurocode Project Team documents

supporting the development of railway loading and rail

bridge performance requirements in EN1991-2 and

EN1990 Annex A2.

ERRI Committee D214/RP9 Rail bridges for speeds >

200km/h. Final report, Part A Synthesis of the results of D214 Research, ERRI, Utrecht, 1999

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16 Railway Bridges - Today and Tomorrow

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17Railway Bridges - Today and Tomorrow

Paper Two

Repair and Strengthening versus Renewal

Matthew Kynoch

MOTT MacDONALD

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Introduction

To determine the investment for an existing metallic bridge

asset, a logical process must be adopted with significant

business / strategic and technical milestone appraisals in

order to provide a cost effective means of safeguarding

the integrity of the operational railway.

The majority of metallic rail bridges were constructedbefore 1914 and many have already exceeded the

notional design life of 120 years as stipulated by modern

design standards.

The bridge stock has to be appropriately managed as they

all require regular inspections, assessments and routine

maintenance to verify their performance and structural

integrity. However, in general terms the bridge stock, as a

whole, has performed well exhibiting common conditional

and strength problems despite increased traffic loadings

and intensities. It is therefore inevitable that some will

require repair and strengthening or even completesuperstructure renewal.

This paper will aim to identify potential efficiencies by:

• Identifying the key evaluation criteria for comparing

life cycle costing between strengthening and renewal

schemes, including design and implementation best

practices which may influence the decision as to

whether to strengthen or renew

• Addressing theoretical shortfalls in a generic manner 

by the identification of common problems and commonsolutions be that through changes to standards or 

generic strengthening/repair details

When considering repair and strengthen versus renewal

of a particular bridge, the following key structure related

issues are of importance to the bridge owner:

• Safety of the structure and those that may be affected

by the structure

• Condition of the structure

• Load capacity of the structure in terms of strength and

fatigue/residual life

• Robustness/structural redundancy and resistance

against impact

• Provision of adequate clearances (gauge) between the

structure and the traffic on and beneath the bridge

Bridge Assessment

Before embarking on repair, strengthening or renewal it is

important to maximise both the assessment and condition

appraisal to determine the structure's safe load capacity

and life expectancy. To achieve this to the full, the

assessment codes must be challenged and all available

analyses/assessment techniques exhausted with

sufficient site inspections, intrusive investigations

undertaken to make an informed view on the residual life

of the structure.

Other factors that may be considered are increased

material strengths and operational restraints such as

speed and/or load restrictions. There are other appraisal

techniques available to validate assessment, such as Non

Destructive Testing, structure monitoring and load testing.

If the final assessment identifies a residual shortfall in

capacity, then increased capacity may be achieved in a

number of ways, for example by: 'Strengthening' including

modifying the infrastructure whole structure actions

(adding additional load distributing members); changing

local load paths (by the provision of additional primary /secondary members), or by local strengthening of 

individual elements/components or by Renewal.

Feasibility studies are commissioned for structures where

there are obvious advantages and disadvantages for 

repair/strengthening and renewal. The information

contained in these reports will form the basis of the

decision whether to repair and strengthen or renew.

Common Problems

Theoretical assessment failures generally fall into

common categories and considering that there are very

few known bridge failures various studies are on going to

challenge the code to see what conservatism, if any,

exists between theoretical shortfalls and actual behaviour.

Common strength problems with theoretical failures are

as follows:

• Centre main girder web shear 

• Flexure governed by lateral torsional buckling /

effective length/'U' frame action

• Rivet capacity (shear/bearing)

• Bearing stiffeners

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Paper 2Repair and Strength ening versus Renewal

Railway Bridges - Today and Tomorrow

Figure 1 - Concrete deck replacement

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Common condition related problems:

• Corrosion to trackside faces of webs/stiffeners located

 just above ballast/deck plate level (splash zone)

• Deterioration of girder ends/bearing plates where water 

runs off the ends of the deck

• Corrosion of metalwork through poor management of water through trough floors and deck plates

• Corrosion of supporting members directly beneath

wheel timbers

Repair and Strengthening

Traditional strengthening techniques involve the

installation of piecemeal steel plates connected byfasteners / welds so that they act integral with existing

structural components to resist a proportion of the live

load effect, noting that it is usually assumed that

permanent load effects are locked into the existing

structure unless otherwise alleviated during the

strengthening works.

One of the common problems following the assessment is

the theoretical shortfall in centre main girder end shear. It

is known that the assessment code has been updated and

is currently being further examined to see if any changes

can be made to enhance capacities to reduce potentialtheoretical failures. A 'top hat' generic repair solution has

been widely used to overcome this problem but has it

limitations as the top hat has to fit outside the existing

lower sector structure gauge clearances but nonetheless

is a very effective solution to improve structure capacity at

a relatively low cost.

Over recent years there has been a gradual introduction

in the use of Fibre Reinforced Polymers (FRP) or steel

plates bonded to the substrate to strengthen existingNetwork Rail structures. FRP have good fatigue and

corrosive resistance and are quick to install, non evasive

and benefits can be realised where welding or bolting is

not permitted, for example, when strengthening of cast

iron.

In knowing the common problems with metallic structures

through a maturing assessment programme, better 

grouping and generic repairs can be formulated - a

generic top hat solution being a good example.

Renewal

The available construction depth, lateral clearances and

track positions will to a large extent dictate the deck

replacement option. The majority of existing structures

and subsequent deck replacements tend to be of a half 

through type nature with a relatively shallow floor, limiting

the choice of replacement. Direct fastened track forms,

such as 'Edilon' where construction depth is restricted,

have been used but are not generally preferred due to the

maintenance management issues associated with them,

i.e lack of flexibility for track adjustment/tamping

operations.

Standard Design Details have been produced for a

number of bridge types, the principles of which are widely

used and referred to when considering deck

replacements.

Evaluation Criteria

When evaluating repair and strengthening versus

renewal, there are a number of key factors that need to be

considered on a bridge specific basis in order to arrive at

not only the most cost effective solution but the correct

solution for the particular asset in question.

The Four key evaluating criteria are as follows:

• Residual/Design Life

• Availability of funds

• Disruption (possessions/road/river closures)

• Site specific constraints (access/railway infrastructure

/third parties)

Residual/Design Life

The debate on design life will remain as to what lifeexpectancy can be reasonably realised through repair and

strengthening of a 120 year old asset, but provided that

the structure is not showing signs of distress or fatigue

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Paper 2 Repair and Strengthening versus Renewal

Railway Bridges - Today and Tomorrow

Figure 2 - Typical Girder Web corrosion

Figure 3 - Typical Top Hat Solut ion

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damage, it is reasonable to suggest, through regular 

future maintenance - post strengthening - that the

structure can sustain another 120 years in service.

However, most repair and strengthening schemes tend to

have a design life in the region of 30 to 50 years

associated with them.

It is also essential to recognise when a bridge is 'life

expired' or the risk of latent defects is unmanageable anda replacement solution is more appropriate than repair or 

strengthening. To make the decision whether to

strengthen or renew, it will also be necessary to take into

account the economic benefits the existing structure

brings to the Network, and the structure's

environment/aesthetics as well as its value to the

community.

 Availabi li ty of funds

Key determining factors can be evaluated when

comparing the merits for and against repair andstrengthening versus renewal for a single span or small

spanning multiple span structures. However for large

structures renewal is likely to be prohibitive, due to its vast

size, location/difficult access, environment and terrain it

spans over, and often repair and strengthening is the only

option considered.

For instance, there are very few examples of large remote

structures spanning over water that have been replaced

and those that have are usually as a result of concernsraised by sudden changes in perceived capacity or other 

strategic reasons.

These structures require major advance planning/funding

and for the purposes of this paper and the criteria for 

evaluating repair and strengthening versus renewal, only

single span or small multiple span structures will be

appraised.

There is an obvious funding difference between repair and

strengthening schemes versus complete superstructure

renewal schemes. Depending on size and complexity, theexpenditure for a typical replacement scheme is likely to

be in the region of £500k to £1M, whereas repair and

strengthening schemes the initial outlay is nearer £150k to

£500k. This combined with future maintenance and other 

costs to determine projected whole life costs has to be a

major contributory factor when considering which route to

take.

The status of the bridge is a key factor in firstly prioritising

work on the network whereby primary routes are often

looked upon differently to other routes. For example a

structure on a mainline which has cost benefits instrengthening over reconstructed may be renewed for the

very fact that it has an undesirable track form (wheel

timbers) and can easily be replaced with a concrete (low

maintenance) deck.

Where a marginal cost advantage is to be gained through

repair and strengthening as opposed to renewal, or 

whereby the strengthening is of a complex nature, or if 

significant hidden parts exist which could warrant

subsequent repair, it may be prudent to reconstruct.

Where track lifting or road lowering is considered

necessary to achieve the desired construction depth, thiscan often angle back in the favour of repair and

strengthening, but nonetheless be considered during the

feasibility stage.

 Advantage can be taken of carrying out more than one

repair and strengthening/replacement scheme on the

same line within the same possession, effectively

combining possession related incurred costs (tamping

machine/Permanent way resource etc.) and also

efficiencies can be realised in combining compound

facilities, resources. However, careful consideration

should be given to combining too many schemes at the

same time as the specialist expertise and competency

required in this field is limited.

The extent of the scope of repair and strengthening can

often result in a structure being reconstructed due to the

amount of disruption or rail possessions a repair and

strengthening scheme would require.

Disruption (possessions/road/river c losures)

The implementation cost is not necessarily directly linked

to the requirement to minimise disruption but the need for 

possessions/road/river closures is likely to dictate theconstruction programme and the resource required to

complete the works in order to meet that programme.

In general terms repair and strengthening schemes are

considered to be less disruptive to rail/road/river 

commuters whereby the work is typically carried out in

rules of route or shorter abnormal possessions. Compare

that to replacement schemes where 52 hours weekend

possessions are generally taken to remove the existing

and install the new bridge deck.

However, the public (non-rail users) may perceivestrengthening to be more disruptive as the programme

tends to be prolonged to suit preparatory work, piecemeal

erection and rail possessions and often underline bridges

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Paper 2Repair and Strength ening versus Renewal

Railway Bridges - Today and Tomorrow

Figure 4 - Hamble Viaduct Strengthening

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will require partial/full road closures for a period of weeks

to enable refurbishment/painting works to the soffit to be

undertaken. However, the public's appreciation of the

effort taken to avoid the need for disrupting trains often

goes unrewarded.

Noise generated by the works is not often looked upon as

a criteria for determining whether the structure is renewed

or strengthened but could have an influence on how thework is to be undertaken. Bridge sites located within built

up areas where significant rivet removal is required

usually receives its fair share of complaints as it is more

often confined to night times when trains are not running ,

and dependant upon the scope of rivet removal, can take

several weeks to remove. Often mitigation measures are

put in place to dampen the sound but from the public's

perception can be seen as disruptive or an inconvenience.

Whereas a bridge reconstruction is relatively intrusive at

the time but the duration over which it occurs is relatively

short and usually well publicised in advance.

The number and duration of trackside possessions for 

repair and strengthening schemes can sometimes be

dictated by the need for trackside painting works, many of 

which contain original lead pigment. Depending upon the

complexity of the structure and the ease in which

protection boarding/screening can be erected - to protect

not only the trains but against contamination of the

adjacent surroundings - the erection and dismantle time

can absorb a large number of possessions.

If there is insufficient space available to effectively screen

the operational railway from painting activities (such as

centre girders), significant possessions are required to

allow for encapsulation, blasting and reapplication of 

protective treatment. As a compromise mechanical

cleaning and single coat paint systems are often adopted

to reduce the number of possessions and complexity of 

the encapsulation system.

In some instances it may be more beneficial to remove the

painting from the strengthening contract and combine a

number of painting schemes on the same line to minimisethe overall disruption.

Design remits regularly state that strengthening options

are to minimise the need for possessions. In practice this

can be minimised but not altogether eliminated as in most

instances some form of trackside access is usually

required. As a result, design and detailing is becoming

more complex as special emphasis is being placed on

designing out the need for possessions through

innovative methods, such as the need for staged rivet

removal and erection of plates whilst trains run

unrestricted.

Therefore, the residual strength of individual

components/alternative load paths needs to be fully

understood when removing riveted connections, and

when introducing strengthening plates, special attention

to staged tightening of new connections will be necessary

to prevent initiating locked in stresses.

In terms of risk of possession overrun, it is subjective

either way as to whether strengthening or renewal

presents a greater risk, and throughout the design

process, factors that influence the risk are either designed

out or reduced to an acceptable and manageable level.

Strengthening is often piecemeal and can be curtailed at

relatively short notice provided that appropriate mitigation

measures are in place and the original strength of the

structure/component is restored prior to handing back the

possession. Alternatively, a complex strengthening

scheme may require substantial removal of existing

components that necessitate the need for the complete

reinstatement or some form of temporary works to be in

place prior to handing back.

Conversely, with a deck replacement, by the introduction

of designed 'fit up' tolerances and complete trial erection,

the risk of overrunning the possession should be

significantly reduced. However, there are always the

'unknowns or unforeseen' that could potentially put a deck

replacement at risk from overrunning, such as crane

failure, weather, services etc..

Site constraints

Deck replacements require an appraisal of the existing

substructures and their foundations to determine the

acceptability of the change in load effects. Qualitative

appraisals are undertaken to evaluate the condition of thesubstructures to substantiate 'steady state' conditions

which are generally supported by numerical calculations,

to justify that peak bearing stresses have not significantly

changed.

 Abutment repairs may be necessary as a result of this

appraisal, in addition to checking temporary load

conditions to identify what mitigation measures (propping,

anchors, temporary lowering of fill) are required to prevent

the abutments from overturning/sliding.

It is more often the case that repair and strengtheningschemes require some form of access scaffold to be

erected to facilitate the work. When spanning over water 

courses, it is often the desire to support the scaffold

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Paper 2 Repair and Strengthening versus Renewal

Railway Bridges - Today and Tomorrow

Figure 5 - Rockingham St. Cross Girder 'Bottom Hat' Strengthening

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platform from the structure rather than support within the

water course. This by itself may be prohibitive due to the

fact that more load is being added to an already sub

standard structure and the 'Project Team' must take a

view to see if the increase in load significantly affects the

operational railway. This may necessitate the need for phasing of the works or imposing temporary speed or load

restrictions for the duration of the works.

 A common advantage that repair and strengthening has

over renewal is that significant lead in times for plate

ordering or shop fabrication is not normally required, due

to its piecemeal nature. Where the scope of works is not

fully understood and repairs of a generic nature are

programmed, solutions can be fabricated relatively quickly

adopting 'off the shelf' plates and sections in order that

they can be erected in time to meet possession/road/river 

closure constraints.

 A large number of existing bridges have restricted

clearance and no refuges signs attached to them. Deck

replacements introduce the opportunity to improve the

safety of line side access and track geometry/gauging.

Other factors that may or may not affect the choice and

need to be considered are:

• Stakeholders/Third Party Interfaces

• Planning/Listed Building Restrictions

• Statutory Undertakers services and the requirement

for protection/diverting around the works

• Overhead Electrification and whether it can be left in

place during either strengthening, or more likely during

removal of existing and installation of new bridge decks

• DC Third Rail and access required to strengthen

girders positioned within the 'six foot'

• S&T, Power Cables and the requirement for 

protection/diverting around the works

• Environmental conditions, watercourses, SSSI,

Protected species, bats etc.

• Requirement to improve headroom or the need for 

collision protection beams to prevent mechanical

damage to exposed vulnerable elements

• Requirement to remove undesirable features, such as

wheel timbers, cast iron supports etc.

• Requirement for reapplying waterproofing to the deck

The very fact that structures where remote or difficult

access exists are often in poor state of repair and are up

for implementation due to the complexity in undertaking

previous routine maintenance tells its own story. Where

works are programmed to these structures, the solutions

adopted should either be very low maintenance or have

provision to access the structure for inspection and to

allow routine maintenance in the future to prevent

subsequent deterioration.

Conclusion

There is no straightforward answer on the decision

whether to repair and strengthen or renewal a bridge

asset.

Subject to funds and possession availability, structures

will generally fall into three categories:

• Bridges that are weak and obviously life expired are

replaced

• Bridges that are generally of sound condition and can

be repaired and strengthened at reasonable cost

• Bridges that are marginal:

Generally weak and uncertainties with condition but

can be repaired and strengthened at a cost. The site

however incorporates significant other key

determining factors that detract from reconstructing,

such as: access, impact on rail infrastructure and

third parties, track form, location etc.

The feasibility and evaluation process provides us with

useful information to enable an informed decision to be

made as to whether a structure should be repaired andstrengthened or renewed. However, marginal decisions

may be formulated on a qualitative basis or engineering

 judgement or some other unique overriding factor.

Cost Efficiencies could be made by advancing code

knowledge and/or by advancing the present work on

generic repair details to capture generic strengthening

details, both traditional and novel, to reduce the scope or 

number of strengthening and renewal schemes. It is also

worth noting that Network Rail currently have an ongoing

commission to identify the need for and development of 

further Standard Design Details for replacementunderbridges.

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Paper 2Repair and Strength ening versus Renewal

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Figure 6 - Abutment propping during deck replacement

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Railway Bridges - Today and Tomorrow 23

Paper Three

Jamestown Viaduct - Innovative

Strengthening of an Early Steel Viaduct

Robert Dale and Andrew Hanson

CORUS RAILWAY INFRASTRUCTURE

SERVICES

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Background

Jamestown Viaduct was constructed between 1887 and

1890 as part of the Forth Bridge Railway. It is believed to

have been designed and constructed by the engineers

responsible for the world-famous Forth Rail Bridge,

located a short distance to the South.

Jamestown Viaduct is situated between NorthQueensferry and Inverkeithing stations. The line over the

viaduct forms an important link for long-distance traffic

from Edinburgh to Dundee and Aberdeen, and for 

commuter traffic from Fife into Edinburgh. The line is also

used by a significant amount of freight traffic, principally

coal being transported to Longannet Power Station.

The viaduct comprises six spans. The four main spans

have early steel superstructures of 33.4 metres span and

approximately 70 degree skew supported by masonry

piers and abutments. A single masonry arch span pierces

each abutment. Each span of the steel superstructures

comprises two simply supported main truss girders with

cross girders supported on the top chords in turn

supporting railbearers. Asteel deckplate fixed to the top of 

the cross girders and railbearers supports ballasted track.

The cross girders, railbearers and deck plates are

believed to have been replaced in the early twentieth

century.

The Rosyth Dockyard branch line railway passes beneath

Span 2 and Span 4 crosses the B981 public road. The

bridge soffit is approx. 16m above the rail level of the dock

branch line railway and 12.8m above road level. The other 

spans cross open ground.

Because of its height and location, Jamestown Viaduct is

a significant landscape feature and was given 'Category

B' listed building status by Historic Scotland in 2004.

Structural Capacity

Network Rail Scotland has responsibility for ownership

and maintenance of the structure. A structural assessment

carried out by Babtie Group in 2000 on behalf of Network

Rail had found that the main trusses, including both top

and bottom chords, were overstressed.

This assessment was undertaken in accordance with the

then current Railtrack Code of Practice RT/CE/C/015

which used 'permissible stress' criteria. With the advent of 

the new 'limit state' Network Rail Assessment Code

(RT/CE/C/025 - Issue 2), Atkins Rail were commissionedto carry out further assessment work. Their report was

issued in October 2004. The findings of this assessment

were broadly similar to those of the earlier assessment in

terms of deficiencies in capacity of the metallic spans.

 A brief summary of the dynamic capacities of the various

elements of the bridge are shown below:

Top Booms RA1

Bottom Booms RA1

Ties RA0

Struts RA10Cross Girders RA7 (Shear)

The masonry piers, abutments and arch spans were also

assessed and considered to be adequate.

The report also noted that the paint system had broken

down, allowing moisture to penetrate through to the

steelwork, causing severe corrosion in places.

Strategy for Strengthening

 An eight day blockade had previously been arranged for 

repair and repainting works to be carried out on the Forth

Rail Bridge during late July 2005. Network Rail recognised

an opportunity to take advantage of this blockade to also

carry out works to Jamestown Viaduct, and instructed

their Civils Framework Contractor, Mowlem, to develop

proposals for a strengthening scheme with this in mind.

Network Rail and Mowlem jointly organised a value

management workshop at which a number of 

strengthening and reconstruction options were

considered, with the aim of increasing the capacity to

RA10 at a linespeed of 40mph. Following further 

24

Paper 3Jamestown Viaduct - Innovative Strengthening of an Early Steel Viaduct

Railway Bridges - Today and Tomorrow

Figure 1 - Aerial Photograph of viaduct.

Figure 2 - West Main Truss Girder Top Boom, showing poor 

condition of paint system and resultant corrosion

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discussion, three main options were identified:

• Strengthening of existing superstructure by adding

new steelwork to existing members

• Install new spine truss/beam between existing truss

girders

• Post-tensioning of existing main truss girders

In order to investigate the potential sub-options for the 3

options identified at the value management workshop, it

was agreed that the framework delivery team would ask

shortlisted civil/structural engineering consultants to

tender for the design services element of the Jamestown

project. The tender was prepared in such a way as to

encourage innovative proposals.

Seven completed tenders were received from the

shortlisted consultants and these were appraised and

scored based on a number of factors, including:

• Buildability

• Cost

• Risk

• Programme duration

• Railway possession usage

• Railway temporary speed restriction requirements

• Effects of work on remaining structure

Because of the viaduct's listed building status,

preservation of the existing structural form was also a

significant objective.

Two options were identified and proposed by Corus as

part of their submission:

• Strengthening by the addition of a new central truss

girder beneath each of the spans to support the cross

girders at their mid point and to relieve the existing

truss girders by pre-loading

• Removal of the track and ballast and replacement

with an in-situ reinforced concrete slab designed to act

compositely with the existing steel truss girders and

incorporating a direct fastening track system

Strengthening of the existing steel members was

considered, but a practical solution was not considered

possible because of the amount of additional

plates/sections that would have had to be added to the

existing sections, and in the case of the top chord of the

truss in particular, the obstructions formed by the

connections to other members at the truss nodes.

Complete reconstruction was considered but rejected on

the grounds of the much higher cost and short timescales

available for implementation using the 8 day blockade.

 A second value management workshop was held and it

was agreed that the option to be taken forward should be:

"Installation of new composite deck and plating

repairs/strengthening works to the existing structure"

Network Rail then produced a report on the second value

management workshop which was then adopted as the

Project Brief and included within the Project Definition

Document.

The composite solution proved attractive in that itsignificantly reduced the extent of strengthening work

required to the existing steelwork and preserved the

overall appearance of the original structure. It also met all

of the project requirements in terms of buildability, cost,

risk, programme, possession usage and temporary speed

restriction requirements.

By employing value management and value engineering

to agree the scheme selection, the project team identified

the best value option which met the aspirations of the

project, thus ensuring efficient investment to allow

continued unrestricted operation of the railway over theviaduct.

Scheme Development

Composite structural action between the reinforced

concrete slab and the existing structure was designed to

be achieved by welding 8,600 shear studs to the existing

deck plates and by the addition of steel diaphragm panels

between the deck plate and main truss girder top chord in

order to transmit shear between the deck plates and top

chord of the main truss girders. The rows of shear studs

were aligned parallel to the existing railbearers above the

main trusses and to the existing cross girders.

The condition of the existing deck plates would not be

revealed in its entirety until the track, ballast and existing

waterproofing were removed early in the blockade. During

the early stages of scheme development site

investigations were carried out, including trial pits on thebridge deck, which showed the deck plates to be in

relatively good condition at the locations exposed. Further 

random non-destructive testing of the deck plates showed

25

Paper 3 Jamestown Viaduct - Innovative Strengthening of an Early Steel Viaduct

Railway Bridges - Today and Tomorrow

Figure 3 - Shear Studs welded to deckplate above main

girder top flanges and cross-girders

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the thickness of the plates

to be acceptable. To

prove the feasibility of 

welding the shear studs to

the deck plate, trials were

carried out during the site

investigations by welding

a small number of shear 

studs to the areas of deckplate exposed in the trial

pits and testing the

connection of the studs to

the deck plate. These

trials were wholly

successful and proved

the strength of the

connections would be

adequate.

It was considered that there was still a risk of previously

undetected corrosion and other defects to the deckplatebeing revealed once the deck was exposed in its entirety,

and a supply of steel repair panels was fabricated

complete with studs already welded to them to cater for 

this eventuality.

Overloading of the deck plate by construction plant and

equipment during the blockade was also identified as a

risk and detailed calculations carried out to determine the

allowable level of loading on the deck. Restrictions on the

size and position of plant on the deck were also enforced

to ensure the deckplate was not damaged.

Testing of the original

metal used in the

construction of the

viaduct was also

undertaken to assess the

problems likely to be

encountered in welding to

the original steelwork.

The installation of the

concrete slab and

diaphragm panels

eliminated the need tostrengthen the top chords

of the main truss girders

by plating and also

significantly reduced the

extent of strengthening required to the other members.

 A departure from the design code was also agreed to

allow the shear capacity of the cross girders to be

enhanced by the addition of the concrete deck slab, thus

eliminating the need for further steelwork strengthening.

The main truss endposts, bottom chords and the diagonalties within the first three bays at each end of each girder 

were all found to be overstressed. The existing ties

comprised pairs of steel plates and strengthening was

achieved by the addition of new steel H-section struts

dimensioned to fit between

the existing ties. Welded and

bolted gusset plates

connected these members to

the existing truss bottom

chord and vertical members.

This strengthening also

partially relieved the load on

the truss end posts whichwere strengthened by the

addition of steel plates

welded to the external faces.

The bottom chords were also

found to be overstressed and

strengthening comprised the

addition of lower flange plates

welded to the existing

members to convert the open

section to a "U" shape. Careful detailing was required to

ensure that the trough created would drain and not allow

water and debris to pond, thus accelerating corrosion.

The skew ends of each span are supported by trimmer 

trusses, the top chords of which support the trimmed

cross girders. The trimmer trusses frame into the end

posts of the main truss girders. These trimmer trusses

required strengthening to support the new deck slab, and

this was achieved by the addition of steel plates and

sections welded to the existing members. Several

members also required replacement due to extensive

corrosion of the original steelwork.

Many of the existing plan and

vertical bracing members

were overstressed and rather 

than strengthening the

existing members, new

replacement sections were

designed, including the

temporary works required to

facilitate installation.

Many of the existing bracings

and associated gusset plates

were heavily corroded and

repair details were developedfor various scenarios

anticipated from the available

inspection and assessment

records. Detailed inspections

were carried out by Corus once access scaffolding was in

place and the extent of condition-led repairs agreed with

Mowlem and Network Rail. These inspections also

allowed detailed templating to be undertaken so that steel

sections could be fabricated off-site in "shop" conditions.

The design model was used to investigate the stability of 

the structure at all stages, which was particularly critical toprioritise the sequence of works and agree loading

restrictions, etc. at the various stages of the work.

The existing steel lattice girder parapets were retained to

26

Paper 3Jamestown Viaduct - Innovative Strengthening of an Early Steel Viaduct

Railway Bridges - Today and Tomorrow

Figure 4 - Installation of new diaphragm plates in the apertures

between the top boom of the main truss girders and the deckplate

Figure 5 - Installation of new struts in the end panels of the

main truss girders

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preserve the appearance

of the viaduct, but had to

be raised by the addition

of a tubular rail supported

300mm above the top of 

the existing parapet. A

new steel ballast plate

was designed to retain

the increased depth of ballast and prevent

spillage through the open

latticework. This also

removed the lateral

loading from the ballast

onto the existing lattice

parapet. Steel mesh

panels were also installed

to prevent ballast from falling onto the public road beneath

the viaduct.

The original deck drainage system comprised a series of steel pipes on a grid pattern hanging vertically from the

deck between the main trusses. A number of these pipes

were severely corroded or missing. Construction of the

deck slab required removal of the existing pipes and the

whole system was replaced with outlets located at the

ends of each span which discharge the drainage water 

clear of the steelwork superstructure.

Permanent Way

The initial composite deck concept developed by Corus

included direct fastening track, with the rails supported in

special baseplates fixed to the new reinforced concrete

deck slab. This matched the construction depth of the

original structure and only

marginally increased the

dead loading. The track

over the viaduct is curved

and quite heavily canted.

The practicality of 

achieving the required

track tolerances during

the main blockade was

discussed in detail withthe client and considered

to be a significant risk

considering the short time

available for construction

of the deck slab. Concern

was also expressed

regarding the transition

zone at each end of the viaduct, where the deck slab

interfaces with the much more flexible conventionally

ballasted track. Track maintenance is generally difficult in

the transition zones, particularly where the alignment is

curved and lateral forces cause the ballasted track tomove, creating a kink in the alignment of the track at the

deck end.

From a maintenance

perspective, Network Rail

preferred to retain ballasted

track over the viaduct and

Corus were asked to

investigate the feasibility of 

lifting the proposed rail levels

to accommodate this. A lift of 

approximately 400mm wasfound to be required across

the bridge in order to maintain

adequate ballast depth

beneath the sleepers to

permit mechanical

maintenance. Further 

modelling of the structure was

carried out and demonstrated

that the additional weight of the ballasted track could be

accommodated by the design. Steel sleepers were

employed to minimise both the combined weight of the

track and ballast and the ballast depth.

 A new permanent way alignment was designed by Corus

to accommodate the required track lift over the viaduct.

This was complicated by the existing 1 in 70 gradient and

the curved horizontal alignment. To run out the lifts in

compliance with permanent way design standards meant

that the length of track affected extended well beyond the

extremities of the viaduct itself and onto the approach

embankments.

The approaches to the viaduct are on major 

embankments, and geotechnical investigations and

stability checks were carried out by Corus to ensure that

the proposed track lifts would not adversely affect the

embankments. Immediately

beyond the ends of the

viaduct, precast concrete

retention units were designed

to support the raised ballast

levels in the cesses. Checks

were also carried out to verify

the stability of the spandrel

walls of the masonry arch

spans.

 A colour light signal is located

 just off the North end of the

viaduct on the Northbound

(Down) line. Checks were

required to confirm the extent

of alterations required to the

positioning of the signal head

to ensure that the track lift did not adversely affect the

sighting of the signal by drivers of approaching trains. The

final design involved raising the height of the signal head

by means of a spacer and refocusing the signal head.

27

Paper 3 Jamestown Viaduct - Innovative Strengthening of an Early Steel Viaduct

Railway Bridges - Today and Tomorrow

Figure 6- The original proposal for the superstructure strengthening,

showing the direct fastening track system on the concrete slab deck

Figure 7 - The revised proposal for the superstructure strengthening,

showing the ballasted track, new ballast plates and raised parapets

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Implementation

The design and implementation programmes overlapped

because of the tight timescales and the need to carry out

inspections and surveys. Mowlem commenced work on site

during April 2005. Scaffolding was erected to all four of the

main steel spans to provide access for surveys and

inspections and the critical steelwork strengthening works.

Corus engineers carried out surveys to verify dimensions

and identify the scope of the repair works required to each

span. Lanarkshire Welding were employed by Mowlem as

the steelwork subcontractor and they were highly pro-active

in value engineering and buildability studies with the client

and designer.

The steelwork repairs and strengthening were categorized

into work which had to be carried out before, during and

after the main blockade. The new struts were required to

cater for the additional weight of the concrete slab and

ballasted track, and together with the diaphragm panels,

had to be installed before the blockade.

Site access was complicated by the need to negotiate with

neighbouring land owners for access and positioning of site

compounds. Further restrictions were placed on the project

team by the presence of a designated site of Special

Scientific Interest (SSSI) on the South abutment andapproach embankments. Spans 3 to 6 are adjacent to a

new Park & Ride site, including a multi-storey car park

which was completed in May 2005. Site compounds were

constructed to the North West and the South East of the

bridge; the latter also providing vehicular access to track

level for the work to be carried out during the blockade.

Railway power, signalling and telecommunication cables

were present across the bridge and were carried in a

troughing route attached to the Eastern parapet. Various

cabinets containing relays and switching equipment are

located in the cesses at each end of the viaduct. All thecables were investigated to determine whether any were

redundant and the others were slewed clear of the works at

deck level during the main blockade and reinstated upon

completion.

During the main possession, Network Rail also identified

the opportunity to upgrade the signalling system in the area

as part of a separate project. Close co-operation between

the two project teams allowed this additional investment to

go ahead and to share some costs between the two

projects, thus providing financial efficiencies to both teams.

The concrete mix design for the construction of the deck

slab was critical. It had to combine a rapid gain of strength

whilst retaining a suitable "working time" to allow placement

and also be suitable for pumping. Corus provided a

specification, including the strength requirements at each

critical stage of the works and Mowlem investigated the

various options, finally selecting a micro-silica mix designed

by Tarmac Topmix. The concrete was placed by pumping

from ground level (using the largest concrete pump in the

UK). Trials were carried out in advance of the blockade to

prove the practicality of pumping to the required height

without affecting the properties of the concrete.

The steel reinforcement for the deck slabs was

prefabricated in panels in advance of the blockade,

designed to allow final adjustment if required when

positioned on the deck. The existing movement joints in the

steel deck plates at the ends of each span were retained

and incorporated into the new concrete decks.

During the main blockade (23rd July to 1st August 2005)

approximately 20,000 man hours were worked. This

included:

• Removal of existing track, ballast and deckwaterproofing

• Cleaning of existing deck

• Welding of shear studs to deck

• Fixing 120 tonnes of reinforcing steel and formwork

• Placing 600m3 of concrete

• Installing ballast retention units to all 4 corners of the

viaduct

• Installation of new waterproofing new drainage systems

28

Paper 3Jamestown Viaduct - Innovative Strengthening of an Early Steel Viaduct

Railway Bridges - Today and Tomorrow

Figure 8 - Placing of the concrete was achieved using alorry-mounted pump at road level

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Railway Bridges - Today and Tomorrow

• Installing new ballasted track over the viaduct

• Lifting and re-aligning track on the approaches

The work was carried out using two shifts of 12 hours

each to achieve 24 hour working throughout the blockade.

Corus provided continuous design support on site during

the blockade to ensure that any technical issues could be

dealt with quickly and efficiently.

Work continued on site after the blockade to complete the

outstanding steelwork strengthening/repairs and

repainting of the whole structure. As the viaduct has close

engineering links with the Forth Rail Bridge, Network Rail

agreed with the local authority planners to paint the

viaduct in "Forth Bridge Red" to match its bigger brother.

This also sits well with the local authority's aspirations to

have the whole area designated as a "World Heritage

Site".

Conclusion

The project to strengthen Jamestown Viaduct has been

successful because of the integrated approach by the project

team. The design concept was unusual and is thought to be

the first project to achieve railway bridge strengthening using

a composite reinforced concrete slab on a truss bridge. All the

relevant parties involved in the strengthening work worked

closely together to ensure that the project achieved Network

Rail's aspirations and construction issues were given a high

priority during development of the design to ensure that the

final solution could be implemented efficiently. This was

achieved through formal and informal value engineering

involving all of the relevant parties.

Design work commenced in January 2005 to a very

challenging programme dictated by the availability of the

8 day blockade in late July 2005. This required all parties

to co-operate to ensure that the necessary approvals

were obtained efficiently at each of the design stage

gateways. A detailed design risk assessment was also

prepared in order to ensure all design risks were both

transparent and managed.

The overall cost of the scheme was £5.3 million. The

project has successfully met all the objectives previously

set:

• Cost effectiveness

• Preservation of the original structural form

• Minimisation of disruption to railway operations

• Achievement of the short design and construction

programme

• Capacity of the bridge increased to RA10 at 40mph

linespeed.

The project has been nominated for numerous awards

including the 2006 British Construction Industry Awards

and the National Railway Heritage Awards, and has been

shortlisted for the 2006 'Prime Minister's Better Public

Building Award'.

29

Figure 9 - Upon completion of the strengthening works, the viaduct was painted in 'Forth Bridge Red' to emphasise its links with the Forth Rail Bridge

Paper 3 Jamestown Viaduct - Innovative Strengthening of an Early Steel Viaduct

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30 Railway Bridges - Today and Tomorrow

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31Railway Bridges - Today and Tomorrow

Paper Four 

Innovative Techniques Used in the Life

Extension Works of Leven Viaduct

Jon Tree

CARILLION

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1.0 Introduction

Leven Viaduct is a 460m long, twin track, 49 span structure

traversing the Leven estuary at the point it merges with

Morecambe Bay. Constructed in 1857, the viaduct’s original

composition was wrought and cast iron. Decks consisted of 

2½' deep, simply supported girders and piers were

constructed from multiple 10½" diameter circular columns.

The original structure was designed with slender sectionsto minimise the imposed loads from wind and tides.

 As a result of the ongoing corrosion incurred from the

marine environment, the viaduct has been subjected to a

number of refurbishment and strengthening works prior to

the project described in this paper. These have included the

conversion of all forty-eight piers from cast iron columns to

concrete and brick leaf piers, the replacement of span 37

over the shipping channel, the installation of sheet piles to

protect permanent channels between piers and a number 

of smaller routine maintenance items.

In July 2005, Carillion Rail were appointed to replace the

entire superstructure to the viaduct. This was required due

to loss of section from corrosion and change in design

codes. Also included in the contract were brickwork repairs

to all 48 piers and the construction of reinforced concrete

robust kerbs and anchor slabs at either end of the structure.

 At a cost of £10.5m, the work was successfully completed

within a 16 week blockade between March and July 2006.

The purpose of this paper is to record some of the technical

challenges faced and innovative techniques developed

during the planning and construction process.

32

Paper 4Innovative Techniques Used in the Life Extension Works of Leven Viaduct

Railway Bridges - Today and Tomorrow

Figure 2 - Aerial view of Leven Viaduct

Figure 1 - Works i n progress

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2.0 History

Developed as part of a conceptual scheme initiated by

George Stephenson to create a railway around

Morecombe Bay, the Leven Viaduct was constructed by

contractors W & J Galloway for the cost of £18,604.

Initially constructed as a single track, the viaduct was

designed specifically to assist widening at a later date to

accommodate dual tracks.

Site investigation prior to construction failed to establish

the presence of bedrock beneath the estuary bed and it

became apparent that the structure would have to be

founded on sands that were 'readily driven away by the

wind when dry'. Various foundations were considered but

the final design was one of 10½" hollow, circular columns

with 2½' discs at the base.

Piles were installed from rigs mounted to moored

pontoons. The method of installing the piles was very

innovative for the time and the subject of much interest.

Once positioned, water was pumped through a hose in

the middle of the pile to an orifice in the centre of the 2½'

discs at the base. This jet served to displace the sands

beneath the pile which, when combined with an applied

alternating rotatory motion, allowed two piles to be driven

to a depth of 6½m at the ebb of a single tide.

The girders for the deck were floated intoposition on pontoons and installed with a

travelling crane. At approximately twice

the length of other spans, span 37 was

constructed in the form of a manually

operated drawbridge to allow the passage

of shipping vessels in the channel beneath

(this was eventually replaced for a fixed

deck around 1904 to comply with new

standards). Rock armour in the form of 

rubble-stones were tipped around the

base of the piers to protect against tidal

scour.

In the early part of the twentieth century, considerable

difficulty was experienced in the maintenance of the

viaduct due to constant breakages in the columns around

low water level. Whilst the cast iron performed well both

below and above sea level, accelerated oxidation was

experienced in tidal zones subjected to constant wetting

and drying action.

In 1915, steel caissons were sunk around the six columnsthat made up each of the forty-nine piers and filled with

concrete. With the tops of these caissons at approximate

low water level, the remaining column encapsulation

could be constructed from a 5 course thick brick shell and

also filled with concrete.

With the columns encapsulated, timber trestles were

floated out on high tides and erected either side of 

individual piers. These were wedged under the soffit of the

girders to carry the dead weight of the deck and railway

traffic. The tops of the columns were then cut away and

the columns filled with grout. Bedstones and new bearings

were installed before lowering the

decks girders and removing thetrestles.

This project took five years of single

line working to complete.

33

Paper 4 Innovative Techniques Used in the Life Extension Works of Leven Viaduct

Railway Bridges - Today and Tomorrow

Figure 3 - Archive photo of or iginal viaduct, showing John

Galloway in the centre

Figure 4 - Original pier design

Figure 5 - Archive drawing, showing the conversion of piers

from cast iron columns to bri ck and concrete leaf piers

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3.1 Access Design and Instal lat ion

Due to the confined, linear nature of the site, access was

identified as one of the key activities in the safe delivery of 

the 2006 refurbishment. The following items were

recognised at the planning stage as requiring their own

access:

• Soffit access for new deck installation• Pier repairs

• Edge protection during demolition

• Mobile cages for bearing installation

• Cantilevered walkway to maintain a walking route the

length of the viaduct

The first access required was that for replacing the

existing walkways. 'Up and over' pier end scaffolds were

hung from both bullnose ends of each pier. These

provided a platform 900mm beneath the top of the

bedstones to assist when burning out the existing

bearings, drilling and grouting new bearings and installingnew walkways.

In order to undertake the brickwork repairs, access was

required to the full height of the piers (approximately 6m).

The tidal range at the viaduct varied from nominal, ankle

deep water at low tide to 2m from the deck soffit on spring

high tides. A system was required that would both

withstand the tides and allow access to different levels on

the pier depending on the water level at any given point.

 A horseshoe pontoon arrangement was considered that

would fix around the piers and rise and fall with the tides.This was rejected however due to the time restraints it

imposed on the work. Pier repairs would not be feasible

as the tide came in because materials would wash away.

 Access to the top section of the pier would be then

restricted to the two hours taken for the tide to go out. The

25 hour cycle of the tides would have also constantly

disrupted shift times.

Remaining soffit access for replacing the main decks was

designed as a boarded walkway spanning from the north

pier end scaffold to the south (1200mm beneath top of 

bedstone). Originally designed to be fixed to the pier end

scaffolds, it was observed that by hanging these on chain

blocks they could serve as both soffit access and a

platform on which to execute pier repairs (similar to those

used for window cleaning). In practice these platforms

could be lowered or raised the full height of the pier in less

than ten minutes, although care had to be taken to

observe tide times and keep the platforms in the elevated

position when not in use.

 At its peak, the construction program required four 

walkways and two decks to be removed a day, resulting in

up to 60m of exposed edge at any given point. Edge

protection was designed as a cantilevered walkway,

drilled and fixed into the existing long timbers by 'hop-up'

brackets.

In areas where decks and walkways were being removed,

barrier tape was erected to demarcate the zone and

custodians positioned to prevent unauthorised access.

Personnel inside the 'exposed edge' zone were instructedby the custodian on the safe walking route and all

personnel adjacent to an edge wore harnesses clipped

onto safety lines.

Once a deck was removed, access was required to

prepare the bedstone and install the new bearings. Mobile

cages were constructed that could be lifted and moved by

road railer as required.

3.2 The Use of Gantries to Replace Decks

To facilitate the replacement of Leven Viaduct'ssuperstructure, each of the 48 spans was considered as four 

members: north walkway, north deck, south deck and south

walkway.

Various means were considered for cutting out the original

structure, including oxyacetylene, oxypropane and plasma

cutting. Thermic lances were eventually chosen as the

preferred method due to their speed, resistance to the

elements and ability to reach difficult spots. Existing

walkways were removed and new installed by tandem lifting

from the adjacent line with road railers.

Tandem lifting was also considered for removing the existingdecks. This was rejected however as whilst 12T rail mounted

Plasser cranes had the capacity, the existing deck girders

would not take the applied point loads from the crane's axles.

The final deck installation scheme adopted was two track

mounted gantries. Calculation proved the proposed walkway

section capable of bearing the applied load from a gantry

whilst lifting the heaviest deck unit. A track system was then

designed with a 120mm square box section compatible with

the gantry supplier's leg skates and with a fixing detail to the

new walkways.

Gantry rail sections were then fabricated in 5m lengths with

male/female connections at each end. By 'hay making' these

from the back to the front of the gantry, the gantry could be

34

Paper 4Innovative Techniques Used in the Life Extension Works of Leven Viaduct

Railway Bridges - Today and Tomorrow

Figure 6 - Deck soffit access, including 'up and over' pier 

end scaffolds and mobile, unit beam platforms

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moved the length of the viaduct. Both gantries had motorised

lifting equipment and were moved laterally along the viaduct

by duel operated tirfirs.

Once sufficient new walkways had been installed, a 50T

mobile crane was erected on the west abutment (Ulverston).To avoid in-depth investigation into the capacity of the

existing abutment, a temporary works scheme was

developed that would limit the bearing pressure applied by

the 50T crane to those experienced from the existing rolling

stock in use. Two number 9m long, 1m wide, 400mm deep

reinforced concrete slabs were fabricated and installed in the

up and down line cess for the crane outriggers. With the

crane erected on the abutment and two spans of gantry track

in place on the walkways, the first gantry was constructed on

span 49 (the first span at the west end of the viaduct). This

took 6 days due to strong winds, however in fairer weather it

may have been completed in 3 days.

The first gantry then proceeded east, removing upline decks

and placing them on roadrail trailers on the down line for 

removal to Ulverston Station. The second gantry was then

constructed on span 49. This followed the first gantry,

installing new upline decks once the new bearings were

installed.

Once both gantries had reached the east (Cark) end of the

viaduct, they swapped roles and returned to the Ulverston

abutment removing and replacing the down line as they

went. The return journey was found to be significantly faster 

(up to five decks installed in a day) as the gantries were not

impeded by scaffold erection (this was all erected in the

upline phase) and the six foot had been removed, reducing

the amount of burning.

3.3 The Use of Direct Fastening Vipa

Baseplates

Before the project, the track was fixed to the deck by means

of long timbers running parallel and fixed to the rail with

traditional baseplates. However, with the maintenance costs

for these timbers escalating due to the limited availability of timber of the required quality, Network Rail were keen to trial

an alternative system.

The system proposed by Network Rail and eventually

realised by Carillion was one of Pandrol VIPA-SP Rail

Fastening Plates bolted to 70mm thick steel stools at 600mm

centres.

The benefits of this system included:

• Reduction in vibration transferred into the deck and piers

due to the internal dampener within the VIPA baseplate

• Reduction in re-radiated noise (use of these baseplates

on a similar structure in Norway was found to reduce

noise levels by 14 dB(A))

• Low vertical stiffness (20 kN/mm) resulting in greater 

distribution of axial point loads from rolling stock, therefore

reducing the required capacity from the deck members

• Improved installation tolerances (+/- 1mm in line and

level achievable)

• High electrical resistance which reduces the chance of 

circuit problems

• Quick and easy to replace without the need to cut the

rail

From the outset, Network Rail were keen to adopt a 'top

down' procedure for positioning the vipa plates. The use of 

40m long slave rails was considered at the planning stage as

a method of aligning the baseplates on the stalls. This was

rejected however due to the requirement for additional road

rail resource (all be it part time) to move these rails about.

To simulate the slave rails, two jigs were designed and

fabricated that fitted snugly into the vipa baseplates at the

correct gauge. The first jig consisted of two cradles shaped

to receive pipe lasers, one cradle along the centre line of 

each rail. The second jig contained brackets to receive

perspex laser targets, also positioned along the centre lines

of the rails. By setting out the start and end of any length of 

vipa baseplates by traditional methods (total station and

dumpy level), the laser jig could be set to the centre lines of both rails and the target jig used to line and level all the

intermediate baseplates. The use of lasers instead of slave

rails also reduced manual handling risks to the workforce.

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Figure 7 - Gantry and gantry track, fixed to the walkways Figure 8 - VIPA plates and Pandrol stools

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3.4 Plant and Mater ial

Logistics

Prior to Carillion's tender, the

Life Extension Works were

originally anticipated to be

executed over two 16 weeks

blockades a year apart.

However, by developing the

high level methodology

described in 3.2, Carillion were

able to produce a programme

condensing the project into one

blockade.

To reassure Network Rail that

the proposed methodology was

achievable, detailed hourly

programmes were prepared for 

repetitive activities such as

deck installation. These werethen subjected to QRA

(Quantitive Risk Assessment)

analysis to investigate the

impact of certain activities (such as scaffold erection, deck

burning etc) taking longer than anticipated or being

delayed. Whilst the program had very limited float, the

QRA analysis produced sufficiently positive results to gain

the clients confidence.

In brief, the methodology consisted of removing existing

walkways and transporting them to Cark station. Here the

scrap would be unloaded by crane ready for collectionand the RRV loaded with a new walkway to return to the

viaduct. Once back, the new walkway was installed, the

RRV loaded with another scrap walkway and the process

repeated. Walkway replacement proceeded on both the

up and the down line simultaneously at a rate of two each

side a day. With all walkway traffic travelling east to Cark,

new and old decks were free to be transported out of 

Ulverston in the west.

In order to achieve the required output of four walkways

and two decks replaced in a day (actually exceeded in the

later phases of the contract), 'dispatch and receive' zones

were implemented between the viaduct and Cark and

Ulverston Stations. These were clearly demarcated and

each zone exclusively controlled by a machine controller 

who would authorise and record all plant movements in

that zone. Pedestrian access was strictly forbidden in

these zones and only one machine allowed in at any

point.

With all road rail plant either occupied with deck or 

walkway installation (or trapped between the two), it was

apparent at planning that any material or plant deliveries

during the day would disrupt production. For this reason,

a dedicated resource of 2 RRVS and 4 men wereallocated as a 'load out' gang, operating between 6pm

and 9pm after each shift. Their duties included moving

tools and equipment to where they were required for the

following day, delivering consumables (gas, water, fuel

etc), moving gantry track, tidying up and removing surplus

materials. The production achieved in the day shift was

found to be directly proportional to the success of the

previous nights 'load out'.

 At 5pm after every shift, the senior members of the project

team (including Project Manager, Senior Engineer, Senior 

Supervisor and Client) would meet to review the daysprogress and agree the work for the following day. A 'Daily

Coordination Sheet' (described in more detail in 4.0) was

then prepared for the following day and issued to the

Engineering Supervisor for briefing and further distribution

to COSSs and machine controllers.

3.5 The Refurbishment of Span 37

Site investigation and analysis into the existing span 37

prior to tender had identified that the existing deck was of 

sufficient capacity and condition to warrant refurbishment

rather than replacement. The decision was taken by

Network Rail that this was the preferred option and

Carillion proceeded on their instruction.

The greatest challenge faced with this operation was the

removal of the existing lead paint without pollution to the

estuary. Over and under scaffold similar to that used on

the other spans for soffit access (but without the chain

blocks) was erected the full length of the span.

The scaffolding was then fully encapsulated in a material

called EnviroWrap. This recyclable fabric, similar in

appearance to viscuine (except white), could be heat

sealed together in panels around the outside of thescaffolding. Further heat was then applied to the entire

membrane, causing it to contract and become taught, like

the surface of a drum. Whilst more expensive than

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Figure 9 - Example of a Daily Work Plan

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traditional monoflex sheeting, this system gave a more

thorough, robust encapsulation from which very little dust

escaped.

With the existing steel blasted (with care taken not to overload

the soffit scaffold with blast debris), the span was inspected to

reveal that little repair was required other than a small amount

of work to the stiffeners on the main girders. With this

complete, new deck plates were bolted to the existing crossbeams, new pandrol rail support stalls fixed and new

walkways hung from the outside girders. The original steel

received an XM92 paint specification.

Had span 37 been remote to the rest of the project, the works

could have been executed significantly faster. However, due

to its location, access had to be maintained for the movement

of deck sections to and from the gantries. To facilitate this, one

track had to be live for the majority of the operation, essentially

making the refurbishment two separate tasks (up and down

line) rather than one.

In its final state, the downline walkway was required to carry

three 11Kv United Utility cables in a trough beneath the durbar 

walkway plates (diverted from the existing galvanised UU

trough that was to be removed within the scope of works).

Unfortunately, the contract programme required the cables to

be diverted before the installation of the new walkway.

Due to their size and relative stiffness, the cables had to

installed within 75mm of their final position before United

Utilities would divert the power and allow Carillion to

commence removing the original galvanised duct route from

beneath the new south walkway legs. A temporary works

scheme was adapted that hung the cables in a suspended

trough 75mm above their final place of resting within the new

walkway, thereby allowing the diversion to take place. The

new walkway was then installed about the UU cables before

removing all temporary works and lowering the cables into

position in a one hour outage. Great care and rigorous site

briefings were then undertaken to protect the live cables in the

south walkway for what remained of the contract.

3.6 Deck Art icu lat ion and the Use of  

 Anchor Slabs

Whilst archive drawings existed for the original structure, the

horizontal load transfer from deck to deck was unclear. Each

span consisted of simply supported girders housed in

channelled iron bearing pads. Spans appeared to be bolted

together at their main girder webs in groups of five. However,

whatever movement may have originally been

accommodated, it had long disappeared as the bearings

rusted over and became composite with the main girders.

In order to imitate the existing articulation and minimise the

transfer of horizontal live loads into the existing piers, the

decks were designed to transfer loads from one deck to

another by means of communal bearing plates betweenspans. Each bearing plate consisted of two pot bearings, one

fixed, the other with +/-4mm longitudinal clearance to

accommodate thermal expansion/ contraction of the 9m

spans. Any movement beyond this 4mm (caused by trains

braking, accelerating or thermal effects on the decks/rail)

would then be transferred into the next span and so on down

the viaduct.

Upon reaching the ends of the viaduct, means for containing

this horizontal force were required to avoid failure of the

existing abutments. New reinforced concrete sill beams were

designed and constructed to receive the four end span's

bearings. These sill beams were then stitched to reinforcedrobust kerbs (installed for train containment at the approach to

the viaduct) as well as mass concrete anchor slabs. The mass

of these anchor slabs (580T at Ulverston, 320Tat Cark) were

sufficient to absorb any applied horizontal load that had not

dissipated into the rest of the structure.

Whilst the new spans were designed to transfer horizontal

load along the length of the viaduct, the refurbished span 37

was not and subsequently represented a weak link in the

chain. In order to efficiently transfer horizontal loads from span

36 to span 38, two trusses (upline and downline) were

designed to prop the bearing plates either side of span 37,thereby bypassing the existing girders.

Each truss consisted of two number, 20m long, 300mm deep

I section beams. These were braced horizontally at 1.5m

centres by diagonal angle irons. The trusses (similar in shape

to unit beams, except larger) were floated into position

underneath span 37 on pontoons on a spring high tide. RMD

strongbacks were set across the top flanges of the main

girders above the track and tirfirs slung from these, with their 

wires extending through purpose drilled 30mm holes in the

new deck plates. By attaching eight tirfirs to each truss, the

trusses could be manually tirfed from the pontoons to their 

final position under the soffit of each line. Once in position, the

pontoons were retrieved to Barrow Docks and the trusses

welded and bolted into position.

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Figure 10 - Down line truss being tirfed into position fromthe temporary pontoon

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4.0 Health, Safety and Environmental

Management

Due to the nature of the project, the Leven Viaduct Life

Extension Works potentially included all the most serious

and frequent hazards faced by the construction industry.

These were not limited to, but included:

• Working at height (when the tide was out)

• Working over fast flowing tidal waters (with the tide in)

• Working in close proximity to road rail plant

movements

• Hot works, including welding and burning

• Repetitive manual handling

• Confined lifting operations

• Exposure to the elements

• Work in extremely environmentally sensitive areas

Each of the above hazards were identified at the planning

stage with robust, practical systems designed to mitigate

the risk. On site these risks were managed by ensuring all

personnel received an explicit induction explaining the site

rules, after which they were tested to confirm their 

understanding. All operatives also received regular 

briefings throughout the project.

Carillion also operate a system of BAT (Behavioural Action Teams) and SAG (Safety Action Group) meetings.

This is an effective method of involving everyone in the

management of Health, Safety and the Environment on

site.

BAT groups consisted of appointed artisans who would

meet once a fortnight to discuss and record what they

considered the most pressing HS&E concerns for the site

at that time. Representatives from the BAT team would

then attend fortnightly SAG meetings, at which their 

concerns would be tabled and also any other items raised

by the SAG team. The members of the SAG team

generally consisted of approximately one third artisans

and two thirds management, with subcontractors also

instructed to attend. The SAG meetings provided an

excellent means of opening lines on HS&E

communication from apprentice artisan up to Regional

Director.

 After close collaboration with Network Rail, the Method

Statement/Operating Plan procedures were modified to

suit the unique nature of the site. Method statements were

written for all site activities and briefed to the workforce on

a weekly basis as standard, however the site used daily

workplan sheets to authorise operations instead of weeklyoperation plans.

The daily work plan sheets (shown in 3.4) consisted of a

single A3 sheet on which a schematic of the site showed

all plant movements for the day, a more detailed diagram

of the viaduct showed the location of various gangs (e.g.

burners) as well as approved walking routes, names and

phone numbers of all key personnel, the tide times and

the day’s weather forecast.

Before accessing the site, all personnel received a COSSbriefing from daily work plan by the Site Access Controller,

with whom they signed on. They were then permitted to

access and work on the structure under the supervision of 

'territory custodians'. These were COSSs identified by

green hard hats, positioned approximately every 100m

along the viaduct. They protected operatives within zones

rather than individual gangs and were not required to give

additional briefings or collect signatures, as this had been

done by the Site Access Controller.

The use of daily coordination sheets and territory

custodians proved to be a very effective means of controlling safety on a heavily populated, linear site. In the

sixteen weeks of the project, with over 10,000 man days

of construction, there was not a single serious incident.

5.0 Conclusion

The Life Extension Works to Leven Viaduct provided an

opportunity to develop many innovative techniques in the

execution of the works. As to be expected, some of the

methods employed were more successful than others but

the lessons learnt on this contract shall be invaluable to

similar projects in the future.

Without doubt, a significant contribution towards the

success of the scheme was the relationship between the

client and principle contractor. By maintaining an open,

honest dialogue the project team were able to discuss and

resolve problems rapidly and often to mutual advantage.

Carillion's decision to involve subcontractors and client in

SAG and BAT meetings also generated a culture in which

everyone had equal responsibilities for health and safety

in the work place.

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39Railway Bridges - Today and Tomorrow

Paper Five

Development of Standard Designs and

Details for Railway Bridges

Jason Johnston

NETWORK RAIL

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 Abstract

The development and use of Standard Designs and

Details (SDD) is one of the steps taken by Network Rail to

improve network safety, asset reliability, and increase

efficiency. The focus of this paper is on the development

of SDD for footbridge and underbridge replacement

schemes.

The footbridge SDD is currently at the Approval in

Principle stage (GRIP Stage 4). The paper discusses the

rationale behind selection of the structural form. The

limitations of application in terms of span and clearances

are described along with details of the access options

provided.

The development of underline bridge SDD is currently in

the early design development stage (GRIP Stage 3). This

paper is being published part way through a Feasibility

Study aimed at determining the requirements for 

underbridge SDD. Formal peer review arrangements arein place to help guide the study and ensure robustness of 

the conclusions. Whilst this contracting strategy is

unconventional it is considered necessary as this work is

expected to have far reaching consequences for future

underbridge renewals.

The functional requirements of underbridges and an

understanding of a 'typical underbridge renewals profile',

based on recently completed schemes and schemes in

the Business Plan, is being used to guide the

development of SDD. The paper describes how Value

Engineering principles are to be used to shortlist bridgeforms and determine the optimum level of standardisation.

Keywords: Efficiency, Footbridge, Function, Safety,

Standard Design and Detail, Underbridge, Value

Engineering.

Introduction

The development and use of Standard Designs and

Details (SDD) is one of the steps taken by Network Rail to

improve network safety, asset reliability, and increase

efficiency. The main focus of this paper is on the

development of SDD for footbridge and underbridge

replacement schemes.

It is helpful to first look at the background to the efficiency

drive and the structured approach taken by Network Rail

to develop the library of SDD. Further supporting

information is provided on areas of design responsibility

around application of SDD on projects along with

discussion on the benefits of using SDD and the control

measures needed.

Background to Efficiency Drive

Network Rail has been set challenging efficiency targets

by the Office of Rail Regulation (ORR). Unit costs are

required to be driven down by 30% by the end of the

current five year control period in March 2009 whilst

simultaneously improving network reliability and safety.

Major Projects & Investment (MP&I) Civils are working

closely with the Director of Civil Engineering to meet this

challenge. The resulting Civils Efficiency Strategy sets

out the overall approach to achieve these target savings.

The strategy identifies twenty-seven initiatives broadly

under four main themes:

• Design and the development process

• Contracting and procurement

• Resource utilisation and productivity

• Culture

Two initiatives under the 'Design and the development

process' theme relate to the development and use of 

SDD.

Phased Development

The SDD are being developed in accordance with theGuide to Railway Investment Projects (GRIP) process and

procedures. A four phase approach has initially been

adopted with selected existing, territorially based SDD

developed first. The first issue of SDD (Ref. 1) in June

2006 focused on brick and masonry repairs and has been

issued both internally within Network Rail and externally to

our supply chain in CD-ROM format. The CD-ROM

contains the standard drawings, generic technical

approval Forms A and B, and technical user manuals.

The second issue of SDD (Ref. 2) in August 2006 includes

earthwork related SDD. Phases three and four covering

SDD for footbridges and underline bridges are planned for issue in 2007. It is intended that future issues will be

through a web based system.

Design Responsibi lity

Design responsibility for the application of SDD on

projects ultimately depends on the terms and conditions of 

contract. The terms relating to design responsibility in the

suite of Network Rail standard forms of contract are

unchanged following the introduction of SDD. In the case

of a construct only contract (with design completed under 

a separate professional services contract) Network Rail

accept responsibility for the design and appropriate

application of SDD. For design and construct contracts

the Contractor accepts design responsibility and for 

appropriate application of SDD.

Benefits & Controls Needed

The benefits of using SDD include:

• Reducing design development timescales and costs

• Adopting good practice in the design and detailing of 

Civil Engineering works

• Minimising contractor and sub-contractor costs

associated with uncertainties in detailing requirements

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• Reducing the volume and costs of Maintenance works

through the adoption of good practice

• Streamlining the Technical Approval process for 

commonly used designs and details

The development of a library of SDD also requires

controls to be put in place to ensure appropriate

application, continued use, and that they are kept relevantand up to date.

In order to ensure the appropriate application work

instructions (Ref. 3) have been issued to define the

Technical Approval process for using SDD in Civil

Engineering works. The work instructions supplement

Network Rail's requirements for technical approval as

defined in NR/SP/CIV/003 (Ref. 4). The work instructions

define both 'simple' and 'complex' applications of SDD.

Simple applications are where a generic Form A and a

project specific Form B are required for the application of 

SDD. In practical terms for bridge renewal schemes the'complex' category will more than likely apply whereby

project specific Form A and B are required.

Where demanded by the complexity of the SDD, a

Technical User Manual (TUM) will be developed to help

ensure appropriate use of SDD, particularly where there

are a number of standard elements which together 

comprise a solution. Footbridges and underbridges with

Medium or High level of standardisation are expected to

have a TUM.

 Appropriate application is further strengthened with each

set of SDD drawings containing an outline Designer Risk

 Assessment. The assessment considers the generic

hazards during design, construction and operation stages

and provides suggested mitigation measures. The risk

assessment is required to be developed by the scheme

Designer for any specific application of SDD on a project.

In terms of ensuring that SDD are used the Work

Instruction defines responsibilities of both the Client

(Asset Engineer) and the project Sponsor (Renewals

Engineer) to identify potential opportunities and for the

particular requirements to be agreed in the project remit.

The process of obtaining financial authority for projectswill be used to challenge investment papers - the

presumption being that SDD should be used unless it can

be demonstrated that use of non-standard design and

details is more appropriate. Existing business reporting

systems and the Cost Analysis Framework (CAF) will be

used to capture the use and associated benefits of SDD.

Feedback on the suitability of SDD is actively encouraged.

Feedback using the 'User Feedback Form' on the CD

(Ref. 1 & 2) will be periodically reviewed to ensure that the

SDD remain appropriate and reflect the needs of the

 Asset Engineers and the delivery teams. At appropriatestages the SDD library will be modified and extended.

Development of Footbridge SDD

The approach to standardising design and details is centred on

using current best practice which aims to strike the optimum

balance between function, cost and safety. The development

process began with a workshop to identify best practice across

a range of civil engineering works including 'non-station'

footbridge renewals. The workshop attendees comprised

Network Rail engineers from national and territory teams,consultants, framework contractors, as well as representatives

from the steelwork fabricator industry. The structural form

selected for the footbridge SDD is commonly referred to as the

'London Midland' type (Fig. 2). This is a proven solution with at

least 40 recently constructed as part of West Coast and Cross

Country Route Modernisation schemes.

The footbridge SDD is currently at the Approval in

Principle stage (GRIP Stage 4) and applies only for 'non-

station' renewals. The design covers a main span range

of up to around 25m (nominally spanning four tracks), with

both stair and ramp access options (Fig. 3). The main

span has two geometrical arrangements with and without

in-span stairs thereby providing an option compliant with

the Disabled and Discrimination Act (Ref. 5). In terms of 

vertical clearances the supports (either single column or 

two or four leg trestle) are detailed to enable use on lines

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Paper 5 Development of Standard Designs and Details for Railway Bridges

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Figure 1 - Example of the footbridge structural form adopted for SDD

Figure 2 - Typical section through footbridge main span

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with or without overhead electrification. The access

spans have two structural forms with a shorter spanning

'stringer beam' and a longer spanning 'truss'. The SDD

access options enable project teams to optimise the

number of supports based on site constraints. Options

are available for full or partial enclosure of the main and

access spans. The requirement to use such protective

measures will be determined by project level risk

assessment.

The footbridge SDD initiative has recently been extended

to enable application to non-mainline stations. Additional

features will include cable conduits, lighting provision, and

lift shaft accommodation.

Development of Underbridge SDD

The development of underline bridge SDD is currently in

the early design development stage (GRIP Stage 3). This

paper is being published part way through a Feasibility

Study aimed at determining the requirements of 

underbridge SDD. The following sections provide an

insight to the approach being taken including the

establishment of 'functional' requirements of underbridges

and use of the Business Plan to guide the study (Fig. 4).

The overall contracting strategy for the Feasibility Study is

fairly unconventional but is well suited to this project which

is expected to have far reaching consequences for underbridge renewals. Network Rail is working with Cass

Hayward and Partners LLP on the main study and has

also formally engaged a number of other leading

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Paper 5Development of Standard Designs and Details for Railway Bridges

Railway Bridges - Today and Tomorrow

Figure 3 - Typical arrangement of SDD footbridge showing stair 

and ramp access optionsFigure 4 - Process diagram showing principle activities in

Underbridge SDD Feasibil ity Study

Main Span

Superstructure

Main Span

 AccessStairs

 Access

Ramps

PLANScale 1:200

ELEVATIONScale 1:200

ELEVATION ON MAIN PLANScale 1:200

Main Span

SuperstructureMain Span Support

Superstructure

Stair/Ramp Support

Stairs &Columns Stairs &Columns25000 Column C/CRS

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consultants to review deliverables and provide guidance

during the study.

The formal peer review workshops are proving to be an

excellent opportunity to draw on the wealth of experience

of other leading consultants in this field. The peer 

reviewers comprise senior bridge engineers from within

Network Rail, Atkins, Hyder Consulting, Mott MacDonald,

Scott Wilson Railways, and Tony Gee & Partners. Thefirst of three 'Peer Review Workshops' was held in

October, with the last two planned in November and

December. The later workshops will be further supported

by leading fabricators from both the steelwork and pre-

cast concrete industries as well as representatives from

our framework contractors.

Establishing Functional Requirements of 

Underbridges

The first objective of the feasibility study was to establish

the functional requirements of underbridges. Thisinvolved consultation with key stakeholders along with a

review of the draft Network Rail standard on the design of 

bridges (Ref. 6). The functional requirements are

summarised in Table 1 against various categories

including normal operations, abnormal situations, and

also installation and demolition.

It is recognised that against each functional requirement

there are a number of related (parallel) issues that require

consideration. These have been identified as part of the

study but for reasons of brevity have not been included in

this paper. The functional requirement and associated

parallel issues, along with a set of agreed desirable andundesirable features will be used to assess bridge form

options for potential development as SDD.

Examples of Desirable Features:

• Sacrificial elements at steel/concrete or 

ballast/structure interface

• Simple robust steelwork details

• Early warning of distress

• Good run on/run off details

• Open stiffeners to steel deck plates

• No intermediate web stiffeners on track face

• Multiple bearing stiffener legs and protection to ends

of main girders

• Simple anti-uplift/displacement restraints

• Simple bearing arrangements

Examples of Undesirable Features:

• Hidden details

• Complex detailing leading to unnecessarily high

construction cost

• Box girders with difficult access

• Bird nest crevices

• Noisy rattling (loose) plates

• Expansion joints (short spans)

• Site welding

• Heavily stiffened thin steel plates

• Fatigue stress raising details

• Open deck floors

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Paper 5 Development of Standard Designs and Details for Railway Bridges

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Category

Normal Operations

 Abnormal Situations

(Unplanned)

 Abnormal Situations(Planned)

Installation/

Demolition

Functional Requirements

Capability to support load

 Acceptable deformation

Satisfy durability requirements

Satisfy structure gauge requirements,

and construction depth/headroomconstraints

Facilitate safe working environment

 Accommodate interdisciplinary

requirements

Satisfy operational requirementsEasy to manage

Sympathetic aesthetics

Bridge bash resistant

Capability to support derailment load

 Accommodate substructure movement

Capability to support on-track plant

loads

 Able to easily replace parts(maintenance or emergency)

Ease of construction (and eventual

demolition)

Table 1 - Summary of Underbridge Functional Requirements

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Underbridge Characteristics in Future Plans

The Network Rail Business Plan (Ref. 7) is used to guidethe development of SDD for underbridges. The definition

and certainty of the plan has been greatly enhanced over 

recent years due to considerable early investment in the

development phase of projects. The Business Plan

identifies 72 underbridge replacement schemes up to

March 2009. The breakdown of these between territories

and also the typical minimum and maximum span is

provided in Table 2 and Figure 5. The key characteristics

of these structures such as span, skew, available

construction depth, and installation constraints do not

form part of the Business Plan and had to be separately

sourced from the territory engineering teams.

Supplementary information from 64 recently completed

schemes is also used to improve the robustness of this

development tool (Table 2 and Figure 5). The details of 

schemes recently completed are based on data held

within the CAF. Together, the details of the schemes in

the Business Plan and those recently completed will be

used to establish a typical national underbridge renewals

profile. This profile will capture not only typical span

frequency, but construction depth (top of rail to deck soffit)

constraints and installation constraints, i.e. proportion

installed as one unit or multiple elements assembled in-situ. These three key factors are being used to guide the

development of SDD.

Interestingly, 25% of schemes involve spans less than

5.0m, 60% less than 10.0m, 80% less than 15.0m, and

90% less than 20.0m. The three peaks in the span versus

frequency plot centre on 3.5m, 7.0m and 12.5m. These

approximately coincide with square spans over 

accommodation access or single lane road without and

with pedestrian access, and a two lane road with

pedestrian access.

Based on the data collected almost all the structures

spanning over a road have sub-optimum headroom (less

than 5.7m) and are therefore potentially at risk of being

struck by road vehicles. This is consistent with the fact

that there are over 2000 annual bridge strikes incidents on

the network each year. This statistic, combined with the

often limited opportunities to adjust track levels, is

consistent with available construction depth being a key

consideration when replacing underbridges.

44

Paper 5Development of Standard Designs and Details for Railway Bridges

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Territory

LNE

LNW

Scotland

Southern

Western

15

22

8

11

8

1.8

3.5

3.6

1.9

3.1

48.0

23.1

41.5

24.7

13.2

34

5

7

19

7

2.4

7.8

2.5

2.0

3.1

35.0

19.1

10.7

26.0

13.7

4

1

2

8

1

No. Min. (m) Max.(m) No. Min. (m) Max.(m)

U/B Spans Recently

Completed (from 2002/03)

U/B Spans in Current

Business Plan (to March-09)

Entries with

incomplete

span data

Table 2 - Summary of spans of recently completed and future underbridge replacement schemes

(from 2002/03 to 2008/09)

Figure 5 - Spans of recently completed and future underbridge replacement schemes (from 2002/03 to 2008/09)

Span (m)

   F  r  e  q  u  e  n  c  y

   (   N  o .

   S  p  a  n  s   )

T w oL  an eR o a d 

 (  wi   t  h  p e d  e s  t  r i   an

 a c  c 

 e s  s  )  

T w o

L  an eR o a d 

 (  wi   t  

h  o u t  

 p e d 

 e s  t  r i   an a c  c  e s  s  )  

A  c  c 

 om o d  a t  i   on /  

 S i  n gl   eL  an d R o a d 

 (  wi   t  h  o u t  

 p e d 

 e s  t  r i   an a c  c  e s  s  )  

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Based on national feedback from the territory engineering

teams the installation methodology for recently completed

schemes (and that expected for future schemes) consists

of around 60% installed as one unit either using a crane

or transporter, with the remaining 40% involving assembly

of multiple elements in situ.

Further validation of the Business Plan data and 'typical

national underbridge renewals profile' will be undertakenby comparing the output from Network Rail's concurrent

Route Availability (RA) project. The first phase of that

project will be completed at end of December and any

relevant findings fed into this project.

 Assessment of Potent ial Solut ion Types

The feasibility study will consider the degree to which

existing SDD, commonly used designs and details, and

other potential solutions (for example reinforced and/or 

pre-stressed concrete) meet the requirements for 

function, as well as economy and safety.

The recommendations on which options should be

developed as SDD, along with the optimum level of 

standardisation will be established using qualitative 'Value

Engineering' techniques.

Preferred Solution Types

The value that each solution (X) represents will be

determined using the ratio of its function over cost as

shown in Equation 1. It is expected that the value each

solution represents will vary with span. Therefore theassessment is expected to be based on specific span

ranges (S) e.g. 1.8m< S5 ≤5m, 5< S10 ≤10m, 10< S15

≤15m, 15< S20 ≤20m, and 20< S30 ≤30m.

The level of functionality achieved for each solution (within

the applicable span range) will be based on the

summation of scores against the weighted functional

requirements, parallel issues and level of 

desirable/undesirable features. The cost element for each

solution type will be based on whole life considerations

but normalised against the lowest cost solution. It should

be noted that these value assessments will not only

consider existing bridge forms but also modifications to

such forms as necessary to reduce the number of 

'undesirable' features.

The solutions to be short listed for SDD will be based on

those representing best value. The aim is to ensure that

adequate and overlapping SDD coverage is provided for 

the typical national underbridge renewals profile.

Ensuring that the SDD options overlap in terms of span

range, construction depth and buildability options

provides Asset Engineers and delivery teams with a

limited range of options to meet typically encountered site

constraints.

Optimum Level of Standardisation

 Against the short list of best value options each will be

further assessed to determine the optimum level of 

standardisation. The Value of Standardisation (Y) will be

determined for three potential levels: Low, Medium or 

High. The value that each level of standardisation

represents will be determined using Equation 2.

The Low level of standardisation is expected to comprise

examples of best practice standard details only, whilst at

the other extreme the High level will involve the full design

of all principal elements similar to the existing 'box girder'

SDD (Ref. 8). The Medium level will involve partial design

of principal elements similar to existing 'Z' Type SDD (Ref.

9). Other factors to be taken into account include the

Frequency of SDD usage which will be determined using

the Business Plan data as a guide, and Savings expected

to accrue from each application. The Cost factor relates

to the capital investment needed to develop Option X SDD

with Y level of standardisation.

Conclusions

The development and use of SDD is one of the steps taken

by Network Rail to improve network safety, asset reliability,

and increase efficiency. The focus of this paper is on the

development of SDD for footbridge and underbridge

replacement schemes.

The footbridge SDD is currently at the Approval in Principle

stage (GRIP Stage 4). The paper discusses the rational

behind selection of the structural form. The limitations of 

application in terms of span and clearances are described

along with details of the access options provided.

45

Paper 5 Development of Standard Designs and Details for Railway Bridges

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Equation 1

Value (X)s =Function (X)s

Cost (X)s( )

Equation 2

Value (Y) =Frequency x Saving (Y)

Cost (Y)( )

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The development of underline bridge SDD is currently in the

early design development stage (GRIP Stage 3). This paper 

is being published part way through a Feasibility Study aimed

at determining the requirements for underbridge SDD.

Formal peer review arrangements are in place to help guide

the study and ensure robustness of the conclusions. Whilst

this contracting strategy is unconventional it is considered

necessary as this work is expected to have far reaching

consequences for future underbridge renewals.

The functional requirements of underbridges and an

understanding of a 'typical underbridge renewals profile',

based on recently completed schemes and schemes in the

Business Plan, is being used to guide the development of 

SDD. The paper describes how Value Engineering principles

are to be used to shortlist bridge forms and determine the

optimum level of standardisation.

References

1. Network Rail CD-ROM of Civil Engineering Standard

Designs and Details, NR/CIV/SD/CD/1 (Issue 1) June 2006

2. Network Rail CD-ROM of Civil Engineering Standard

Designs and Details, NR/CIV/SD/CD/2 (Issue 2) August

2006

3. Network Rail Company Standard NR/WI/CIV/151

'Technical Approval of Standard Designs and Details for Civil

Engineering works, (Issue 1) April 2006

4. Network Rail Company Standard NR/SP/CIV/003

'Technical Approval of design, construction and maintenance

of Civil Engineering infrastructure' (Issue 2) April 2004

5. The Disability Discrimination Act 2005

6. Network Rail Company Standard NR/SP/CIV/020 "Design

of Bridges & Culverts" (Draft)

7. Network Rail Business Plan 2006/07 (August Period 5)

8. Railtrack PLC, Standard Half Through Underbridges,

Steel Box Girders and Transverse Ribbed Floors, 1996

Revision of Design

9. Railtrack PLC, Standard Half Through Underbridges Z-

TYPE Girders & Composite Deck, 1996 Revision of Design

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Paper 5Development of Standard Designs and Details for Railway Bridges

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Figure 6 - Span Range and Structure Depth of Various Bridge Forms (based on Peer Review 1 Information Pack by Cass

Hayward & Partners LLP) N.B. Thickness of bars is indicative of relative structure depth (top of deck to soffit)

Span (m)

Extent of 

European use

Construction Depthincreases with span

Construction Depth varies withspan and form

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47Railway Bridges - Today and Tomorrow

Paper Six

Delivery of Works - Safely

Ray Ekins

 ALFRED McALPINE PROJECT SERVICES

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 Across the Network Rail (NWR) Western territory from

London, west to Penzance and North West to Pwllheli on

the Cambrian Coast, are extensive sections of track that

are prone to damage and or speed restrictions. These are

often a result of failing sea defences, falling rocks from

escarpments or faces within deep cuttings, unstable

embankments & cuttings, poor drainage, and lastly,

timber, steel, cast iron, concrete, stone or brick bridges

and associated structures being at their safe working limitand approaching the end of their working life.

In the last 4 years under the Western Territory Framework

 Agreement (WTFA) until recently known as "GWESPA"

(Great Western Earth Works & Structures Partnering

 Arrangement), Alfred McAlpine Project Services (AMPS)

has worked at over 400 locations across this territory,

putting 3 million man hours into many varied schemes.

Currently a team of NWR and AMPS staff (10 & 50 people

respectively) are based in Stonehouse, with a further 104

directly employed on site and various subcontractors.

Civil Engineering challenges include working adjacent to

the railway, tidal estuaries, sea front locations, rivers,

inaccessible locations, geological issues, environmental,

ecological, weather, structural etc. As a result of these

challenges there are resulting complex safety &

environmental issues which need to be incorporated into

the project.

The purpose of this paper is to explain how we deliver 

these works safely and in an environmentally friendly

manner whilst meeting NWR's other requirements, i.e. on

time and to budget, all factors being paramount to the

continued success of the project.

Safety is simply an integral part of the operation. Very few

issues are just "safety" or "environmental"; this approach

has been the key of successful project delivery which

currently enjoys nearly 600 days without a serious

accident and an AFR of 0.0.

• The project encourages joint and collaborative working

with NWR, sub-contractors, statutory bodies etc. and

ensuring a safe and healthy work force and public

• Whilst AMPS recognise NWR's needs and difficultieswe have to ensure the process from the advice of work

packages through to the issue of project Health & Safety

files satisfies legislation, the NWR and AMPS

requirements by ensuring adequate Planning,

Organisation, Control & Monitoring is given

• We also have to satisfy our ISO9001, 14001 &

OHSAS18001 accreditations and maintaining our RSC,

CAC and Linkup certifications

• We use an integrated AMPS & NWR system

Broadly, the process is as follows:

• Initially NWR develops a Works Package of Civil

Engineering remediation needs. This may be because of 

long term Temporary Speed Restrictions as a result of 

Track Quality Problems or gradual slope failure or small

rock falls (where the failing face was covered in

vegetation) and thus not visible, has alerted NWR to

potentially severe problems. This was the case at

Winterbourne and most recently at Chipping Sodbury

cuttings where urgent resolutions of the problems were

required. The timing of the works can also be dictated to

by the availability or not of railway Possessions. A "Form A" is produced by AMPS to agree in principal the concept

of work and envisaged methodology, and is accepted by

NWR. Project delivery can commence up to two years or 

more before any physical works start

• The issue of the Work Package starts the process and

 AMPS are responsible for collating from the NWR

archives and other sources information on the site,

existing structures and services

• In liaison with our Designers the remit is reviewed. The

design has to ensure that unacceptable risks are notintroduced to the railway whilst ensuring efficiencies can

be made. Design Risk Assessments are produced and

submitted with a "Form B" for detailed design to AMPS,

together with Commercial, Safety & Environmental Risk

 Assessments and target costs. If significant changes are

made to the design a "Form B Addendum" is issued

• The procurement process is initiated for our Sub-

Contractors and material suppliers which meet the

relevant Linkup, CHAS (Contractors Health and Safety

 Assessment Scheme) & AMPS requirements and

depending on the nature of the works will give specialist

advice and occasionally prepare detailed method

statements and risk assessments

• Running parallel to the above is the Health & Safety

Plan (known as Project Management Plans [PMP] within

 AMPS). This is developed including detailed planning of 

the operation; further possession planning is undertaken

by AMPS. Method statements and Risk Assessments

are written by Alfred McAlpine and the contractor and

reviewed by NWR. Staff are also identified and any

resultant training needs are resolved. "Form C" for 

Temporary Works are also produced unless these are

complex in nature and if so are done at the Design stage

• With everything prepared, men, materials, facilities and

plant etc. are mobilised for the start of the works. As

many as 25 sites may be running at one time

• On Completion of the works or possession (may or may

not be in stages) a "Form E" is issued, during this time

the Health Safety File is being developed for handing

over to NWR

• With the site clear, the works move into the

maintenance stage

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The following gives examples of Planning, Organisation,

Control, Monitoring & Review undertaken across the

project supplemented with additional safety improvements- AMPS Business Management System and the Safety

Observation Stations.

Planning

Incorporates: Possession Planning, Design, Ground

investigation, Environmental, appropriate approval forms,

target price, construction stages and commissioning.

With a supporting team of 5 persons under the Senior 

Planner, Primavera P3 Planning software is used to

control the planning of approximately 70 sites per year,

with a value ranging between £100k to £8.0m. Planningcan commence up to 2 years before construction stages.

Some work packages have such delaying problems as

awaiting DTI approvals due to environmental constraints.

Typical problems include:

• Temporary works have to be kept to a minimum and

where they are required, these works are incorporated

into the program at the earliest possible stage to ensure

they are not rushed and are produced in a safe and

timely manner 

• Sub contractors are identified and communicated withfrom the earliest possible time in the program lifecycle.

Making them aware of our safety culture and policies

ensures that a good safety record is maintained on site

• Completing the design of schemes as early as possible

allows engineers the necessary timescales to produce

Health and Safety plans and method statements within a

safe and timely manner 

Organisation

With all NWR and AMPS staff centrally based within a two

storey building located in the heart of the geographicalarea covered by the project and working along side each

other, an excellent inter-working between all parties has

been achieved, thus ideas can easily be floated, issues

resolved and delays in communicating between one office

and another have been reduced. Within easy walking

distance are some of the Designers again who can

provide an excellent interface to the project. Nearby are

the heavy stores facilities provide for a ready supply

whether for emergency or routine works a variety of 

instantly available materials.

With a multifaceted workforce of whom several are SafetyCritical (COSS, ES, IWA & Machine Controller) they are

also trained to CPCS for Plant, CSCS for safety, Lifting

Operations, Confined Spaces etc.. They and the sub-

contract staff are supervised by General Foremen then

Sub-Agents followed by Agents (many of whom are

approved by NWR as CREs), supported by the Works

Manager who reports directly to the Project Manager.

We have made a conscious decision to employ as many

of our staff and workforce as possible. We have 75

directly employed staff and 4 sub-contract commercial

staff.

Our workforce is set at 10% above the minimum planned

requirement (allowing for sickness and training). The

shortfall is made up as labour only sub-contractors who

are generally hand picked from three main companies.

Our direct workforce is 68 strong at present.

Over the last 41/2 years we have built up a good safety

culture within the organisation. The provision of good

training, equipment and PPE has shown a reciprocal

commitment by the workforce. Having a direct labour 

force is cost effective, as multi-skilled our men can

operate dumpers, then rollers etc.. The initial trainingcosts are out weighed by resource effectiveness as most

operations are not manual.

Controlling

The Project Quality System complies with BS EN ISO

9001 2000 and applies to all work undertaken by the

 AMPS, our consultants, sub-contractors and suppliers.

The Construction Team has the primary responsibility to

deliver and verify quality by planning, controlling and

checking their work. See Appendix 1.

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Figure 1 - Chipping Sodbury cutting

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Monitoring

 All activities are monitored using various methods;

examples noted below include Health & Safety, Quality

and Measurement of our Performance.

• To ensure the project is compliant to many safety

standards we are subject to constant monitoring by

ourselves, NWR and other organisations. These includeyearly NWR project management audits & Contractor 

 Assurance Case audits, supported by site inspections by

their staff. In addition to these we are subject to BSI and

other body's audits as part of our accreditation

processes. We also monitor ourselves with Directors,

Safety Advisors and Site Management undertaking site

audits. The Railway Safety Case is independently

audited yearly and the supporting documents internally

audited yearly also. AMPS also audit the management

systems. Lastly we audit our safety critical suppliers of 

plant and people and assess all other supply companies.

The principal aim is two fold: one, to identify failings

against the relevant standard and, two, to identify good

practice which can be utilised across the company.

• Monitoring of the works is also undertaken through the

development and implementation of Quality Control

Plans. These identify key stages of the works which are

subject to inspection and test processes

• Another form of monitoring is the Key Performance

Indicator (KPIs), these consider:

Contractor Accident Rate

Result of NWR Safety Engineer's Site Inspections

On-site Quality

Train Minute Delays

Progress

Efficiencies

Review

 As each work package draws to a close, progressively

 AMPS and NWR review all areas as part of a continual

improvement process, such as:

• Accident and Incident review has formed a key part to

their reduction. Since commencement of the project all

incidents & accidents whether near miss, minor or major 

have been reviewed at site, at Stonehouse and at

respective headquarters and forms part of our safety

culture. The review process includes site teams, Rail

Operations Group meetings, NWR / AMPS ProgressMeetings, AMPS QUENSH (Quality, Environmental,

Safety and Health) & Directors Meetings. Serious

incidents which are, or potentially are RIDDORS are

subject to an ARC - Accident Review Circle - this is a

 joint meeting between the injured, witnesses, Site

Supervision & management, Principal QUENSH Advisor 

and Director and if the injured party is a sub-contractor,

his Director is invited.

• Statistical analysis is undertaken by headquarters and

locally providing useful drivers to identify problems and

then target these with adequate H&S resources toresolve them as shown on the diagram in Appendix 2.

Examples of this include the Glove Policy and Eye

Policy. The former was a forerunner to Network Rail’s.

• The review of Health & Safety audits previously

mentioned is again critical to improving long-term safety.

Since January 2004 all site inspections with any

resulting corrective actions have been logged; these

total 1386 including recommendations. All corrective

actions are graded and reviewed with the Health &

Safety Advisors and site teams, at the joint Network

Rail/AMPS progress meetings, Rail Operations Groupand others. One outcome has been the steady decrease

in findings whether by AMPS or Network Rail staff based

on man hours worked.

You will notice within Appendix 3 that problem areas have

included access, the Construction Phase Health & Safety

Plan, house keeping, plant and waste.

• An Achilles heel to safe working practices is attitudes

and perception by all persons. To assist the Project

Manager, a questionnaire is issued to all site staff 

annually to seek their view whether they strongly agree

or disagree to the safety questions posed. This was the

initial Behavioural Safety Initiative at GWESPA, coupled

with Safety Committee meetings; they provide a valuable

communication tool to all parties to ensure the workforce

voice is heard and therefore safety improved. Within

 Appendix 4, is the questionnaire containing 30 questions

with the results for this year. This questionnaire was

developed by the SQE team to give the workforce a

chance to comment and provide management with

feedback on H&S issues. This year's results are being

currently analysed by the Project Manager to identify

target areas for improvement. An initial review indicates

though there is increased safety awareness Q30, we stillhave a long way to go as Q8, 16 & 25 would indicate.

• Lessons Learnt is an ongoing process, during the

weekly site meeting an outcome of a particular issue, for 

example, coping with unexpected changes in Ground

Conditions which has resulted in Design changes and

work content is reviewed for its success or failure.

• During the life of the project Safety Workshops have

been held at a nearby hotel where all grades of 

employee have been able to freely discuss problems

and assist in recommending improvements, receivesafety and environmental presentations.

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Safety Improvements

 AMPS has introduced or supported many safety

initiatives, e.g. company wide Drugs & Alcohol Policies,

Behavioural training, Worker involvement - MAD (Make a

Difference), 365, 1 day safety presentations held off site

including, Safety Net Videos, railway emergency drills,

work force medicals, Passport System for induction which

cuts costs on inductions particularly on Possessions, etc.. All have contributed to making the workplace safer.

Further examples new in 2006 are the supporting

processes - AMPS Business Management System and

the Safety Observation Stations.

1. AMPS Bus iness Management System

 AMPS manage project delivery with the aid of an

integrated business management system introduced in

spring 2006 to bring together all the different disciplines

within one controlling system and are an underpinning

management tool. This combined approach replaces theformer SHEMS system which as the title suggests only

considered Safety, Health & Environment.

Figure 2 shows the integrated Business Management

System, which consists of nine manuals.

Project Management Plan

 A key component is the Project Management Plan for 

projects - this defines how we will manage a project. All

the information required to complete the project in line

with Railway Safety & Standards Board Standards, NWR

Company Standards, AMPS company standards, project

requirements and legislation.

Figure 3 shows the Project Management Plan, which

consist of four sections.

• Section C - Defines common arrangements and

requirements for QUENSH

• Section S - Specific requirements for Health & Safety

• Section Q - Specific requirements for Quality

• Section E - Specific requirements for Environmental

• Project File - QUENSH Records

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Paper 6 Delivery of Works - Safely

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Figure 2 - Integrated Business Management Syst em Figure 3 - Project Management Plan sections

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Rail

This Rail Procedures Manual contains Procedures to aid

 AMPS to work on NWR's infrastructure in a safe and

compliant manner, in recognition of requirements

contained within the Contractors Assurance Case,

Railway Safety Case and Linkup. These procedures are

supported by Rail Standard forms, Guidance forms,

Training, Risk Assessments and Work Instructions.

The Rail Procedures Manual also interfaces between

RSSB & NWR standards and AMPS Business

Management System. It comprises the following sections:

• Rail Procedures

• Appendix A - Rail Standard forms

• Appendix B - Rail Guidance notes

• Appendix C - Rail Training

• Appendix D - Rail Risk Assessments

• Appendix E - Rail Work Instructions

2. Safety Observati on Station

These are A1 size boards (see Appendix 7) with loose

cards for safety improvements and near misses to be

reported. They are to be used on all sites from early

October and they should:

• Encourage reporting of near misses and safety

improvement suggestions by all persons on site

• Provide simplified near miss reporting

• Record safety improvement suggestions from

employees

• Give a format for giving feedback

• One system across all projects

 Any suggestions that will improve QUENSH management

are to be raised, for example:

• Method of working

• PPE

• New materials

Interpretations

• An unplanned event that did not result in injury, illness,

damage, environmental impact or product loss - but had

the potential to do so

• The difference between a near miss and an

incident/accident can be a fraction of a second or a few

millimetres that may not be there the next time

• Near misses are warnings of accidents in the making

Reporting

By reporting these warnings and looking for their causes,

we can help prevent incidents/accidents. Typical items

include:

• Behaviour - ignoring site rules/procedures

• PPE - damaged or not used

• Slips, Trips & Falls - untidy work area• Poor Supervision - uncontrolled plant movements

• Lifting & carrying - kerbs lifted by hand

• Environmental Issues - dust & noise from plant

• Danger to the Public - uneven temporary footpaths

• Traffic Management - signs/cones blown over 

• Access & Egress - obstructed walkway

• Excavation - no supports

• Plant & Equipment - speeding, poorly maintained

• Work at Height - no edge protection

• Hazardous Substances - unmarked/open container 

• Services - mechanical excavation too close

See also Appendices 5 & 6.

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53

Paper 6 Delivery of Works - Safely

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 Appendix 1 - Quali ty Control Arrangements

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54

Paper 6Delivery of Works - Safely

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 Appendix 2 - Breakdown of Accidents and Incident on WFTA

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55

Paper 6 Delivery of Works - Safely

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 Appendix 3 - Health, Safety and Environmental Audit Findings

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56

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 Appendix 4 - Health and Safety survey

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57

Paper 6 Delivery of Works - Safely

Railway Bridges - Today and Tomorrow

 Appendix 5 - Lessons Learnt

 Appendix 6 - Near Miss Report ing

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Paper 6Delivery of Works - Safely

Railway Bridges - Today and Tomorrow

 Appendix 7 - Safety Observation Board

 A near miss is where it all starts so

Share It and Stop It!

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59

Paper 6 Delivery of Works - Safely

Railway Bridges - Today and Tomorrow

 Appendix 8 - Typical schemes

Chepstow rock face

River Yeo br idge

Patchway cutting

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60 Railway Bridges - Today and Tomorrow

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Railway Bridges - Today and Tomorrow 61

Paper Seven

Track/Bridge Interaction and Direct Track

Fixing

 Alan Monnickendam

CASS HAYWARD

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62 Railway Bridges - Today and Tomorrow

Introduction

The presence of a bridge within a length of continuously

welded rail results in the rail being subjected to the

following effects:

• Additional stresses due to structural deformation as a

train crosses the bridge

• Additional stresses due to the thermal movement of the

deck

In addition, under traction and braking longitudinal loads

are shared between the rail and the bridge deck.

The mutual influences of bridge and rail structural

behaviour are known as Track/Bridge Interaction (TBI).

This paper describes analyses used to investigate these

phenomena with reference to recent experience of 

bridges with direct track fixing systems.

The need for TBI

Hitherto rail stresses due to these effects were generally

regarded in design as being within acceptable limits by

satisfying the structural deformation criteria specified in

UIC 776-3R (Deformation of Bridges). However, where

headroom requirements demand particularly slender 

structures these limits often cannot be achieved. Also, the

more widespread use of direct track fastening systems

often results in deck configurations which are out with the

limits of applicability of the rules contained in thisdocument.

Where such a situation arises a more rigorous approach

is required which often results in a specific interaction

analysis being performed. This involves modelling the

structure, the rails and their connection to the bridge deck

and a length of normally supported track off both ends of 

the structure. These calculations are generally

undertaken using the guidelines given in UIC 774-3R

(Track/Bridge Interaction - Recommendations for 

Calculations), which also specifies the limits which have to

be achieved for the various criteria, including rail stresses,

rail movements relative to the deck and deck movements

relative to adjacent decks or embankments.

It should be noted that this document also provides a set

of simplified rules which, if satisfied, will obviate the need

for a more complex analysis. Some of these have also

been embodied in Appendix G of EN1991-2 (Actions on

Structures - Part 2: Traffic Loads on Bridges).

Direct Track Fixing Systems

The most common types of modern direct track fixingsystems are usually referred to as the embedded rail

system and the discrete baseplate system.

The embedded rail system involves setting the rail in a

preformed trough within the structure and surrounding it

with a pourable resilient compound which cures over time

to provide continuous vertical and horizontal support to

the rail. The main advantage of this system is the degree

of flexibility it allows to achieve the correct vertical and

horizontal alignment of the rail over the bridge. It appears

to be more suited to short span bridges due to concerns

over the time and expense involved in removing andreinstating longer sections of resilient material and track in

the event of a rail breakage in the future.

Discrete baseplate systems rely on a fabricated baseplate

to provide support to the rail at appropriate intervals

depending on the track category, and generally utilise a

bolted connection to attach the rail to the structure.

Whilst offering support more consistent with conventional

ballasted track, this system is much less flexible in terms

of both vertical and horizontal alignment and requires

significantly greater attention to construction tolerances

than the embedded rail system.

Bridges incorporating both systems have been

constructed in the UK within the last year.

The Behaviour of the Track

In undertaking a track/bridge interaction analysis it is

necessary to model the horizontal connection of the rail to

the structure as well as the appropriate vertical support

stiffness. For discrete baseplate systems the horizontal

connection behaves in a non-linear manner and depends

on the type of fixing adopted. Essentially the resistance

of the track to longitudinal displacement increases rapidly

at low levels of displacement and remains constant once

it has attained a certain value (Fig. 1).

Paper 7Track/Bridge Interaction and Direct Track Fixing

Figure 1 - Relationship between resistance of the track to mov ement and longitudinal displacement

Resistance of 

the track k

Longitudinal displacement of the rail u

Scatter range

of curves

Theoreticalrelationship

(bilinear)

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63Railway Bridges - Today and Tomorrow

In the analysis this is represented by a bi-linear relationship. This form of relationship is also appropriate

for the modelling of the sections of ballasted track off the

structure. Figure 2 shows how the relationship for 

ballasted track varies for different conditions of loading

and ballast. A linear relationship is adopted for embedded

rail systems.

Suggested values of resistance for direct track fixings are

given in the UIC document or values obtained by testing

of specific units may be available from the manufacturer.

Modelling

In view of the bi-linear nature of the longitudinal

connection stiffness a track/bridge interaction analysis

requires the adoption of non-linear analysis methods.

In addition to acceleration/braking and thermal actions,

the model must be capable of accurately representing the

rotation of the deck ends under vertical live loading and

the associated horizontal movement due to the vertical

offset of the bearing from the neutral axis of the deck.

The analysis will provide information on rail stresses,

longitudinal bearing reactions, displacements of the railrelative to the structure and forces on fixings.

Case Studies

Recent bridge designs utilising direct track fixing have

raised a variety of issues in relation to track/bridge

interaction.

Wellington Road (NEC1/24) and Ladgate

Lane(MBW1/11)

Wellington Road U/B (Newcastle) and Ladgate Lane U/B(Middlesborough) were originally conceived as similar 

structures for deck reconstruction, but the former was

eventually constructed to a different design. Both are

short span bridges, 9.0m and 9.8m respectively, withheadroom constraints requiring minimum construction

depth. The solution proposed involved the adoption of a

precast concrete filler beam deck with preformed troughs

to accommodate an embedded rail system. The main

difference between the two structures was that Ladgate

Lane was skewed at approximately 23 degrees to the

road below compared with the square span at Wellington

Road.

 As the Wellington Road structure satisfied the

deformation criterion of UIC 776-3R no further 

consideration of rail stresses was required. The skew at

Ladgate Lane was accommodated by continuing the

embedded rail for a short distance off the bridge to provide

a square transition back to ballasted track. Although

Ladgate Lane was of very similar proportions, the fact that

the direct track fixing continued off the structure meant

that it was outside the limits of applicability of UIC 776-3R.

This document states that rail stresses should be

determined by direct calculation for structures of this form.

 A track/bridge interaction analysis was undertaken for this

structure which predicted that additional rail stresses

would be within the acceptable limit of 72N/mm2.

The new structure was installed during a possession atChristmas 2005 (below).

Paper 7 Track/Bridge Interaction and Direct Track Fixing

Figure 2 - Resistance/Displacement relationships for ballasted track

Figure 3 - Ladgate Lane following reconstruction

Resistance (k)

of the track

(kN/m)

Resistance of the rail in sleeper (loaded

track) (frozen ballast track without

ballast)

Resistance of sleeper in ballast only

(loaded track)

Resistance rail in sleeper (unloaded

track) (frozen ballast or track without

ballast)

Resistance of sleeper in ballast

(unloaded track)

Displacement (mm)

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64 Railway Bridges - Today and Tomorrow

Selby Canal (TCW1/21)

Selby Canal Bridge is a 36m single span structure

carrying the Doncaster to Selby line over Selby Canal

approximately 1 mile to the south of Selby town centre.

The existing bridge, which carries twin tracks on

longitudinal wheel timbers is scheduled for reconstruction

in 2007. Two schemes have been developed for thisstructure, one utilising the embedded rail system, and the

second using the Pandrol Vipa discrete baseplate system.

Ultimately it is the latter that has been selected for 

implementation. Due to the length of the structure and the

fact that the directly fixed track continued off the bridge to

accommodate the large skew (55 degrees) track/bridge

interaction analyses were undertaken for both options.

One of the objectives was to ascertain whether it would be

possible to replace the existing jointed track with CWR.

 Analysis of both schemes showed that if CWR were

installed without an expansion switch at one end of thebridge then the rails would be overstressed under a

combination of vertical and longitudinal live loading and

extreme thermal effects.

Leven Viaduct (CBC1/34)

Leven Viaduct, which was reconstructed earlier in 2006, is

a 49 span, 460m long structure which carries the

Cumbrian Coast Line over the Leven estuary to the east

of Ulverston. The original structure was completed in

1857 and comprised a series of simply supported riveted

girder decks, with span lengths typically of the order of 

8.5m to 9.5m. The structure was originally supported on

cast iron trestle piers but these were subsequently

encased in brick faced mass concrete. The permanent

way over the structure comprised jointed rails on

longitudinal timbers. As part of the Form B design

process outline schemes were prepared based on both

reinstatement of the longitudinal timbers and the adoption

of CWR on Pandrol Vipa baseplates. In order to

determine whether the latter was viable a track/bridge

interaction analysis was undertaken.

Due to the overall length of the complete structure and the

fact that every connection point between the rail and thestructure had to be modelled this proved to be a

demanding task. Modelling was further complicated by

the need to take account of pier flexibility and the bearing

articulation which permitted a small amount of movement

between the deck and substructure. This introduced a

further degree of non-linearity to the modelling process.

In addition to determining rail stresses the process was

required to determine the distribution of longitudinal forces

between the intermediate piers, abutment bearings and

rail under braking and traction.

 As certain assumptions had to be made regarding pier and abutment stiffness and the degree of bearing fixity at

span 37 (which was the only element of the original

structure to be retained), sensitivity analyses had to be

undertaken to ensure that the most onerous effects were

identified for the critical locations. This requirement,

combined with the large number of load cases that had to

be considered resulted in approximately 150 separate

analyses having to be undertaken. These analyses

demonstrated that CWR could be adopted across the

bridge.

Final Remarks

• Direct track fixing systems offer a more sustainable and

maintainable track support system than longitudinal

timbers

• Track/Bridge interaction analysis is a time consuming

process. Clearer, deemed to satisfy rules need to be

developed to ensure simple, short span structures with

direct fixing can be adopted without recourse to expensive

analysis

• On complex structures, sufficient sensitivity analysis

needs to be undertaken to ensure that critical conditions

have been identified for all elements

Paper 7Track/Bridge Interaction and Direct Track Fixing

Figure 4 - Pandrol Vipa Baseplates fixed to support stools

Figure 5 - Completed track on the up line deck

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65Railway Bridges - Today and Tomorrow

Paper Eight

Soil/structure Interaction and Railway

Bridge Structures

N.J. O'Riordan and O.J. Riches

OVE ARUP

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 Appropriate analysis of the railway bridge structures can

achieve significant economies in both rail upgrade and

new-build situations. For example, coupled analyses of 

existing bridges and their foundations under the various

load cases for upgraded lines can provide reliable

predictions of performance in service that minimise the

need for new or strengthened foundations. Similarly,

recent advances in the understanding of the soil/structure

behaviour of integral bridge abutments enableeconomies to be made in the construction of new,

bearing-free bridges. Examples of soil-structure

interaction analyses in these situations are provided and

the associated requirements of ground investigations and

analytical techniques are described.

1.0 Introduction

The process of design and analysis of railway bridge

structures and their foundations is often simplified into

the derivation of a system of forces for a defined series of 

load cases. Foundation design is reduced to theprovision of reactions to that system of forces, and a

check is made to ensure that an adequate reserve of 

safety exists for those reactions, generally using limit-

equilibrium methods. The design is complete. However,

such simplification can lead to uneconomic foundations,

inappropriate structural or ground treatment and, in the

case of integral bridges, unbuildable bridge abutments.

The arrival of new design codes such as Eurocode 7 will

enable closer examination of the serviceability limit state,

to ensure that design is carried out with due recognition

of common bridge design situations which are essentially

displacement, rather than force, controlled.

2.0 Upgrades of existing masonry

bridges

Current trends in increasing line speed result in new

loading conditions for old bridges. These bridges were

constructed either pre-code, or have sustained a range of 

modifications which make assessment difficult today. For

multi-span masonry or hybrid bridges, the way in which

these new loads find their way into the foundation system

can be obscure. For example braking loads are applied

through the rail and sleepers onto the bridge deck, but to

what extent is that load transferred longitudinally into the

comparatively stiff abutment system: can each pier be

considered to act in isolation?

Figure 1 shows the deformed mesh, plotted to anexaggerated scale, from a finite element (PLAXIS)

analysis of a triple span bridge. Bearing replacement was

to be carried out at 3 of the supports; however it was

unclear whether replacement was necessary at the wider 

of the two piers. Simple analyses, whereby the forces

were apportioned according to pier footing stiffness, had

shown that the foundation could become overstressed

under the new loadings. As a result, underpinning of the

footing at the widest pier was considered.

 At the wider pier, a number of support conditions were

considered, the most extreme being that the deck/pier connection could fail in tension, thereby transferring

braking forces onto adjacent supports through the

bearings. The analysis explicitly included material

properties for ballast, deck, masonry and bearings, as

well as the founding soils. The soils were carefully

investigated and were found to be locally stiffer under the

footings, as a result of long term loading over the lifetime

of the structure. The analyses included this variation in

soil stiffness.

 As a result, it was found that the adjacent supports were

sufficiently stiff to keep displacements of the rail, deck

and footings to within acceptable values, without the

need for treatment of ground or deck connection at the

wider pier location.

66

Paper 8Soil/structure interaction and railway bridge structur es

Railway Bridges - Today and Tomorrow

Figure 1 - Finite element analysis of 3 span bridge under combined train breaking and acceleration on adjacent tracks

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3.0 Dynamic analysis of bridge structures

The analysis described above was carried out using

quasi-static loads, with no allowance for the generally

beneficial effects of inertia and damping. Sometimesrecourse to full dynamic analysis of bridges under train

loading can also result in substantial savings.

O'Riordan et al (2003) and Montens et al (2003)

presented the results of dynamic analyses of piled slab in

which the performance of piles under vertical cyclic load

testing was combined with service loadings from Eurostar 

and heavy freight trains for the design of the Channel

Tunnel Rail Link over an 11km length of high speed line

across the West Thames marshes. Pile stiffnesses were

derived from vertical and horizontal cyclic load tests on

individual prototype piles. Theeffect on pile response to the

rotational stiffness at the pile/slab connections was also

examined in the pile load testing. Figure 2 shows a typical

slab arrangement in cross-section and Figure 3 shows the

output from an LS DYNA 3D finite element analysis. Thetrain suspension system and rolling axles were fully

modelled, as were the piles. Straightforward application of 

design standard UIC 719-R would have resulted in a

cyclic characteristic force of 560 kN/pile. Results from

dynamic analysis showed a maximum of 340 kN/pile

under passing trains, concentrated in those piles at the

ends of each 60 to 120m length of slab.

In this case, soil-structure interaction analysis enabled the

pile and slab design to be optimised, providing a more

economical solution than the straightforward application

of the design standard.

67

Paper 8 Soil/structure interaction and railway bridge structures

Railway Bridges - Today and Tomorrow

Figure 2 - Illustrative cross-section of piled slab supporting ballasted track, after Montens et al, 2003

Figure 3 - Time history ou tput from dynamic analysis,

single heavy freight train at 95 km/hr 

CROSS SECTION

60m slab - 4 pile groups - HFT 98kmh

   A  x   i  a   l   f  o  r  c  e

   i  n

  p   i   l  e

   (   k   N   )

Time (s)

 Axial force - beam 402251 - Pile 1 Flow 13

Oasys T/HISVersion 8.2

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4.0 Soil-structure interaction for integral

bridges wi th embedded abutments

In order to avoid the costs of maintenance and repair to

movement joints in bridge decks, there is increasing use

of integral bridges for road and rail (Hambly,1997). In the

UK, the Highways Agency position is that all bridge decks

up to 60m in length and with skews not exceeding 30

degrees are generally required to be continuous. Figure 4

illustrates such a bridge. Resistance to longitudinal

thermal and braking forces is in consequence provided

directly by the soil at the abutments and at any

intermediate support. The way in which the soil at the

abutments resists these repetitive, transient forces has

been the subject of theoretical and laboratory-scale

studies in the UK, for example Springman et al (1996),

England et al (2000), Xu et al (2003) and Cosgrove and

Lehane (2001). All studies show that soil resistance

increases with numbers of cycles of repetitive movement

of the abutment. The soil resistance is controlled by the

magnitude of the movement and/or rotation which arise

from the imposition of deck forces on the abutment. Some

full-size abutments have been instrumented with

inclinometers, thermistors and pressure cells and theassociated measurements have been reported by Darley

et al (1998) and Barker and Carder (2001, 2006).

Current design guidance follows two separate

approaches:

i) the application of specified distribution of lateral soil

pressures which varies with type of abutment (HA,

2003), referred to as the 'K* method', and which

resembles a limit-equilibrium design method, or;

ii) soil-structure interaction analysis using constitutivesoil models of varying complexity

The K* method is implicitly limited to situations where

abutments retain normally consolidated soil, and is widely

regarded as over-conservative, especially for embedded

abutments (see for example Muir-Wood, 2001). The

second approach can be applied to any situation,

provided that the stress history and stiffness of the soil at

the abutment is properly modelled. We find that, where

measurements exist, the soil pressures can be

adequately described using a single monotonic push

arising from the thermal expansion of the bridge deck.

This considerably simplifies soil structure interaction

analysis, but nevertheless provides the opportunity for 

economic design. Figure 5 shows apparatus developed

by England et al (2000), and Figure 6 shows the results of

68

Paper 8Soil/structure interaction and railway bridge structur es

Railway Bridges - Today and Tomorrow

Figure 4 - Construction of an integral highway bridge with embedded wall abutments

Figure 5 - Apparatus for measurement of soil pressures

acting on a rigid retaining wall sub jected to repetitive

cyclic loading,(after England et al, 2000)

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simulations using the retaining wall programme FREW

(Pappin et al, 1986).

The horizontal soil stiffnesses implied by the best-fit

curves in Figure 6 are about 4 or 5 times higher than

would be expected for soil undergoing a single application

of load. The total (i.e. double-) amplitude of movement in

the test reproduced in Figure 6 is 0.25%, equivalent to a

thermal cyclic movement of 125mm for a 5m high

abutment that is free to rotate at the base.

Integral Bridge Analysis

The analysis of integral bridges is complicated by the high

degree of redundancy of these structures, the associated

induced load effects (e.g. temperature loading, creep and

shrinkage) and the global response of the whole bridge tolocally applied loads. As the soil response to bridge

movements is essentially non-linear, care needs to be taken

to establish the critical (extreme) soil responses and to

conservatively combine these with the appropriate load

effects. A single 3-dimensional grillage model, representing

the entire bridge and foundation is required, to analyse,

combine and envelope the large number of different loads

applied to the bridge.

The analysis procedure shown in Figure 7 allows critical soil

responses to be identified in FREW, by applying the

constrained forces and moments derived from a grillagemodel of the deck (the connection to the abutment is

modelled as encastre) directly to a FREW model where the

axial and rotational stiffness of the deck have been

modelled. This soil response can then be simply converted

to a soil pressure (for the more highly loaded soil zones) and

soil spring values (where the soil response is well within the

elastic range) to be applied to a GSA model. The analysis

results for the combined load effects in the grillage model

correlate closely to those achieved in the FREW model.

In addition the time dependent effect of repeated soil loading

can also be modelled in FREW as described above and

demonstrated in Figure 6, and thus the soil response tothermal expansion after repeated loading cycles can be

identified.

69

Paper 8 Soil/structure interaction and railway bridge structures

Railway Bridges - Today and Tomorrow

Figure 6 - Results of FREW analyses of Test SW25 of England

et al (2000), geometry upscaled 10 times. Measured values

are shown dashed. Solid lines are pressures obtained using

the quoted horizontal Young's modulus values.

Figure 7 - Analysis Procedure for Soil/Structure Interaction of Integral Bridges

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Comparison of Limit Equilibrium and Soil/Structure

Interaction Analysis Methods

The following exercise was carried out for the Highways

 Agency, to demonstrate the effectiveness of simple soil

structure interaction methods and to allow a direct

comparison to be made between limit equilibrium

methods and soil structure interaction methods for integral

bridge analysis. This is part of on going research to

support the development of a new design standard for 

integral bridges.

The effect of different soil loading approaches was

investigated on a 35m span integral portal bridge withembedded abutments (see Figure 8). The design of this

form of structure, which provides a low maintenance

structure that allows the deck to be quickly erected in

short road closures/railway possessions is documented

elsewhere (Riches et al, 2005).

Limit Equilibrium Approach

Earth pressure distribution was calculated in accordance

with standard limit equilibrium theory (i.e. ka and ko to BS

8002) with vehicle surcharges applied as a constant

pressure behind the abutment.

These loads were applied directly to the three dimensional

grillage model in accordance with proposed rules to be

included in a new Bridge Design code on integral bridge

designs, whereby a pressures are applied over a defined

zone as indicated in Figure 9. Below this point the soil

response was obtained by applying elastic soil springs.

In accordance with BD 37/01, 4 critical soil responses

were identified:

Group 1 min ko

Group 1 max ko + vehicle surchargeGroup 3 min ka

Group 3 max k*

Soil Structure Interaction

The soil pressures and elastic soil spring values were

obtained from a FREW analysis by applying deck

restrained forces and moments (obtained from a 2D

grillage model of the deck with encastre ends) from the

following load cases to identify the soil response:

Group 1 min Dead load hogging moment

Group 1 max Maximum deck hogging moment +

vehicle surcharge applied to soil

Group 3 min Thermal contraction + dead load only

hogging moment.

Group 3 max Thermal expansion + maximum deck

hogging moment (soil properties modified to model long

term soil response)

In order to model the long term soil response in FREW soil

stiffnesses were obtained using 'small strain' soil

stiffnesses, for example those values published by Seed

70 Railway Bridges - Today and Tomorrow

Figure 8 - Bridge geometry and structural form

Figure 9 - Soil pressure distribution using the limit equilibrium

approach

Paper 8Soil/structure interaction and railway bridge structur es

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and Idriss (1970) applicable to a shear strain level of 10-

6. Other formulations are available, for example in Lehane

et al (1996), and these lead to similar, very high, values of 

horizontal soil stiffness for the repetitive load effect under 

thermal cycling of the bridge deck.

For both approaches, the loads were applied to a grillage

model and factored, combined and enveloped to generate

an ULS envelope of load effects. A comparison of the two

approaches was then carried out, and a summary of our 

findings is presented in Table 1 below.

This exercise demonstrates the limitations of the simpleapplications of limit-state theory soil pressures to such

structures. Simple limit state theory cannot accurately

define the distribution of soil pressures which are

generated as a direct response to abutment movement

caused by deck loading. The use of a soil/structure

approach to identifying critical soil pressures should lead

to significant cost savings in abutment reinforcement and

piling costs and promote the design of new and innovative

bridge forms.

The new bridge design code, currently being

commissioned by the Highways Agency, is likely to

promote the use of soil structure analysis techniques. This

will also encourage the design of such structures for 

railway under-bridges, leading to new, cost effective and

low maintenance bridge forms.

Conclusions

Several uses of soil-structure interaction analyses are

presented. All have enabled more economic design

solutions to be selected, based on careful consideration of 

bridge and soil displacements, and their relationship to

both the serviceability and ultimate limit states. In

particular, the use of soil-structure interaction analyses

will enable the design of integral (bearing-free) bridges tobe optimised, resulting in cost-effective solutions.

 Acknowledgements

The authors acknowledge the support of their colleagues

in Arup, and those clients, which include Network Rail,

Highways Agency, and Union Rail (Northern) Ltd., who

have given us the real project challenges to enable

appropriate solutions to be developed and built.

71Railway Bridges - Today and Tomorrow

Figure 10 - Soil pressure distribution using soil structure

interaction

% Decrease in Load Effect

Negligible

Negligible

Negligible

30%

20%

Deck Sagging Moment

Deck Hogging Moment

Deck Axial Load

 Abutment Moment (tension

on front face)

Pile Moments

Table 1: Reduction in global load effects on an integralbridge achieved by using soil/structu re interaction analysiscompared to limit equili brium soil l oads.

Paper 8 Soil/structure interaction and railway bridge structures

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References

1. Barker KJ and Carder DR (2001, 2006). The long term

monitoring of stresses behind three integral bridge

abutments Technical Paper 10. Concrete Bridge

Development Group.

2. Cosgrove EF, Lehane BM and Ng CWW (2001) Sand

tested under cyclic triaxial conditions with constant radialstress.Proc.Int Conf, Soil Mechanics and Geotechnical

Engineering Vol 1 pp63 to 68.

3. Darley P, Carder DR,and Alderman GH (1994)

Seasonal thermal effects on the shallow abutment of an

integral bridge in Glasgow TRL Reprt 178 Transport

Research Laboratory UK.

4. England GL, Tsang NCM and Bush DI, Integral Bridges

- A fundamental approach to the time - temperature

loading problem, Thomas Telford Limited, 2000.

5. HA (2003)Design Manual for Roads and Bridges,

Volume 1, Section 3, Part 12, BA 42/96 The design of 

integral bridges, Highway Agency

6. Hambly E (1991) Bridge deck behaviour. 2nd edition.

EN Spon.

7. Lehane B, Keogh DL and O'Brien EJ Soil-structure

interaction analysis for integral bridges, in Advances in

Computational Methods for Simulation (ed. BHV

Topping).Civil-Comp Press, Edinburgh pp201-10. 1996

8. Montens S, J-J Leullier, K Benadda and S Jenkins

(2003) Design of piled slabs for the Channel Tunnel Rail

link. Proc. Symp Structures for High Speed Railway

Transportation IABSE Antwerp

9. Muir-Wood D and Nash D (2000) Earth pressures on

an integral bridge abutment: A numerical case study Soils

and Foundations vol. 40, no6, pp. 23-28

10. O'Brien EJ and Keogh DL Bridge Deck Analysis. E

&FN Spon. 1999

11. O'Riordan N. Ross A, Allwright R and Le Kouby A.(2003) Long term settlement of piles under repetitive

loading from trains. Proc. Symp. Structures for high

speed railway transportation. IABSE Antwerp.

12. Pappin JW, Simpson B, Felton PJ and Raison C,

Numerical analysis of flexible retaining walls, Symposium

on computer applications in geotechnical engineering,

The Midland Geotechnical Society, April 1986.

13. Riches O.J., Carstairs N.A., Jones A.E.K (2005),  A

simplified integral composite bridge connection ICE

Proceedings, Bridge Engineering 158 Issue BE2.Seed HB and Idriss IM, Soil moduli and damping factors

for dynamic response analysis, EERC Report No.70-10,

Berkeley CA, 1970.

14. Springman SM, Norrish ARM and Ng CWW, Cyclic

loading of sand behind integral bridge abutments, TRL

Report 146, Transport Research Laboratory, 1996.

15. Xu M, Bloodworth AG, Lee MMK (2003) Numerical

analysis of the embedded abutments of integral bridges. Proc.

Symp. Structures for high speed railway transportation. IABSE Antwerp

72

Paper 8Soil/structure interaction and railway bridge structur es

Railway Bridges - Today and Tomorrow

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73Railway Bridges - Today and Tomorrow

Day Two

23 November 2006

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75Railway Bridges - Today and Tomorrow

Paper Nine

Innovation Now & In The Future

 Alex Cole

FAIRFIELD-MABEY

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76 Railway Bridges - Today and Tomorrow

Network Rail has set a challenge to the industry. It has

identified that it needs to produce significant efficiency savings

that will translate into cost savings year on year. Contractors

and specialist suppliers need to work together to innovate and

deliver these cost savings. Successful teams would be

rewarded with repeat business and the opportunity to

continue innovating. So how can Network Rail make this

happen; how are other clients approaching this problem; what

are the benefits of success; and what are the present barriersthat exist to ensuring that the industry lives up to this

challenge? This paper attempts to answer some of these

questions from a specialist bridge steelwork contractor's

viewpoint.

 As one of the UK's leading bridge steelwork contractors,

Fairfield-Mabey is involved in the fabrication, erection and

protective treatment of around 50 bridges annually. As a

result, we have significant specialist experience of the issues

relating to steel plate procurement, plated steelwork

fabrication, different bridge steelwork erection techniques

(e.g. using heavy cranage, incremental launching or self propelled motorised trailers), and bridge steelwork protective

treatment.

In addition to its specialist experience, the company has

arguably the most automated fabrication facilities in the world

dedicated to bridge steelwork fabrication. These operate 24/7

for 50 weeks of the year and use some of the most advanced

fabrication techniques available to the industry including:

• A fully integrated CADCAM system avoiding the need for 

fabrication drawings on the shop floor and significantly

reducing the effects of human error 

• Computer Numerically Controlled plate profiling, drilling

and marking machines

• Automated plate edge grinding and girder assembly

machines

• Abrand new state of the art robotic welding facility

The combination of significant specialist bridge steelwork

experience and highly automated fabrication facilities is

unique to the company and, as a result, many project

teams like to involve us in developing their designs to help

minimise costs and risks associated with their bridge

steelwork. Many understand that advice is time specific

and that this will change as new technology is introducedto the marketplace, modifying the balance between

different cost components (e.g. if steel material prices

rise). In an attempt to control this process, we collate its

specialist knowledge in a Value Engineering Database,

which we put at the disposal of the teams on the projects

we are involved in.

We are involved in the Value Management process on

many projects for many end users including the Highways

 Agency, County Councils, private developers and

Network Rail.

Each end user currently adopts a different approach to the

procurement of their project and some adopt different

approaches on different projects. Before we look at the

most common approaches and what innovation results, it

is worth considering the different stages of a design and

the points at which cost savings can be made.

The design process typically involves a conceptual design

stage followed by a detailed design phase. At the conceptdefinition stage, stakeholder requirements are analysed

along with client preferences and the concept of the

structure is determined. In the case of bridge steelwork,

this involves choices of materials - concrete, steel, timber 

etc. - and structural configuration - through plate girder,

through box girder, ladder beam, multi girder, bowstring

arch, through truss, cable stayed, etc. It is at this stage

that critical cost related decisions are made and it is at this

stage that specialist input can have the most impact.

Savings of 25% to 35% of structure cost have

successfully been realised on recent projects by involving

us at this concept definition stage. If specialist input is notprovided at concept definition stage, it is not too late to

change structural form later, but the implications in terms

of redesign costs and consequential affect on programme

often make such changes very difficult.

Paper 9Innovation Now & In The Future

Figure 1 - Robot Welding at Chepstow

Figure 2 - Trial Erection of Harthope Viaduct

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77Railway Bridges - Today and Tomorrow

It is important for specialists to give honest advice. For a

steelwork contractor, this means that, if it is clear that a

concrete solution is the best solution for a particular 

problem, we need to say so. In addition, it is important for 

the project team to listen to all of the advice given by the

different specialists, analyse each of the different possible

solutions, and choose the best solution for the project, not

an individual member of the team.

Having chosen a concept, the team can then proceed to

detailed design. For projects involving a steelwork

contractor like ourselves, this includes defining steelwork

details that suit automated fabrication including robotic

welding, that have the right balance of material and

workmanship costs, that suit the chosen erection method,

and that give the client a quality whole life solution in the

quickest possible time and at the lowest possible price.

If the right details are used, cost savings of 5% to 10% can

be delivered by involving a specialist steelwork contractor 

during the detailed design development stages. Again, it isimportant to ensure that the input is provided at the right

time, to avoid any rework and wasted cost and effort from

a design point of view.

The above clearly demonstrates that it is best to involve specialist

suppliers as early as possible in the design development process,and preferably right at the start, before any design work has been

done - effectively when the team is looking at a 'blank sheet of 

paper'. In practise, many end users adopt procurement

techniques that entail the involvement of specialists much later.

The most common and most traditional form of 

procurement is the 'construct only' competitive tender.

In this, the end user commissions a conceptual and

detailed design from a consultant. The consultant may

or may not involve specialists in this work, but the latter are often reluctant to get involved as it is usually more

beneficial to wait until the tender period and then take

advantage of one's specialist knowledge to help win the

work. Having picked a contractor, the end user then

expects 'value engineering' initiatives to deliver 

savings. These initiatives can work, but their success is

often restricted by programme and savings are often

outweighed by the time, cost and risk associated with

the redesign. For bridge steelwork, this process is

unlikely to involve changing the structural design

concept and therefore the most it will deliver in terms of 

savings is 5% to 10% of structure cost, assuming of course that the value of the savings are the full value

and the specialist does not ask for a share. We do not

have a problem with this form of procurement. In fact,

with a market share approaching 75%, Fairfield-Mabey

likes such projects as they are often a good source of 

additional profits. The company looks for a share of the

savings it generates, making this form of procurement

a theoretical 'win-win' situation for all involved. The

traditional 'construct only' competitive tender does not,

however, produce the largest possible savings for end

users such as Network Rail as many of the possible

savings do not materialise because of the associated

implications on programme and additional design work,and because they are only getting a share of the

savings from the small number of changes that are

adopted.

The next logical step in procurement route is 'Design

and Build'. Here, the end user invites tenders on a

Design and Build basis. Contractors then employ a

designer to produce as much design as they need to

provide accuracy of price. At this stage, however, the

contractor's spend is at risk and he wants to spend as

little money as possible before he is awarded the

project. Some team up with specialists such asFairfield-Mabey to help with this process, and the result

can be a low cost design concept. Many do not,

however, and again the design ends up very similar to

Paper 9 Innovation Now & In The Future

Figure 3 - Erection of Leven Viaduct

Figure 4 - Leven Viaduct

Figure 5 - Baswich Fastlines Viaduct

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78 Railway Bridges - Today and Tomorrow

that which is produced via the 'construct only' competitive

tender process, but lacking in detail. Then, a big risk

comes into play, the 'design growth' risk. How much will

the design that the specialist has priced change by before

he builds the bridge? This risk is very difficult to price, and

many contractors have lost money as a result of getting it

wrong. The inevitable result is that risk allowances grow

and any savings generated by getting specialists involved

go to mitigating the effects of post award design growth,or increasing the contractor's and specialist's possible

gain. Again, we are more than happy to get involved in

such projects and have successfully made money on

many of them. They do not always, however, provide the

best result for the end user like Network Rail. This is

because any savings that are generated by getting

specialists involved during the tender process are usually

counteracted by the risk allowance for future design

growth, whilst any savings generated post award only

serve to increase the contractor's and specialist's return

from the project.

The most modern form of procurement technique has

commonly become known as 'Early Contractor 

Involvement' (ECI). In this, the contractor is employed

under a professional services agreement to work up a

design and associated target price. In the event that the

target price goes over budget, the end user can choose

not to proceed or, in exceptional circumstances, to put the

project out to competitive tender. Contractors can getspecialists involved at the right stage - the concept

definition stage. The largest project savings can thus be

made and, because the contractor and specialists are

involved in developing the design, construction method is

taken into account, and programmes become more

realistic. Price competitiveness is demonstrated via an

'open-book' arrangement and by benchmarking against

other competitively tendered projects. If the process

works well, the end user gets all of the benefit from the

involvement of the contractor and his team of specialists.

The contractor and specialists get a fair return and it is a

true 'win-win' situation for all.

With repeated use of the ECI procurement route involving

the same project teams, continuous improvement can be

bought to the fore, with team members taking what has

been learnt from project to project and improving on it

each time. As each project is completed, trust develops

and traditional contractual relationships are broken down

to the benefit of future projects.

We are involved in a large number of ECI schemes for many clients. We have seen many successes, and some

failures. The most important ingredient to this form of 

procurement route is trust between the parties. It is often

when this breaks down that the process fails to deliver 

Best Value to the client. It is without a doubt the most

difficult procurement route to administer and get right, but

when it works, it can deliver significant savings to the end

user.

The main benefit to specialists from such a form of 

procurement is long-term visibility of workload and the

assurance that the work will be carried out in a nonadversarial partnering environment.

Certainty of future workload would enable specialists to

plan better for the future, to continue to invest in new

technology, and to continue to deliver better value to their 

customers.

End users such as Network Rail can benefit significantly

from the ECI procurement route. This would be one way

of generating the efficiency and cost savings it is looking

to achieve. Its ECI project teams could then be involved in

driving the industry forward, reviewing and updating

specifications and developing new standard designs for 

its infrastructure. This would not involve simply tweaking

existing designs. To get real savings, design codes and

other criteria need to be challenged and developed for the

good of all.

The most important ingredient to making the ECI process

work is trust between the parties. Without this, it is

doomed to failure. Our industry is full of people who do not

trust each other.

Paper 9Innovation Now & In The Future

Figure 7 - Channel Tunnel Rail Link - 22 Bridges

Figure 6 - Gelderd Road Bridges, Leeds R & R

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79Railway Bridges - Today and Tomorrow

When a specialist steelwork contractor suggests that a

project team should design a bridge to suit its automated

facilities, or involve him early in the design process, he

gets mixed responses. Some, who have not worked in this

way before, assume that all the specialist is trying to do is

gain an advantage over his competitors. They suggest

that he will take advantage of the situation by inflating his

prices and making exorbitant returns. Others, who have

seen the benefits on past projects, would often like for it to

happen, but are constrained by policies that dictate that all

contracts should be competitively tendered.

Clearly, the responsibility rests with the specialist to

convince project teams that he can help deliver better 

value through early involvement and that he can be

trusted not to take advantage of the situation. It is also

clear, however, that a team approach and a willingness to

adopt a modern approach to procurement such as ECI,

would enable specialists help deliver the cost and

efficiency savings that Network Rail is looking to achieve.

Figure 8 - Erection of River Tame Bridges, TV4

Paper 9 Innovation Now & In The Future

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81Railway Bridges - Today and Tomorrow

Paper Ten

Design for Minimum Future Management

/Maintenance Costs

Tim Holmes and Dr. Paul Jackson

GIFFORD

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Introduction

One of the most prevalent complaints of civil engineers

over the last twenty to thirty years has been the apparent

lack of foresight in considering the future needs of road

and rail transport on the development of new

infrastructure, and the lack of consideration when

refurbishing the existing network of future operational

service requirements.

The authors have been involved in many projects where

the 'Brief' is solely concerned with solving the present

situation with no recourse to considering whether the

preferred option will facilitate further expansion. A very

pointed example in the late 1970s was a new motorway

contract which was originally designed as three lane and

then for cost reasons re-designed as two lane with no

accommodation for future widening. Widening is now

taking place with major issues concerning land take,

bridge replacement/widening and all the other associated

issues of disruption, service undertaker diversions andeffects on other adjoining infrastructure. All of these had

been major problems the first time around.

Even now, on major upgrading schemes, there appears to

be still no apparent consideration to potential future

modification needs and, even worse, no actions are taken

with respect to potential future management issues

associated with the continued re-use of the modified

infrastructure. There appears to be a view that 'Design'

and 'Future Management' of the Infrastructure are totally

distinct areas. Indeed, until quite recently, the

organisational set up within many private engineeringpractices and public engineering departments reflected

this view.

For a Bridge, 'Future Management' embraces a number of 

major issues reflecting its continued 'Functionality', i.e.

how can it continue to meet the 'Operational' requirements

of the road or rail network. It is considered that these key

issues include future steady state maintenance, renewal

and upgrade of components, future modification or 

demolition and replacement and ability to remain 'fit for 

purpose' when subject to events such as fire, impact and

flood. 'Functionality' should also include provision for 

inspection and repair, renewal and supply of futureservices, re-gauging and even protection from graffiti and

pigeon roosting.

Maintenance is a key issue and in the last twenty years

great strides have been made in the understanding of the

various modes of degradation of structures and in the

development of robust specifications for various bridge

components. However, there is still a lack of 

consideration of 'maintenance' in Design, particularly with

respect of adopting 'Best practice' solutions and providing

the necessary access for undertaking maintenance and

the future replacement of components or indeed givingthought to 'over-design' in certain critical areas.

It is the Authors' considered opinion that there is need in

'Design' for an 'Operational Limit State' that reflects the

'Future Management' needs of the structure.

In giving consideration to this additional 'Limit State', it is

recognised that 'Cost' must still be a major issue in the

development of any proposed scheme. To date, 'Future

Management' Issues have to a large degree been ignored

given the discount rate mechanism used in any 'WholeLife Costing' comparison that has been undertaken. Also,

there has been a lack of political will for spending now to

facilitate the future 'Operational Needs' of structures.

This paper gives some thoughts on the content of an

'Operational Limit State' and also on the methods that

should be adopted in determining the appropriate way

forward for a particular Rail bridge scheme. This can be

termed 'Design for Minimum Management/Maintenance

Costs'.

 Aspects of Funct ional ity

This 'Functionality' can be separated under a number of 

different headings:

• Maintenance

• Modification/Replacement

• Rail Operations

• Exceptional Events

• Secondary Components

• Third Party Issues

a) Maintenance

This should embrace:

i. The use of standard detailing promoting Best Practice

- this is already well underway within Network Rail for 

steel footbridges and this is to be extended to rail

underbridges. This is a great step forward that promotes

both buildability (another key issue of design) and also

'state of the art' structural steelwork detailing that gives

proper emphasis to future maintenance by the provision

of suitable components, connections and a robust

protection specification.

ii. Designing out of Maintenance Issues - consideration

must be given to the elimination of potential critical areas

for corrosion or where access is difficult.

 As an example, Integral bridges are favoured by the

Highways Agency as they eliminate joints and bearings.

Consideration should be given to their use but they can

also have their disadvantages. For instance, their 

design can be complex and their use for upgrading

existing structures may necessitate modifications to the

substructures. They also preclude the future jacking of 

the structure which could be a major problem if, for instance, re-gauging could be a potential functional

requirement for the bridge.

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'Over-design' of critical components should be

considered; this is often a very cost effective way of 

introducing further life into the structure. This is very

common practice on marine structures for very good

reason and could easily be adopted for bridges.

iii. Form and Material Type - more emphasis should be

given on the choice of form and material type to minimise

future maintenance issues. It is recognised that the formand material type are dictated to a large degree by

issues of geometry, loading criteria, ground conditions,

etc but it is felt that more consideration should be given

to evaluating the maintenance issues that could arise

from each potential solution. The ongoing debate of the

use of GRP versus concrete and steel solutions should

be evaluated.

iv. Specific Maintenance Issues - it is important to

recognise that for particular structures, their functionality

is directly related to their condition. This can be, for 

example, maintaining the protection works for potentialscour to river and marine works. It is also an extremely

important matter for structures such as underpasses for 

pedestrians where their safe use is related to issues of 

drainage, vandalism, graffiti, lighting, etc.. These should

be critical elements of the 'Design', especially as

'maintenance' will probably be a regular occurrence.

The effects of pigeon roosting can both be an

environmental issue and also lead to potential

maintenance problems for the structure. Again, the

Design must reflect this.

v. Access - Future access for inspection and

maintenance needs to be an integrated part of the

Design and must give due consideration to rail

operational matters. Where the cost of conventional

external access is high, either in terms of direct or 

disruption cost, further thought should be given to

designing it out. For instance, the Highways Agency

uses Inspection Galleries for access to bearing

shelves/end of beams/drainage.

From an inspection perspective, it is important that a

General Inspection can report visually on all key

components. It is considered that reliance on the

Principal Inspection, possibly with difficult access issues,is inappropriate for monitoring ongoing maintenance

issues.

b) Modification/Replacement

It is considered that much more emphasis needs to be

taken during the development of options to potential

modifications that may need to be undertaken to maintain

the functionality of the structure during its potential 120

years life. It is recognised that many of the replacement

structures over the next five to ten years will be in areas

of the network where there will be major logistical issues.For these especially, consideration of future modification

could be considered to be a key requisite of the design.

Modification may not take place but to design simple

practical methods does not need to be a costly matter.

For instance, for potential widening of a structure, the

Design could explore the over-design of particular 

components, facility for the removal of the edge members

and the introduction of couplers buried in the structure.

There is a general need to think much more in Design

about the use of 'modular systems' for easy erection and

removal.

More thought also needs to be given to substructures interms of potential upgrade/modification. Presently, major 

issues are being experienced on the upgrade of quite

recent substructures on road and rail schemes where all

the information is not available covering issues such as

backfill properties, pile capacities, chemical testing

results, etc.. Even where the information is available,

there is a lack of reserve capacity for 

upgrading/modification without major recourse to further 

site investigation and strengthening. On the older stock of 

structures, every bridge deck reconstruction raises issues

of abutment stabilisation during the works and of potential

dead or live load increases. For new structures or major upgrades, it would not be expensive to provide a reserve

of capacity to cater for a potential future modification of 

the structure. This could include allowing for temporary

stability during any deck re-construction.

c) Rail Operations

For a rail structure, it is imperative that its future

functionality addresses the needs of the 21st Century

railway and beyond! To this end there are key issues

associated with matters such as:

• Potential Upgrading for Gauging clearances, in particular 

headroom

• Track re-alignment

• Power/signal implications, e.g. fixings for OHLE masts

• Provision of Access/Safe walking routes, etc.

• Communication cables, drainage, etc.

Obviously, Technical Approval does include the short term

inter-disciplinary issues but more strategic thinking shouldbe undertaken. For instance, future implications of re-

gauging for freight could necessitate lowering of the tracks

or raising the structure on an overbridge. Potential for 

 jacking the structure or deepening the foundations could

be appropriate.

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d) Exceptional Events

Bridge strikes are a major issue with rail underbridges,

especially as headroom cannot readily be increased.

Even with impact design, there is still a major risk of 

damage to the edge girders and of movement of the

structure. Independent barriers have been used on some

bridges which, although preventing damage to the bridge,

can cause safety issues with the itinerant vehicle andother road users. The use of crash cushions or other 

forms of sacrificial component that act like a crumple zone

to dissipate the energy from the impact, should be

considered as a possible way forward.

Design for functionality should also consider the

implications of vandalism, fire, flood and the like.

e) Secondary Components

 Although robust Specificat ions exist for all bridge

components, such as joints, bearings, and waterproofing,it is imperative that the Design includes the choice of 

appropriate proprietary products. These should meet the

structural needs of the bridge and be able to be

maintained in a suitable manner to meet their predicted

service life.

The Design must also recognise that Secondary

Components will need to be replaced from time to time.

Therefore they should be easily replaceable without

compromising the structural performance of the structure

and without progressive dismantling of adjacent elements.

The Design also needs to assess the need for temporary

works and access required for replacement including

implications for traffic closures.

For bearing replacement, it is essential that provision is

made for jacking, such as the incorporation of additional

stiffeners and jacking plates, so that this can be carried

out with least disruption.

f) Third Party Issues

In assessing the continued functionality of a structure, it is

important to consider the future 'Operational' needs of 

Third Parties affected by the bridge. For a rail bridge, thiscan obviously include a Highway Authority, Statutory

Undertakers, Local Developers, etc. A number of issues

can arise which the Design should attempt to address.

These include:

• For an overbridge, Statutory Undertakers apparatus

can have a major effect on the form of construction and

on providing suitable access for their maintenance and

possible replacement. They can have significant

implications for the water tightness of the structure. It is

therefore essential to realise the need to develop

appropriate details around the services including, wherenecessary, allowance for relative movement between the

services and the structure, and which at the same time

protects the structure from ingress of water 

The Design must also consider the effects on the

structure of future maintenance and replacement of the

services and also the replacement of secondary

components associated with the services. For 

underbridges, access to services beneath the structure

may have implications on stability of the structure and

this should be considered during the Design.

• Provision of additional ducting for future additional

services should be considered during the Design.

Experience has shown this to be a sensible approach to

avoid potential modifications to the bridge at a later date

• The Design must also reflect the maintenance needs

for the Highway Authority associated with areas such as

lighting, drainage, highway improvements and the like

The Way Forward

The above has discussed what should be considered indesign beyond the immediate issues of strength and

serviceability. It remains to consider how this might be

encouraged within existing Contractual Arrangements.

This can be particularly difficult when Contracts are let on

a Design and Build basis. The idea is that tenderers

should compete to achieve the minimum price within a set

of defined criteria. It is therefore desirable to include all

the issues considered above within the criteria.

Ideally, many of these issues would be considered

quantitatively as an additional limit state which might be

called the "operational limit state".

There is a gradual move towards such quantitative design

and the concept of a limit state of durability has been

raised. In principle the life could be calculated and

checked against the required design life just as other 

limits are checked.

In practice many of the issues considered cannot be

analysed in this way, or perhaps cannot yet be analysed

in this way. Durability itself has not reached this point

although modern design codes such as EN 1992 are

moving in that direction.

 Another alternative is to incorporate what is required in

the Specification or other documents. The Highways

 Agency has moved a long way in this direction with

numerous documents defining what is required. One of 

the most significant is Design for Durability, the document

which promoted the move to integral bridges.

Specifications also define such components as

waterproofing.

 A disadvantage of this approach is that it is prescriptive

and could stifle innovation. There is a move towards

performance specifications but it is difficult to measuremany aspects of performance. For example, use of epoxy

coated or stainless steel reinforcement, which are not

normally used in standard UK specifications, may give as

84

Paper 10Design or Future Minimum Management / Maintenance Costs

Railway Bridges - Today and Tomorrow

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good a durability performance with other aspects of 

current specifications relaxed, e.g. cover, concrete quality

or the requirement for waterproofing. However, this is not

easy to prove.

Some of the issues effectively have to be considered by

the client side, and cannot be incorporated in a Design

and Build Contract. A design and build contractor cannot,

for example, decide what provision for future increases incapacity are needed. It may, however, still be useful to

quantify such issues.

One potentially useful approach is a 'Risk Evaluation'

Register which can act as an audit trail for determining

which issues as detailed above should be included for in

the Design of a particular structure. It is recognised that

cost will always be a major factor in some of the decision

making BUT it is considered that many matters are key to

the future functionality of the structure and must be

reviewed in detail.

In addition to more obvious "risks" such as of accidents,

probabilities of major increases in services requirements

or traffic increases could be considered. The potential

cost saving by providing for these in advance could then

be evaluated. Although the estimated probabilities are

unlikely to be accurate, they will give some indication of 

whether such provision is viable.

Closing Remarks

Many of the issues raised here are no doubt being taken

into account. However, there is much scope for improving

the consideration of long term management of structures

in design, and the ways in which these might be

encouraged have been proposed.

85Railway Bridges - Today and Tomorrow

Paper 10 Design or Future Minimum Management / Maintenance Costs

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86 Railway Bridges - Today and Tomorrow

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87Railway Bridges - Today and Tomorrow

Paper Eleven

 Advances in Rail Underbridge

Replacements

 Andrew Dugdale

HYDER CONSULTING (UK)

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88 Railway Bridges - Today and Tomorrow

 Abstract

U-Decks, or 'Bathtubs', are a recent introduction to the UK

rail infrastructure, the benefits being in simplified

fabrication, improved appearance and reduced

construction depth. The 13m span structure in Darlington

was replaced during the weekend of 27-30 August 2004

using two identical U-Decks. The paper reviews the

construction 4 bridge deck replacements (including oneU-deck) and comments upon the constraints leading 4

very different solutions

The paper describes the benefits of the U-deck deck,

reviews the main structural aspects and compares the

design with more traditional U-frame steel rail underbridge

solutions. The paper reviews construction depths for 

several types of deck including ballasted and fixed tracks.

The U-deck is constructed by welding the girder webs

directly to the single deck plate. The deck is in filled with

concrete and provides a fully tanked bridge deck for waterproofing. The composite action of the concrete infill

enabled the construction depth to be minimised to

220mm, compared to 250mm for a standard battle deck.

This saving in construction depth facilitated the provision

of ballasted track, whilst maintaining the existing

headroom and avoiding the need for a track lift.

The off-site fabrication of the steelwork and in situ

concrete enabled the decks to be craned into position

during a single weekend possession. A review of 

construction techniques (Crane v Heavy duty transporter)

is also included, together with discussions on buildability.

Keywords: Rail Bridge, U-Deck, Steel, Construction

Depth.

1.0 Introduction

In 2004 the British Government introduced a White Paper 

entitled 'The Future of Rail' [4] which updates the 10 year 

plan presented by the SRA as a vision of the rail network

in 2010. The original vision for increasing the nation's rail

passenger capacity by 50% has now been moderated to

35%. Since publishing the initial plan it has been

identified that much of the UK rail network is running closeto capacity, with capacity of main lines often dictated by

discreet bottlenecks. Moreover, the desire to increase

freight traffic by 20% is at odds with running an efficient

high speed passenger service on the same tracks.

Throughout the current London North Eastern (LNE) territory,

secondary routes have been identified for upgrading to

primary freight routes, thereby opening up the East Coast

Main Line (ECML) for an increased volume of high speed

passenger trains. These secondary routes contained many

of Britain's 40,000 railway bridges and tunnels [17] which

require ongoing inspection and maintenance, the majority of 

which span local roads and are in the span range of 10 to

20m.

Many of these structures date back to the original

construction of the railways, in times when road traffic was far 

less than today and headroom restrictions were considered

acceptable. As a result, the current rail network includes a

significant proportion of rail underbridges with a clearance

less than 5.3m as currently required by the Highways Agency

document TD27/96 [8]. In recent years the number of bridge

strikes reported to Network Rail has shown a steady increase.

Between April 2003 and March 2004 there were 1870 bridge

strikes at railway bridges over a road reported to Network Rail

[13]. The demands on bridges on the modern rail network are:

• Increased line speed

• Increased capacity to Route Availability (RA)10

• Design Life of 120 years

• Headroom clearance to be maintained or improved

Since 2000 Hyder Consulting have been working with May

Gurney Rail under their Structures Partnership with Network

Rail to assess the feasibility for strengthening and

replacement of bridge decks. This paper reviews four recent

replacements with particular emphasis on the modern U-

Deck design. The structures reviewed are:

• Neasham Road (DSN1/2): Twin U-deck installed by

crane. The steel deck with composite concrete floor was

chosen in conjunction with the desire for ballasted track for 

its minimal construction depth

• Ridley Hall (NEC2/96): Reinforced concrete slab

incorporating Edilon direct fixing installed by HDT

• Forge Road (NEC1/20): Twin girder with transverse

battle deck installed by HDT. Twin ballasted track was

provided with shallow depth concrete sleepers

• Sand Lane (ABE1/7): Twin 'Z' girder half through type

with steel battle deck type floor units installed by crane.

Ballasted track was provided on steel sleepers with a

tracklift of 125mm

Paper 11 Advances in Rail Under bridge Rep lacements

Figure 1 - Neasham Road Underbridge (Cantilever footway and concrete deck in fill omitted)

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89

Paper 11

Railway Bridges - Today and Tomorrow

2.0 Design Constraints

2.1 Possession availability

 A distinctive feature of bridge replacements in the modern

railway environment is the requirement to be installed and

commissioned within possessions; typically the rails and

ballast are removed, the deck replaced and the track re-

opened within a 54 hour period. Often these possessionstake place on bank holidays and their very nature

necessitates 24 hour working. This high pressure

environment creates risks of its own which must be

managed by the Contractor. The designer role, reinforced

by the Construction (Design and Management)

Regulations [9], is to ensure that all risks are 'designed

out' as far as reasonably practicable. This is best

achieved through early consultation with the Contractor 

during the feasibility stage.

Throughout the design and construction process May

Gurney and Hyder convened regular workshops involving

the designer and construction teams. It was found

advantageous to include hold points on the design until

reviews were complete to ensure that previous lessons

were incorporated and time-consuming site operations

were avoided during the possession period.

Understanding the risks to the programme during the

possession period were key to delivering successful

designs, ensuring installation and track hand-back within

the permitted timescale. Often off-site fabrication wasrequired, with bridge deck components erected close to

the bridge site; this acted both as a trial erection and

allowed components, too large to be transported by road,

to be erected. Wherever possible possession activities

were reduced to an absolute minimum, with consideration

for adverse weather conditions taken into account.

2.2 Geotechnical Considerations and Exist ing

 Abutments

During the early stages of the feasibility design it was vital

that the designer undertook an adequate site investigationto determine ground conditions and the condition of the

existing abutments. Significant savings in both time and

money were achieved by retaining the existing abutments.

 Appendix C of GC/RC5510[12] gives guidance on the

assessment of existing abutments for re-use.

Ground conditions were established through the use of 

trial holes and dynamic probes, while the condition of the

abutments was obtained through structural inspections

and coring to determine thickness and depth of the

foundations. Where record drawings were available they

were verified by coring, otherwise typically up to 10 coresin each abutment were required.

Where existing abutments were retained, the construction

depth and requirement for access to bearings for 

inspection and replacement usually meant that the cill

beam level needed to be reduced. It was found that this

was best achieved by removing the existing beams or 

stonework to a reduced level, providing a level bed of in-

situ concrete (usually lean mix) and providing new

reinforced concrete cill beam units; braking forces can be

resisted by doweling into the retained abutment if 

required. The size and number of the units will begoverned by installation techniques and weight limitations.

2.3 Environmental Issues

Environmental issues are increasingly important and need

to be reviewed at the feasibility stage. An environmental

checklist was prepared in accordance with

RT/LS/P/007[14] to satisfy the client's requirements and

included in the Environmental Management Plan. Liaison

with the Local Authorities, Environment, English Nature

and local groups highlighted the presence of protected

flora, fauna or wildlife, in particular bats often use the

existing bridge soffits as roosts. Trees in the vicinity of the

bridge were considered for Tree Preservation Orders as

this could impact on the use of cranes or the Heavy Duty

Transporter (HDT) on approaches to the bridge location

from the temporary erection area.

2.4 Land Availabili ty

During the feasibility stage (GRIP Stage 3) land ownership

in the adjacent areas of the bridge was determined; this

was achieved inexpensively through searches of HM

Land Registry. This is vital if items are to be lifted over 

private land, or if a site compound and temporary erectionarea are required. The lack of a suitable area for 

temporary erection during the week preceding the

possession meant that Neasham Road Underbridge could

not practically be installed using the HDT method.

Consideration was also given to working space and site

access during the possession. Construction of temporary

steps on the approach embankments made access

between road and rail level easier. Without immediate

access to the site, the designer should take into account

walking distance between abutments and transfer of 

materials and equipment during the abutment preparationstages of construction.

 Advances in Rail Underbridge Replacements

Figure 2 - Neasham Road

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90 Railway Bridges - Today and Tomorrow

Paper 11 Advances in Rail Under bridge Rep lacements

2.5 Installation Techniques

Several techniques are available for the installation of 

bridges, the two most common techniques for 

Underbridge replacement are the use of cranes and the

HDT. The advantages of each method are listed in Table

5, however, at an early stage in the feasibility design, the

choice of installation technique can have a significant

impact on the choice of structure.

For the crane option it was important that a suitable

working area was available in the immediate vicinity of the

bridge site. The emphasis of the design is for light

components which can quickly be lifted into position. This

method is well suited to bridge decks accommodating a

single track as lifting radii become restricted with heavier 

decks for multiple tracks.

For the HDT it was vital that a suitable temporary erection

area was available close to the bridge (within one mile)

and that the road was suitable in terms of strength andwidth to accommodate the Transporter with the bridge

attached. The HDT facilitates attachment of the cill beams

to the deck or decks thereby reducing the number of 

possession activities. This method is well suited to wide

structures supporting multiple decks where access and

temporary erection areas are available.

2.6 Construct ion Depth

Finally, construction depth must be considered by the

designer. For railway bridges subjected to RU loading in

accordance with BS5400 part 2 [1], it is usual for fatigue

to govern the design in spans up to around 20m. Thus theuse of 355 grade steel offers no advantage over that of 

275 steel. For semi-through bridges the construction

depth, i.e. the distance between the top of the rail and the

deck soffit, can be considered as being made up of three

elements:

• Track Depth - the distance from the top of the rail to

underside of sleeper 

• Ballast Depth

• Structure Depth

Deck construction depths can be optimised in a number of 

ways before consideration is given to the deck

construction. It is, therefore, of significance that the

designer determines the need for ballasted track and rails

to be used by liaison with the Permanent Way Engineer.

Furthermore, consideration should be given to the use of 

tracklifts and their effect on the vertical alignment of the

track.

The use of ballasted track is preferred by Network Rail as

it optimises flexibility for future track works, however, this

is not always compatible with the existing headroom.

Many older bridges made use of waybeams to limit

construction depths, the challenge to the modern

engineer is to provide a solution of minimal construction

thickness, which maintains headroom, and improved train

ride quality.

Ballasted Track

Several options are available to the designer to limit

construction depth where ballasted track is required.

Table 1 presents the various options showing how track

and ballast depth can be minimised. The designer should

also be aware that reductions in ballast thickness may

have an adverse structural affect due to reductions in

wheel load distribution, in such circumstances

considerations shall be given to load dispersal and

protection to the waterproofing during the design.

Table 1 - Ballasted Track

Sleeper Type

Depth

Waterproofing

4mm membrane,

13mm protectivematting, 3mm

tolerance

Ballast

In accordance with

GC/RT5014 and

RT/CE/S/102

Sleeper 

In accordance with

RT/CE/S/049 and

RT/CE/S/029

Baseplate/pad

BS 113A rail

Total Construction

Depth

Concrete

(F 10)

20

250

204

10

159

653

Shallow

concrete

(EF 29)

20

250

165

10

159

633

Timber 

20

250

130

44

159

603

Steel

20

200

100

10

159

489

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91Railway Bridges - Today and Tomorrow

Direct Fastening Track

Where the installation of a ballasted track is not possible

other options are available to the designer. For the Ridley

Hall (NEC2/96) bridge, four options were considered as

detailed in Table 4. For differing spans the construction

depth of the deck may vary, however, the table gives an

indication of the savings in construction depth offered bythe Edilon system and other direct fixings to reinforced

concrete decks.

Structure Depth

Various standard forms of bridge deck have been

developed and adapted for use on Britain's Railways

since the 1950's. The Steel Construction Institute (SCI)

gives details, examples and descriptions of the various

forms of standardised bridges (A-Type to E-Type) in their 

Design Guide for Steel Railway Bridges.[5]

The forms of construction adopted by Hyder are

presented in Table 3, together with typical construction

depths. These include an adaptation of the Z-Type which

was adapted from the A-Type; the girder bottom flange is

offset from the centreline of the web to provide access

between the six-foot girder for inspection andmaintenance. For the proposes of this paper, only the U-

Deck is considered in detail

Table 3 - Construction Depths for Direct Fastening TrackEdilon direct fixing to

concrete filler beam

deck

300

N/A

Incl.

N/A

187 (Edilon)

487

Longitudinal timbers

on steel battle deck

300

25

250

10

159

744

Pandrol 'Vipa' type

clip direct fixing to

concrete filler beam

deck

300

25

45

0

159

529

Pandrol 'Vanguard'

type clip direct fixing

to concrete filler 

beam deck

300

25

20

0

159

504

Fixing Type

Depth

Deck

Waterproofing

4mm membrane, 13mm protective matting ,

8mm tolerance

Fixing system

Pad

BS 113A rail

Total Construction Depth

Figure 3 - Ridley Hall prior to installation of Edilon system

Paper 11 Advances in Rail Underbridge Replacements

Steel sleeper 

300

200

150

Concrete/ hardwood

sleeper 

300

250

200

Category of Track

In accordance with

GC/RT5014

1

2

3, 4, 5, 6

Table 2 - Construction Depths for Ballasted Track*

*GC/RC5510 recommends a minimum of 200mm to allow for 

tamping and distribution of wheel loads

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92 Railway Bridges - Today and Tomorrow

Paper 11 Advances in Rail Under bridge Rep lacements

Structure

Depth

(mm)

220

-

377

250

Construction

Depth

(mm)

824

487

981

744

Cross Section DrawingBridge

DSN1/2

Neasham

Road

NEC2/96

Ridley Hall

NEC1/20

Forge

Road

 ABE1/7

Sand

Lane

Girders

4 U-Deck

-

2 Semi-

Through

4 Z-type

No of 

Tracks

2x1

2

2

2x1

Deck

Construction

Composite

Reinforced

Concrete

slab

Battle

deck

Battle

deck

Table 4 - Bridge Deck Types and Construction Depths

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93Railway Bridges - Today and Tomorrow

3.0 The U-Deck Solution

The U-Deck solution was chosen for Neasham Road for 

its low construction depth and suitability for installation by

crane with minimal possession activities. U-Decks have

been successfully installed in several locations throughout

the UK including the East and West Coast main lines [16].

The Neasham Road solution has a span of 13.095m and

a skew angle of 25 degrees. The benefits of thisconstruction are simplified fabrication and erection,

improved appearance and reduced construction depth.

The U-Deck design

does away with the

traditional discreet

U-frames and

utilises a

c o n t i n u o u s

constraint to the

bottom flange from

the composite deck.The U-frame action

was then

considered to act at

unit centres as

detailed in Clause 9.6.4.2.2 of BS5400 Part 3 [2]. This

approach meant that web stiffeners were not required on

the outside face of the girders and the often limiting

fatigue Class F [3] weld between the web stiffener and

underside of the top flange was omitted, permitting a

higher value fatigue Class D. The steel/concrete

composite floor design made use of a single floor plate,

which was integral with the main girders, reducing

construction depth to 220mm, compared to 250mm for astandard battle deck. This saving in construction depth

facilitated the provision of ballasted track, whilst

maintaining the existing headroom and avoiding the need

for a track lift. The solution is ideally suited for short spans.

Steelwork

The U-Deck was fabricated by welding the girder webs

directly to the single deck plate. Transverse stiffeners and

shear studs were then welded to the top side of the deck

plate before the deck was in-filled with concrete to provide

a fully tanked bridge deck ready for waterproofing. The

width between inner faces of the girder webs was chosento allow adequate clearance between the sleeper ends

and the waterproofing protection boards for ballast,

typically this dimension should not be less than 100mm or 

2.5 times the ballast size, however, in practice it is often

the structure clearance gauge which governs the overall

distance between the top flanges of the cess girders or 

robust kerb.

Robust Kerb

The robust kerb requirements of GC/RC5510 [12] were

accommodated by increasing the depth of the cess girder 

such that the top flange was a minimum of 300mm above

track level. The top flange was then at the same level as

the cess walkway which was supported on brackets

cantilevering from the side of the cess girder. The

increased girder depth required the deck to be sufficiently

wide such that the cess girder does not infringe the

structure gauge.

Inner Girder 

The top flange level of the inner girders was lowered

below the structure gauge so that the inner girder top

flanges were accommodated outside the lower sector 

structure gauge as defined in Appendix 1 of GC/RT5212[11]. Designers should note that this area has been the

subject of a Network Rail derogation [10] to reinstate the

area previously defined as available for bridge girders in

 Appendix B of 

the now

w i t h d r a w n

G E / R T 8 0 2 9

[15]. The

height of the

cess girder top

flange is

t h e r e f o r e

limited to

110mm above

rail level.

3.1 Analys is and Design

Robustness

The flush soffit plate of the U-deck makes it less

susceptible to local distortion and buckling and the small

outstand of the flange beyond the main girder web greatly

reduces the likelihood of a flange peeling type failure.

Typically the outstand was limited to 50mm which was

further reduced by a large fillet weld to leave as small anactual outstand as possible without reducing the fatigue

classification of the deck plate to class G.

Collision Impact Protection

In low headroom situations the deck is required to sustainthe collision effects specified in BD37/01 [6]. In the case

of Neasham Road an independent impact collision beam

was provided beneath the safe cess walkway. Having

Paper 11 Advances in Rail Underbridge Replacements

Figure 4 - Neasham Road bridge prior to casti ng the concrete deck

Figure 5 -Neasham Road bridge U-Deck l ifted by 1000 tonne crane

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94 Railway Bridges - Today and Tomorrow

independent bridge decks and collision beams increased

the likelihood of the railway remaining operational in the

event of a collision. The alternative to providing the

independent protection beam would mean the bridge

bearings would need to be designed to accommodate the

500kN horizontal and vertical (uplift) forces associated

with collision. In this case the impact collision beam was

anchored into the cill beam to resist applied horizontal and

vertical (uplift) loads in accordance with BD60/94 [7].

 Addi tional ULS requirement

U-deck cross members were assumed to transmit all deck

loads into the main girder web by shear via the deck

stiffener/web welded connection. In view of the fact that

this critical connection cannot be inspected once the deck

slab has been completed, it was considered desirable to

have alternative load paths available to ensure that

premature failure does not lead to excessive deformation

of the structure. To this end it is also assumed that the

deck plate must be capable of carrying the loads into the

main girder web without reliance on the rib/main girder web connection. This additional ULS requirement was

considered in the design of the web/flange (deck plate)

fillet welds.

4.0 Crane v Heavy-Duty Transpor ter 

Buildability is a major factor in the choice of any bridge

deck replacement. The availability of land both

immediately adjacent to and local to the bridge site can

dictate the method of installation which in turn can

influence the form of the structure. Furthermore, with

possession availability at many sites limited to Christmasand Easter blockades, consideration needs to be made

for weather conditions and the possibility of high winds

which may hamper attempts to lift structures by crane.

The crane method

requires land to be

available in the

immediate vicinity

of the bridge site to

allow the crane

and, importantly, its

outriggers to be

p o s i t i o n e d ;c o n s i d e r a t i o n

should also be

given to the

delivery to site of 

the new structure,

typically on

articulated wagons.

This method may

limit the width of the structure, which ideally should be

prefabricated outside of any possessions. In the case of 

Neasham Road underbridge the 1000 tonne crane was

used for lifting the new structures and cill beams in turn. Adequate width was avai lable within the highway

boundary while no suitable working area was available for 

the erection of the bridge on temporary trestles.

The Heavy Duty Transporter (HDT) method requires an

adequate area in close proximity to the bridge site to

facilitate fabrication of the deck prior to the possession.

Usually this area will be within 500 metres of the bridge

site to limit the time taken for the HDT to traverse between

the temporary and permanent sites. This method of 

installation will typically include attaching the cill beams to

the deck, loading the deck with ballast and the addition of 

any ancillary ballast retention units. This operation willrequire crane lifts to erect the components of the bridge,

which can be susceptible to high winds, therefore,

consideration needs to be given to erection in the

temporary location in the days or weeks prior to the

planned possession. The strengths and weaknesses of 

the crane and HDT method of installation are compared in

Table 5.

The Heavy Duty Transporter method was successfully

utilised at Ridley Hall (ELR: NEC2/96). This choice was

influenced by the limited working space immediately

adjacent to the bridge which would have made the craneoption impractical; limiting the lifting capacity to 14 tonne

would have required the deck to be constructed in several

sections with in situ stitches. In this instance the deck was

attached to the cill beams in the week leading up to the

possession, then driven into position during the

possession. The use of the HDT facilitated the use of a

monolithic reinforced concrete deck without the need for 

stitch joints, thereby reducing the number of possession

activities.

The ability to undertake a single lift of the deck and cill

beams offered significant time savings to the Contractor 

during limited possession periods. In this instance the

deck units are attached to the cill beams and the entire

structure lifted in one operation. Where track access is

remote or limited, ballast can be stacked on the deck prior 

to installation to

reduce the need to

transport materials

over long distances.

The crane method

was successfully

utilised for Neasham

Road (DSN1/2).Here the choice was

influenced by land

availability; the road

was sufficiently wide

to accommodate the

1,000 tonne crane,

combined with the

shortage of suitable

working areas to erect the bridge for use by the HDT. In

this instance the deck was chosen such that each unit

could be easily transported as a single unit. The U-deck

was fabricated, concrete deck cast and waterproofingapplied off site. The units were then driven to site during

the possession weekend; the sizes of the units were such

that no additional site fabrication was necessary. Careful

Paper 11 Advances in Rail Under bridge Rep lacements

Figure 6 - Forge Road bridge deck and cil l beams installed by HDT

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95Railway Bridges - Today and Tomorrow

planning of the sequence of delivery of the deck units and

cill beams was required due to the limited road width and

restrictions on site access.

 Accuracy of installation was a consideration taken intoaccount by the designer. Clearance to the railway

structure gauge is critical and often reduced to a minimum

to tie into existing abutments and embankments.

However, consideration needs to be given to the method

of installation and time available to achieve accuracies

with care taken to ensure they are specified too onerous.

The accuracy of the HDT installation is governed by the

lowering of the support over the axles, as the deck is

lowered into position; there is an associated transverse

movement which results from the cam effect of the

lowering mechanism. As all four corners of the deck are

landed simultaneously there is little opportunity to man-handle the structure into its final position. A time

consuming system of trial and error will pursue if a high

degree of accuracy has been specified by the designer.

Contrast this with the crane method where the operator 

can take the weight of the element, allowing minute

adjustments to be made to the final landing position of the

deck.

5.0 Conclusions

It is essential that the contractor and designer work

closely together to produce a solution which is practical to

build within the constraints of a railway possession.

 Attention to details and tolerance at an early stage,

combined with ensuring they are achievable in a timely

and cost effective manner, will ensure the success of the

scheme.

Headroom and construction depths are often found to be

at odds with the preference for ballasted track. There are

numerous options available to the designer to reduce

construction depth and early liaison with Network Rail will

ensure a suitable compromise is achieved. Where

headroom of 5.3m can not be achieved, the preference is

to provide independent collision protection beams,allowing replacement without affecting the safe operation

of the railway.

The use of the U-Deck is a cost effective and practical

solution for spans up to around 20m and offers significant

advantages in terms of durability and flexibility of 

installation methods over other solutions. Furthermore,

the structure depth of 220mm offers a saving of 30mm

over the traditional steel battle deck.

The designer should pay attention to the deck ends and

interaction between the different structural elements. Thedesigner should make use of three dimension computer 

models to verify their design to avoid clashes of pre-

fabricated elements.

Finally, the successful implementation of the project will

be achieved if careful planning is implemented at all

stages of the design process by the design and

construction team.

Paper 11 Advances in Rail Underbridge Replacements

Table 5 - Crane v Heavy-Duty Transporter 

Crane

Landing tolerance easily

achieved of +/- 5mm.

 Availability for use for generalsite lifting of ancillary

components and materials.

Lower cost of equipment hire.

Heavy Duty Transpor ter 

Minimal risk of lost lift due to high

winds.

Single lift for deck, cill beam,transition slabs, ballast etc.

minimises possession activities.

High lifting capacity. Weight Limit

of 27 Tonne per axle (Typically 6

or 8 axle units are used).

Crane

Increased risk to lift as a result of 

strong winds.

Large working area requiredadjacent to final location for 

crane outriggers.

Multiple lifts for cill beams, deck,

walkways etc.

Heavy Duty Transporter 

Increased cost per contract lift.

Working area required in closeproximity to final location for 

erection of bridge components.

Tolerance easily achieved of +/-

25mm.

Strengths Weaknesses

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96 Railway Bridges - Today and Tomorrow

 Acknowledgments

The author would like to thank May Gurney Rail and

Network Rail (LNE territory) for their permission to publish

this paper. The views expressed are those of the author 

and not Network Rail or May Gurney Rail.

References

1. BS5400 part 2 (1978) Steel concrete and composite

bridges, Specification for Loads. BSI.

2. BS5400 Part 3 (2000) Steel concrete and composite

bridges, Code of Practise for design of steel bridges. BSI.

3. BS5400 part 10 (1980) Steel concrete and compositebridges, Code of practice for Fatigue. BSI.

4. Department for Transport (2004) The Future of Rail -

Making it Happen. HMSO.

5. D.C. Iles (2004), Design Guide for Steel Railway

Bridges, P138. Steel Construction Institute.

6. Highways Agency (2001) BD37/01 Loads for Highway

Bridges, Design manual for Roads and Bridges. HMSO.

7. Highways Agency (1994) BD60/94 The Design of Highway Bridges for Vehicle Collision Loads, Design

manual for Roads and Bridges. HMSO.

8. Highways Agency (1996), TD27/96, Cross Sections

and Headrooms, Design manual for Roads and Bridges.

HMSO.

9. HSE (1994) The Construction (Design and

Management) Regulations. HMSO.

10. Network Rail (2204)Deviation Certificate Number 

04/050/NC.

11. Network Rail (2003) GC/RT5212, Requirements for 

Defining and Maintaining Clearances, Issue 1. Railway

Safety.

12. Network Rail (2000) GC/RT5510 Recommendations

for the Design of Bridges, Issue 2. Safety and Standards

Directorate.

13. Network Rail (2004) NR/CE/GPG/003 Prevention of 

Bridge Strikes, A Good Practise Guide for Transport

Managers, Issue 1. Safety and Standards Directorate.

14. Network Rail (2004) RT/LS/P/007, Project

management and the Environment, Issue 2. Network

Rail.

15. Railtrack plc (2000) GE/RT8029 Management of 

Clearance and Gauging Issue 1. Safety and Standards

Directorate.

16. Sadler & Wilkins (2003), Short Span Railway

Underbridges: Developments, NSC Vol 11 No 6. Steel

Construction Institute.

17. www.networkrail.co.uk/companyinformation/index.htm

Paper 11 Advances in Rail Under bridge Rep lacements

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97Railway Bridges - Today and Tomorrow

Paper Twelve

Forth Bridge

Safety and Production

Malcolm Hyatt

BALFOUR BEATTY CIVIL ENGINEERING

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98 Railway Bridges - Today and Tomorrow

1. Introduction

The Forth Bridge is one of the wonders of the world. The

refurbishment of the Bridge is essential to ensure that it

both remains operational and is there for generations to

come.

Safety is everyone's number one priority but sometimes

achieving what is required is not so easy. On the bridge,the team has to date maintained an excellent safety

record while achieving production.

The aim of this paper is to try to demonstrate that is

possible to continually minimise safety risk and maintain

or increase production efficiencies.

We will talk about some of the safety measures that are in

place to combat the hazardous working environment that

exist on the bridge, and the efficiencies that the project

continues to gain.

2. About the Forth Bridge

The 2.5 km. (1.5 mile) Forth Railway Bridge, the world's

first major steel bridge, with its gigantic girder spans of 

521 m. (1710 ft.) ranks as one of the great feats of 

civilization. It was begun in 1883 and formally completed

on 4 March 1890 when HRH Edward Prince of Wales

tapped into place a 'golden' rivet.

The bridge was constructed by Tancred-Arrol, and

designed by civil engineers Sir John Fowler and Benjamin

Baker. The design was finally developed after the TayBridge disaster.

The balanced cantilever principle was adopted. The main

crossing comprises tubular struts and lattice-girder ties in

three double-cantilevers (named Queensferry (Southern)

- Inchgarvie (Middle) and Fife (Northern)), each

connected by 105 m. (345 ft.) 'suspended' girder spans

resting on the cantilever ends and secured by man-sized

pins. The outside double-cantilever shoreward ends carry

weights of about 1000 tonnes to counter-balance half the

weight of the suspended span and live load.

Each of the 110 m. (361 ft.) high double-cantilevers is

supported on well-founded granite faced piers. The

bridge's construction involved the employment of 4,000

men at times, the use of 54,000 tonnes of steel and

driving 6,500,000 rivets. Its total cost was £3,200,000.

During operations, rescue boats were stationed under 

each cantilever saving at least 8 lives, but still at least 57

men lost their lives, and it is alleged that over 400 were

injured. The fact that a temporary hospital was set up in

the grounds of a local hostilely gives an indication of the

level of accidents and injuries.

Today, our aim is for zero accidents or incidents and with

changes in law, vast improvements in plant, materials

there is no reason why this should not be a realistic goal.

3. The Present Contract

Network Rail (NR) carried out a structural and

maintenance assessment of the structure, which resulted

in 2001, Balfour Beatty being awarded Civil Engineering a

Co-Operative Non-Binding Agreement Contract to

refurbish approximately 220,000m2 of the 450,000m2 of 

bridge members, which is to run until 31st. March 2009.

Within this agreement Network Rail instruct work by the

issue of an annual Work Bank Instruction (WBI) which

details Members to be refurbished.

In Year 1, it was the intention to refurbish a number of 

selected bridge members to learn about the constraints of 

working efficiently on the structure, so that information

could be gained to allow movement to agreement of 

annual target costs with pain/gain mechanisms.

Sub-contractors that are working with BBCEL to carry out

the works are as follows:

South

Coatings Pyeroy

 Access provision SBG

Steel repairs RBG

North

Coatings, Access provision and Steel repairs are all

carried out by Palmers

BBCEL are the Principle Contractor, providing all welfare

facilities, delivering all materials to the workface, ad allprogramming co-ordination functions.

4. The Contract Requirement

The basic requirement is to remove the existing lead

based paint and provide in its place a glass flake epoxy

coating system which is designed to a 20 year life.

However, it is hoped that with a well managed

preventative maintenance programme that the system will

last a lot longer.

 A brief listing of the sequence of activities is:

• Programme of works developed and agreed

• Preparation of Risk assessments and method

statements

• Access scaffolding designed and agreed

• Materials taken out to the bridge by barge or rail

• Access erected in accordance with design

• Encapsulation erected

• Steel repairs assessed by NR

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99Railway Bridges - Today and Tomorrow

• Steel Repairs carried out

• Blasting and Painting

• Encapsulation dismantled

• Access dismantled

The co-ordination of the above activities requires accurateand detailed planning with input from all parties to ensure

that safe systems of work are developed with a view to

achieving or bettering the required outputs.

5. Safety - General

BBCEL operate under a Contractors Assurance Case

related to Link-Up registration as well a being accredited

to ISO 9001,14001 etc.

 All of our processes are controlled by a document called

the Project Management Plan, which describes themeasures and documents required to carry out the Works.

Examples of documents that are controlled are:

• Risk assessments

• Method Statements

• Works Procedures

• Programme

• Environment Controls

The Forth Bridge Refurbishment Project has not had a

reportable accident since commencing in April 2002.

That's over 1.7million man-hours without a reportable

accident.

We believe this has been achieved by proactive safety

management by main contractor and sub-contractor 

management, and the positive attitude of the workforce.

We consider that involvement of the Workforce is

essential to maintaining the level of safety that is required.

 All are aware that on a Project of this nature, that

complacency may well be one of the biggest dangers. To

this end it is important to keep reinforcing the safety

message. This is done mainly through the following:

• Safety Inductions given as a minimum at the start of 

each Year 

• Safety Representatives participate in safety meetings

and safety inspections

• Work Face Risk assessments carried out by the

Workforce. These are checksheets that the gang will go

through each morning or at change of location or 

activity, to assess the local risk to themselves or to

others

• Briefing sessions for new themes or topics

• Weekly safety inspects which involve the workforce

• Regular toolbox talks covering a range of subjects

• Implementation of a Behavioural Based Take C.A.R.E.

It is worth spending some time on "Take C.A.R.E."

C Conscious A  Actions

R Reduce

E Errors

Conscious Actions Reduce Errors

Whilst we have this safety record we still have a small

amount minor accidents, and incidents.

The "Unsafe Act" can be described as the the route cause

of all accidents. In the majority of cases the "Unsafe Act "

results in no consequences, or sometimes it might resultin a near miss or property damage. However, under 

different condition the same unsafe act might result in

minor or even major injury.

So the aim of this scheme is to attempt to reduce the

occurances of the Unsafe Act.

The idea is to engage the workforce in a programme of 

observations of their group's activities, assessing the

outputs of these observations against a set of agreed

criteria, and agreeing actions to improve on the

observations.

We view this as a long term process and are looking

forward to long term reduction in the small quantity of 

unsafe acts and consequently minor accidents and

incidents.

6. Programme

The traditional belief that when painting the Forth Bridge,

you just start at one end, work towards the other, and

when you get there you start again is just not true.

In fact, the programme or sequence of work is developed jointly between Network Rail and BBCEL for the

implementation works, and are based on Network Rail

Requirements, safety criteria and budget.

These are:

• Member criticality - Network Rail identify through

detailed inspected and structural assessment, the

bridge members that are in most need of refurbishment

• Global Loadings" - the restrictions caused by the

strength of the bridge on the weight of scaffold atvarious locations and the effect of the wind due to the

encapsulation

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100 Railway Bridges - Today and Tomorrow

• Safety - Exclusion Zones. During access erection an

exclusion zone is set in areas below to ensure no other 

operations are carried out at the same time

• Safety - Manual Handling. As much as possible

access activities are programme to ensure that manual

handling is minimised. An example of this would be to

programme an access dismantle sequential with an

adjacent access erect

• Budget

7. Access Provision

The highest point of the bridge is approximately 306ft

above mean water level, and the lowest is a matter of a

few feet, and as such all access work on the bridge is

deemed to be work at height.

 All activities on the Bridge rely on the provision of access

scaffolding to enable the work to be carried out safely andthe provision of adequate environmental controls.

The access scaffolding is provided by sub-contractors

SGB and Palmers, who employ up to 30 scaffolders each

on the Project. They each employ scaffolders at various

levels up to and including IRATA 3 grades for abseiling.

Believe it or not the need for abseiling techniques is

limited as in most cases the scaffolding for a particular 

member can be safely commenced with more traditional

techniques such as double lanyards, running lines or 

retrievable inertia reels.

We employ a safety boat to monitor all activities that

require personnel to be protected from a fall, i.e. leading

edge activities. The safety boat is an essential part of the

safe system of work for the access provision and as such

is linked by radio to all access squads and Bridge Control.

 A substantial amount of scaffold is erected above the track

which provides its own challenges. The safe system of 

work that has been developed is as follows:

• All personnel that are working above the track on

scaffolding or encapsulation activities are subject to

medical surveillance

• With each squad working above the track is a COSS

and lookouts as appropriate. These safety critical

personnel work as normal on the track and control the

activities above.

• The COSS will ensure that all personnel are briefed

and will test the Safe System of Work

• The lookout will upon sight of a train, signal in the

prescribed way

• Upon receiving the signal the personnel will stop work

securing all materials

• When the train has past the COSS will give the go

ahead to recommence works

 As the system of unassisted lookout is the lowest of the

Safety Hierarchy, we have endeavoured throughout the

period of the Project to move up the hierarchy and have

carried out several trials with ATWS.

Initially, in situ trials were carried with "Track 02", but

unfortunately, due to various reasons at that we couldn't

utilise this system, but we have not given up and are at

present, with Network Rail managers are evaluating the

"Minimel" system, which we hope will prove successful.

 Apart from the obvious personnel safety issues, there is a

secondary reason why we are considering the use of this

system. Approximately 200 trains use the bridge through

the working day, and we have recorded that up to 30% of 

the working hours can be lost due to stoppages to allowtrains to pass.

The lookouts give warnings on first sight of a train, which

on this bridge is generally far greater than the minimum

sighting distances in accordance with the Rule Book. The

 ATWS system would be set so that the warning would be

given at a distance in accordance with the Rule Book but

less than that given by the lookouts. We anticipate that a

saving of between 5 and 10% could be achieved on

scaffolding costs if this was implemented in the future.

 A simple but effective efficiency, was changing from ladder 

access to staircase access. At the south end of the

project, access to the work areas is gained via a 500m

trek along walkway in the approach spans. BBCEL,

inherited a system where changes in height in access

walkways were accomplished by the use of ladders. One

of these ladders was positioned at the Southern Jubilee

tower and was approximately being 8m in height.

Consequently, during the walk out to the work areas

approximately 50 men would have queue to climb the

ladder in the morning and again when they left the bridge

at night. This equated to inefficiency off about 300man

minutes a day times. The change from ladder to staircase

has eradicated this problem ensuring that personnel get tothe work areas quicker which means more time spent at

the workface.

In general all ladders on the main walkways have now

been replaced by staircases. However, due to the nature

of the access scaffolding design based on all of the

constraints outlined above, it is not always possible to

provide access staircase actually at the workplace,

therefore, ladders are provided.

To keep manual handling of materials and tools to a

minimum a series of mini hoists, gin wheels are utilisedbased on the circumstances.

Paper 12Forth Bridge - Safety and Production

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101Railway Bridges - Today and Tomorrow

Through constant review of the processes or methods for 

each activity, which includes ways in which we can

improve efficiency while maintaining the safety attitude

the scaffolding activities are on the whole becoming more

efficient.

Some examples of this are two adjacent identical vertical

columns. The first one that was scaffolded in 2002/2003

took 3392 man-hours while the adjacent column in 2004took 2223 man-hours, an efficiency of 34%. Another 

example is the access erection of the suspended spans.

The Northern Span took 8039 man-hours in 2003, while

the Southern Span took 6776 man-hours, an improvement

of approximately 16%.

The removal of the existing old paint system in

preparation for the new system requires that the steelwork

blast cleaning to bare metal with a profile of SA 2½. Steel

that is corroded or has lost section sufficient to make

redundant or near redundant is repaired or replaced.

Obviously, the removal of the paint system using the tried

and tested method of dry grit blasting, is potential both

hazardous to the operatives and the public, and could be

extremely hazardous to the Environment.

The access scaffolding that is erected to provide a stable

platform to allow these operations to be carried is

designed to be encapsulated using a heat applied "Shrink

Wrap" polyethylene material.

BBCEL introduced this method at an early stage, and

immediately proved itself more efficient than previously

used cladding material for the follow reasons:

• Comes in rolls that are easier to transport and handle

• Can be cut and sealed around incoming members and

scaffold tubes etc., thus ensuring that no grit escaped

and minimised the amount of rain water that enters an

area. This was previously extremely difficult to achieve.

• Better environmental protection

• Is more resilient than traditional methods of cladding

• Is safer to erect and dismantle

• Manufactured to European Standards

• Traceable fire resistance

8. Coatings

The system of encapsulation described above protects the

environment from the effects of the paint removal process as

well as the personal not involved in the actual operation.

The removal of the original lead paint system is carried out in

accordance with current legislation including but not limited

to:

• Network Rail Company Standard

• The Control of Lead at Work Regulations

The existing lead paint is removed from the bridge by the

process of dry grit. Dry grit removal is used as it obtains the

best steel profile and is easier to contain.

Before grit blasting can proceed the following precautions arein place:

• An appropriate Risk Assessment has been carried out

• All persons who may come into contact with lead working

must be subject to a monitoring of blood level concentration

which is carried out by a Medical Practitioner or body

approved by the H.S.E. There is a statutory trigger level of 

70 milligrams of lead per 100 millilitres of blood, at which

point the HSE must be notified. On the bridge we have

never had personal whose lead/blood levels reach this point

as we generally take action when or if, through themonitoring process the there is a rise from the norm, the

person is talked to ensure that all of the precautions that

should be in place are being utilised.

• Some control measures are:

1. Blood monitoring

2. Use of full face masks are air fed

3. Full protective clothing

4. Personal hygiene - washing prior to eating or 

drinking

5. Provision of suitable facilities for changing out of 

lead contaminated clothing which are isolated from

clean areas and canteens

6. Shower facilities

The recovery of the spent grit is by vacuum suction which

drastically reduces the amount of manual handling required.

We currently have two such systems set up, one at

Queenferry and another at Fife. In year 4 these systemsremoved well over 1000 tonnes of spent grit. Whilst

expensive to set up year on year these systems reduce

overall costs (mainly labour) by up to 40%.

Despite these constraints the project has continued to show

efficiency improvements year on year, through continual

review of methods etc..

Examples of production efficiencies while maintaining safety

culture are as follows:

• The first one is the suspended spans. The northern spanwas coated in 7882 man-hours in 2004, while the

southern span took 6772 man-hours, an efficiency of 

about 14%

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• The second is the comparison between the east and

west bottom booms at Queensferry. In 2003, it took 5386

man-hours to west booms, while in 2004, 4516 man-hours

were used. An efficiency of 16%

9. The Project Overall

The safety challenges for this project are immense, with

working from height, working over water, adverse weather conditions, over and around trains, with lead based paints

etc. The need to work extremely safely is paramount and

to improve efficiencies.

The safety record speaks for itself, although as explained

earlier, we are conscious that complacency could be our 

worst enemy. And have therefore put in place measures to

counter this and continue to strive for our goal - ZERO

 ACCIDENTS.

We have also talked about continuing to achieve

production efficiencies and have given a few examples.

Year 2 (2002/2003) has been used as the efficiency

benchmark for future performance, as year 1 was a year 

of setting up and learning.

The overall project efficiency has continued to be

achieved since and in Year 4 and the overall project cost

of producing one square metre of painted bridge member 

was 80% of that of Year 2, i.e. a reduction of 20%.

Moving forward it is expected that by the end of Year 6 a

further 10% efficiency would be achieved.

10. Conclusion

Hopefully, this Project can be taken as an example of one

where Safety the No. 1 priority, and through constantly

reviewing methods, process production efficiencies are

still being achieved.

Certainly for a long term Project such as this it is possible

to maintain an excellent safety record and produce

production efficiencies.

102

Forth Bridge - Safety and Production

Railway Bridges - Today and Tomorrow

Paper 12

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103Railway Bridges - Today and Tomorrow

Paper Thirteen

Skills Competency in the Painting

Industry: The Industrial Coatings

 Applicator Training Scheme

Dr. Stuart Lyon

INSTITUTE OF CORROSION

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104 Railway Bridges - Today and Tomorrow

Summary

This paper describes the background, structure and

operation of the Industrial Coatings Applicator Training

Scheme (ICATS). The benefits that will accrue to clients in

reduced lifetime cost of asset ownership, and to

contractors in employing a qualified and certificated

workforce, are highlighted.

Background

The costs of corrosion to the UK economy were first

analysed by a DTI committee chaired by Dr. T.P Hoar of 

Cambridge University and set up in 1969 by the then

Minister for Technology (Tony Benn). The main

conclusions of the Hoar Report , published in 1971, were:

(a) that the costs of corrosion were approximately 3-4% of 

GNP per annum, (b) that about one-quarter of these costs

could be saved by the application of then currently known

technologies and (c) that better training and dissemination

in the industry was essential in order to contain costs. Asa direct consequence of the Hoar report, the Corrosion

and Protection Centre came into being at UMIST (now

The University of Manchester) to provide postgraduate

education, academic research and consultancy into the

corrosion protection industry. Soon afterwards, the two

main professional interest groups in the UK merged their 

activities to form a learned professional society, now

known as The Institute of Corrosion.

Similar surveys undertaken in the USA and Japan shortly

after the publication of the Hoar report arrived at very

similar conclusions. More recently, an updated surveywas commissioned in the UK. Although more limited in

scope this estimated that the economic cost was still of 

the order of 2-3% of GNP per year. It is rather difficult to

conceive the scope of such losses however an effective

(albeit naive) way is to consider an annual loss of 3% of 

GNP as equivalent to the entire infrastructure of the

country disintegrating (due to corrosion processes) in

between 30-40 years. Or, on a more personal note, that

corrosion costs around £600 per capita per year;

equivalent to around 1-2p in the pound for each tax-payer.

Coating Inspection

Since its formation, the Institute of Corrosion (ICorr) has

been pre-eminent in the promotion of training and

certification in the protective coatings industry. Schemes

for the training of supervisors and foremen were

developed in 1975, with the support of the Construction

Industry Training Board (CITB); however, these were not

initially successful. Later, in 1978, a scheme for painting

inspector certification was set up at Bircham Newton and

further developed in collaboration with the US society

NACE. Unfortunately, this scheme was withdrawn from

the UK in 1987.

Starting again in the late 1990's, ICorr developed an

entirely new scheme for coating inspectors that was

compliant with EN 45013 "General criteria for certification

bodies operating certification of personnel". This is

currently delivered on behalf of ICorr by Argyll and Ruane

Ltd at their training centre in Sheffield. These courses,

which now include Coatings Inspection (paint, metallic,

pipeline and fire-proof) and Cathodic Protection, are

highly successful. Currently there are well over 2000

persons certificated at Levels 1, 2 and 3. ICorr inspectors

work in all sectors, and at all levels, of the protective

coatings industry and the ICorr qualification is recognisedas a benchmark standard worldwide.

Unfortunately, coating inspection does not, by itself,

guarantee a satisfactory job. Inspectors, will generally

focus on key aspects of the coating application process

while ensuring compliance with specifications. On the

other hand, poorly trained coating operatives (e.g.

blasters, painters and sprayers) are likely to try to make

their job as easy as possible and subvert in some way the

inspection process.

Coating Failures

Surveys, carried out by ICorr and others, have shown that

in the period 1982 to 1992 over 80% of coating failures

were due to poor surface preparation or application. More

recently, in the period 1992 to 2002, such failures have

been compounded by the introduction of new coatings

formulations that are much less tolerant of traditional

surface preparation methods and require novel methods

of application.

Figure 1 illustrates a comprehensive coating failure on

bridge steelwork several years after maintenance; indeed

it looks as though no work had been done at all. This poor 

result is due to a lack of understanding, by the contractor 

and operatives, of the surface preparation requirements of 

modern coating systems. Rust-through and blistering isclearly evident.

Paper 13Skills Competency in the Painting Industry

Figure 1 - Poor surface preparation

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105Railway Bridges - Today and Tomorrow

Figure 2 shows adhesion failure caused by solvent

retention (premature over-coating), also as a result of 

poor contractor/operator understanding. These failures

are both premature, unsightly and require urgent

remediation and neither was prevented by coating

inspection.

Competencies

Currently, the only way to demonstrate competence as a

painter or coating applicator is via the relevant NVQ at

Level 2. However, it is only very recently, after extensive

collaboration between ICorr and CITB, that this has been

extended to include competencies relevant to industrial

coatings application. Holders of current NVQs are most

likely to be assessed for commercial decorating, which is

not at all the same as effectively painting structural

steelwork. Also, although NVQs may demonstratecompetency, they do not include training nor are they a

certification scheme.

In May 2002 The Institute of Corrosion promoted a

conference in York to review current training in the

industry. Over 50 delegates attended representing major 

interests including clients, contractors and coatings

manufacturers. The outcome of was the formation of an

industry-wide task group with the remit to develop a new

training and certification route for artisan painters and

coatings operatives in the industry. Membership of the

task group comprised stakeholders from all industry

sectors including: Network Rail, Highways Agency (HA),CITB, Corus, National Grid/Transco, British Coatings

Federation (BCF), British Constructional Steel Association

(BCSA), and the Association of Consulting Engineers

(ACE). The outcome of this task group was the Industrial

Coatings Applicator Training Scheme (ICATS), which is

currently being rolled out across the UK.

Sector Schemes

National Sector Scheme (NSS) specifications are

designed to provide a quality management system for 

Highway Works, compliant with ISO 9001:2000. They arealso consistent with the HA requirement for evidence (by

certification) of a trained and competent workforce. Thus,

simultaneously with the introduction of ICATS, NSS

Committee 19: "Corrosion Protection of Transportation

Infrastructure Assets", was constituted, with the Institute

of Corrosion prominently represented. NSS 19 has now

produced the final draft for Scheme 19A: "Corrosion

Protection of Ferrous Materials by Industrial Coatings".

Great care has been taken, in drafting, to ensure that it is

essentially sector neutral. Thus, it is hoped that it may

also be used in other sectors. The NSS Scheme 19Adocument is due to be published as a draft for comment

before the end of 2006. After a short consultation period,

it shall then become mandatory for all new highways

works from mid 2007, thus enforcing a trained workforce.

Outside the transportation industry, National Grid/Transco

have, in recent Invitations to Tender for painting works,

also recognised the advantages offered by the use of a

trained and competent workforce by the ICATS route.

ICATS Training and Certi fication

The scheme is a comprehensive structured training

programme for the training, certification and registration of 

industrial surface preparation and coating operatives.

ICATS was produced in response to demands from

specifying/procurement authorities for evidence of 

practical training and competency in industrial surface

preparation and protective coating application that

complements other industrial skills sector schemes.

ICATS is owned by ICorr and managed by its trading

subsidiary Correx Ltd., as Certificating Body, on behalf of 

ICorr. The scheme is operated in accordance with the

relevant ICorr requirements document and controlled by

an Advisory Committee of stakeholder representatives

that reports to ICorr and Correx Ltd. The current scheme

provider is Argyll and Ruane Ltd., who also deliver the

ICorr Coating Inspector Training and Certification

Schemes.

ICATS delivers practical training in the workplace that is

not offered by any other training scheme. It incorporates

up-to-date practices and the use of modern high-

performance coating materials. ICATS exceeds the

evidence for training requirements of the existing NVQ

Level 2 for Decorative, Finishing and Industrial PaintingOperations.

Operation of ICATS

The scheme has a mandatory Basic Unit: "Industrial

Coatings Applicator" that comprises 6 modules:

• Health and Safety

• Site Access

• Plant and Equipment

• Surface Preparation

• Types of Paint and Application• Quality Control

Paper 13 Skill s Competency in the Painting Industry

Figure 2 - Coating adhesion failure

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106 Railway Bridges - Today and Tomorrow

The following optional Specialist Units may be taken after 

the Basic Unit:

• Abrasive Blast Cleaning Operator 

• Paint Sprayer 

• Thermal (Metal) Sprayer

• Water Jetting Operator 

Certification is awarded to candidates who havesuccessfully completed each individual Unit.

Companies wishing to have a workforce certificated under 

ICATS must first register with Correx Ltd. Upon

acceptance, registered companies may then nominate

experienced individuals from their company to attend an

ICATS "Train the Trainer" course. Subject to meeting the

acceptance criteria, these individuals then attend a 2 day

course at the Scheme Provider's premises.

 After successful completion of the course, certification as

an ICATS Trainer is awarded by Correx Ltd. Certificated

trainers are then qualified to train and assess operatives

in the workplace for individual certification as Industrial

Coating Applicator. Operative training need not be

undertaken by a company's own trainers but may also be

undertaken by registered trainers at another site as a

service, for example to smaller contractors.

Once certified, Trainers and Operatives are issued with a

certification card and are then qualified to work for any

company registered into the scheme. The scheme card is

valid for 3 years and re-certification is required after this

period.

Workplace trainers and the training of operatives is

subject to periodic audit at the company premises. The

audit process includes confirmation that procedures are

being correctly followed as well as observation of training

sessions to ensure that the learning outcomes are being

effectively imparted.

Delivery of ICATS

Operative training is delivered in the workplace of a

registered company by a registered ICATS Trainer.

Qualification for the Basic Unit should take approximately

40 hours, but is not required to be continuous and may be

taken at any convenient times. The training materials

comprise a high quality multi-media application available

on CD-ROM or via the Internet, backed up by printedspiral-bound books.

Benefits of ICATS

To the client the benefit of a properly trained, skilled and

certificated workforce is obvious as it will reduce the

incidence of premature coating failure, enhance coating

lifetime and reduce overall lifetime costs. As indicated

above the HA intend to make ICATS mandatory sometime

during 2007 for contractors who wish to tender for 

highways painting works and most local authorities will

follow this lead. Other major clients, including from theconstruction, infrastructure and offshore sectors have also

indicated that they will adopt and promote the scheme

Registered contracting companies will thus benefit as they

will have documentation of a competent workforce and will

therefore be eligible to tender for contracts where ICATS

is mandatory. It will also provide a competitive edge when

applying for registration on approved contractor lists.

Paper 13Skills Competency in the Painting Industry

Figure 3 - ICATS training materials

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107Railway Bridges - Today and Tomorrow

Paper Fourteen

Recent Developments in Strengthening

Technology and the Strengthening

/Reconstruction Decision

Lee Canning, Neil Farmer, Dr. Sam Luke and

Ian Smith

MOUCHEL PARKMAN/TONY GEE ANDPARTNERS JV

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108 Railway Bridges - Today and Tomorrow

Introduction

The use of fibre reinforced polymer (FRP) composite

materials for strengthening metallic, concrete and timber 

structures has developed significantly in the past 15

years. This strengthening technology is now generally

well accepted with the construction industry and a number 

of design guidance documents are available for the use of 

engineers.

However, the design methods and both technical and

practical limitations are relatively new to design

engineers, and specialist designers are required to ensure

an economic and practical design which is critical for a

successful installation of the FRP strengthening scheme.

Mouchel Parkman and Tony Gee and Partners have been

expert advisors and designers, acting in a joint venture

(the 'JV'), to Network Rail from 2001 for FRP

strengthening schemes on Network Rail infrastructure.

This commission came about after a report by Mouchel

Parkman on the benefits to be gained by Network Railusing FRP strengthening in 2000. Under this

arrangement, the design of every FRP strengthening

scheme on Network Rail infrastructure must be designed

by one of the JV partners and checked by the other at

Category 3 level.

Since the beginning of this commission, the JV has

undertaken the feasibility, design, check and site

supervision of FRP strengthening to 13 structures,

including overbridges, footbridges, an aqueduct, and an

underbridge, strengthening both cast iron and concrete

bridges. A further 8 structures are currently at feasibility or design stage. The technique is not a panacea, however,

and 5 structures which initially appeared suitable were

eventually rejected for FRP strengthening after detailed

consideration. The total capital cost of each scheme has

varied from £10,000 to over £2m, and provided total

cumulative cost savings of over £5m compared to other 

strengthening or reconstruction options.

The JV has also developed generic specifications for FRP

strengthening to metallic and concrete substrates,

undertaken road shows to disseminate the work done on

FRP strengthening to Network Rail engineers and to

obtain feedback, and advised on the content for CETANs.The knowledge developed during this period has also

been useful in providing information to be used in recent

design guidance documents.

The JV arrangement has enabled the problems

encountered, solutions and lessons learned to be collated

and reviewed in a relatively short timeframe, and to be

used in updating design methods, specifications and

CETANs.

 A short descript ion of current FRP strengthening

technology is provided, and two particular FRPstrengthening schemes presented below, with discussion

focussing on technical and practical issues, cost savings,

risk mitigation measures and management of residual

risk, and lessons learned. In addition, from the experience

gained in the JV, conclusions are drawn on what

situations are favourable for FRP strengthening as

opposed to other strengthening methods or 

reconstruction, and where this would not be the case.

FRP Strengthening Technology

Structural FRP strengthening methods developed initiallyin the military and marine industries, and have only been

transferred to the civil engineering industry since the

1980's. Initial applications comprised flexural

strengthening of reinforced concrete slabs and beams

and confinement strengthening of reinforced concrete

columns. Extensive research has been undertaken, and is

still ongoing, to further develop applications and design

methods for a variety of structural members and substrate

materials. The current status of the technology enables

flexural, shear, torsional and confinement strengthening of 

reinforced concrete, steel, wrought iron, cast iron and

timber members, with varying levels of design guidanceand maturity. The application methods are also wide

ranging, including in situ wet lay-up optionally

incorporating vacuum infusion and 'pre-preg' materials,

bonded pultruded or pre-formed plates, strips or bars, and

mechanically fixed plates. The FRP may be installed

unstressed, or prestressed by direct action or by structural

 jacking or load modification. The materials used include

carbon, aramid and glass fibres. However, by far the most

common application in the UK is flexural strengthening of 

reinforced concrete slabs and beams with carbon FRP

(CFRP) pultruded plates. There has also been significant

confinement strengthening of reinforced concretecolumns to improve impact, axial, flexural and shear 

strength. The design guidance for both these methods is

also the most developed.

Strengthening of metallic structural members is still

relatively novel and nearly always comprises flexural

strengthening by bonding FRP composite material to the

soffit of a beam, although design guidance is available for 

shear and other types of strengthening.

Preliminary theoretical and experimental work has been

undertaken on FRP strengthening of masonry arches, but

requires further development to enable safe and efficientdesign guidance. In particular, the difficulty in actually

assessing the real behaviour, strength and failure modes

of an arch is a barrier to developing useful design

guidance for strengthening methods.

 All the FRP strengthening methods currently used on

Network Rail infrastructure have comprised flexural

strengthening of cast iron girders or reinforced concrete

slabs or beams, although feasibility work has also been

undertaken on shear strengthening. This is probably due

to the fact that the majority of assessment failures on

Network Rail infrastructure are under flexure.

Paper 14Recent Developments in Strengthening Technology and the Strengthening/Reconstruction Decision

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109Railway Bridges - Today and Tomorrow

FRP Strengthening Case Studies

Maunders Road Overbridge, Stoke-on-Trent

The bridge is located in the

Milton area of Stoke-on-

Trent, Staffordshire (Figure

1). The structure was built in

the mid-1800's and carriesan unclassified road over a

cutting on the now disused

Stoke to Caldon Quarry

railway line. The effective

span of the bridge is 7.84 m

with a carriageway width of 

5.0 m and a 1.1m wide

footway on one side of the

carriageway. The bridge

comprises of 6 primary cast

iron girders, the middle

girders being spaced atapproximately 1.43m

centres and the edge

girders at 1.23m. These

girders support transverse

spanning brick jack arches

which in turn support road

base and asphalt

pavement.

 A structural assessment in

the late 1990s identified that

the main girders had a

capacity that would only

allow them to support 7.5

tonnes vehicles and the

edge girders only 3 tonnes

vehicles. One edge girder,

that which did not support a

footway, had been propped

by the addition of a steel

capping beam over a brick

wall. The prop was intended

to offer support to the cast-

iron edge beam, however,

the steel beam was badlycorroded with a perforated

web and was assessed as

providing no support to the

bridge girder.

The road was unclassified

and within a residential

area, however it was the

only route to a small

industrial area that included a steelwork galvanising factory.

The bridge was regularly trafficked by 40 tonnes heavy

goods vehicles (HGVs), -though the road layout was suchthat such vehicles could cross the bridge only slowly, and

normally only when oncoming traffic stopped to allow the

HGVs to negotiate

bends immediately beside the bridge. The highway

authority required the bridge to be strengthened to carry

40 and 44 tonne vehicles and 30 units of abnomal HB type

loading.

Several options, including

replacement of the bridge,

were examined. However,

the costs of diverting thepublic utilities that were

supported by the bridge

were substantial. The

cheapest option was to jack

up the bridge girders at mid-

span, thereby relieving the

dead and superimposed

dead loads, then bond

CFRP laminates either side

of the temporary prop before

the latter was de-stressed

(Figures 2 and 3). Thereby,the strengthened composite

section acts efficiently in

resisting both dead and live

loads.

Hammersmith Road

Bridge

Hammersmith Road and

Kensington High Street

(A315) in West London is

one of the major 

thoroughfares from the

London Borough of 

Hammersmith and Fulham

to the Royal Borough of 

Kensington and Chelsea and

on into Central London

(Figure 4). The route runs

approximately parallel to the

 A4 and is a necessary link

for local businesses and bus

services. Approximately

perpendicular to the A315,

along the borough boundary,is Network Rail's West

London Line and a branch of 

London Underground's

District Line. The District

Line branch has the specific

purpose of serving the two

busy exhibition halls on

either side of Hammersmith

Road: Earls Court and

Olympia, while the West London Line (WLL) connects

Falcon Junction (near Clapham Junction) and Willesden

West London Junction. At the intersection of the A315and the two railway lines there is a road over rail crossing.

This structure is known as Hammersmith Road Bridge.

This is a three span bridge crossing the single track

District Line in its western most span, the two track WLL

Paper 14 Recent Developments in Strengthening Technology and the Strengthening/Reconstruction Decision

Figure 1 - Maunders Road overbridge

Figure 2 - Jacking out dead load on Maunders Road overbridge

Figure 3 - CFRP strengthening on jacked structure

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110 Railway Bridges - Today and Tomorrow

in the centre span and a disused siding within the eastern

span. The LU District Line is fourth rail electrified and the

Network Rail WLL is third rail electrified with a crossover 

within the structure.

The two siding spans have a span of 5.25m with the

central span being 10m. The carriageway of the bridge

has a width of up to 14.8m

with footpaths of 4.5m oneither side. Each span is

made up of 11 simply

supported longitudinal hog

back symmetrical cast iron

beams spaced

approximately 1.8m apart

and two outer simply

supported asymmetric cast

iron beams. Between the

beams there are

transversely spanning

shallow masonry jackarches in all but two bays of 

each span. The other bays

are formed by cast iron

deck plates

accommodating large

service pipes. Trial holes

during the assessment

stage found a large

number of services,

ranging from small traffic

power cables, through

banks of communications

fibre optics to large

diameter (c. 21") high

pressure water and gas

mains. The deck plates

have cast-in perpendicular 

and diagonal downstand

stiffening ribs and therefore

do not present a flat soffit.

Previous assessment of 

the structure had shown

the internal girders to have

7.5T ALL capacity, but the

external girders were at fullcapacity under dead load

alone, and the deck plates

could only withstand 3T

 ALL.

 A number of options were

considered at the feasibility

stage, including reducing

the spans, dead load

reduction by foamed or 

lightweight concrete and

thinner surfacing, post-tensioning of the girders,

reconstruction, and

unstressed CFRP plate

bonding to the girders and

deck plates. The recommended option was CFRP

strengthening with some dead load reduction, based on

minimal disruption to the highway network, railway

network, and statutory services, and the lowest cost

estimate of approximately £1.5m excluding possession-

related costs such as possession management, provision

of safety related personnel etc.. Reconstruction in this

instance was simply not

feasible due to the existenceof numerous services,

possession availability and

the important nature of the

highway thoroughfare.

Currently, the span over the

disused siding has been

strengthened during daytime

hours, and the span over the

London Underground

District Line has been

strengthened during a 52 hr possession at Christmas

and New Year 2004/5 for the

girders and part of the deck

plates, and a 52 hr 

possession in July 2005 to

complete strengthening of 

the deck plates (Figures 5

and 6). In addition, topside

works have been undertaken

including reinstatement with

lightweight concrete,

waterproofing and re-

surfacing. Strengthening of 

the main span is pending the

availability of a suitable

possession on the Network

Rail WLL, possibly in

2007/8. The current cost of 

the scheme is £2.5m

including all possession-

related costs.

Maintenance inspections to

the strengthened spans

have shown no deteriorationto the CFRP strengthening.

Paper 14Recent Developments in Strengthening Technology and the Strengthening/Reconstruction Decision

Figure 4 - Hammersmith Road overbridge (A315)

Figure 5 - Strengthening of girders using CFRP plates

Figure 6 - Strengthening of deck plates using CFRPcruciforms and plates

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Railway Bridges - Today and Tomorrow 111

Paper 14 Recent Developments in Strengthening Technology and the Strengthening/Reconstruction Decision

Figure 7 - Procedure for implementation of FRP composite strengthening technology onto Network Rail infrastructure

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112 Railway Bridges - Today and Tomorrow

Discussion of FRP Strengthening Issues

The case studies described previously show the various

stages in the complete design process (from initial advice

to installation and finally in-service maintenance). These

stages are defined more rigorously in Figure 7. From the

experience gained from all the FRP strengthening

schemes on Network Rail infrastructure, and also other 

infrastructure, a number of factors are clearly favourablefor the feasibility of a FRP strengthening scheme. These

include:

i) Presence of services. Where a large number of 

services are present, any strengthening options

requiring invasive works near services, or reconstruction

options, become less feasible due to the risk of damage

to the services and cost of diversion.

ii) Requirement for continuous trafficking. FRP

strengthening can typically be undertaken under single

lane running, occasionally with short road closures (nomore than 1 day). Other strengthening methods, and

reconstruction, often require full road closures of the

order of weeks.

iii) Cast iron substrate. Bolting and drilling into cast iron

is generally not recommended, which leaves bonding

and clamping as acceptable fixing methods.

Furthermore, the assessment of cast iron is essentially

based on linear elastic principles; the higher the modulus

of a bonded strengthening material, the greater its

strengthening effect. This means that UHM CFRP

composite materials are very effective.

iv) Assessed capacity. There is a limit to a structure

being strengthened with FRP materials, which varies

with the type of substrate and assessment or design

philosophy. However, where the assessed capacity is

greater than 3 to 7.5T ALL, unstressed FRP

strengthening is usually technically feasible and cost

effective. Where the assessed capacity is less than this,

some form of dead load mobilisation is usually required

(e.g. prestressing, jacking or large-scale reinstatement

of fill with lightweight material).

v) Possession length. FRP strengthening can typicallybe undertaken within rule-of-the-route overnight

possessions, and therefore has a lesser requirement for 

long possessions (although in some cases it may still be

more efficient to undertake the FRP strengthening in a

long possession).

vi) Interested parties. Where a large number of parties

have a serious interest in a scheme, less intrusive

strengthening methods tend to be more conducive to

achieving overall approval. FRP strengthening has

minimal visual impact to a structure, and usually the

structure is not in a temporarily weakened state duringFRP strengthening, as may occur for other strengthening

methods.

 As well as being cost effective, FRP strengthening methods

usually minimise disruption to both the railway and highway

network (for overbridges). This has an effect on the successful

development of any strengthening scheme, due to the need

for liaison and acceptable solutions for both Network Rail and

the local authority. In many cases, where a solution has

otherwise been difficult to find that is acceptable to all

concerned parties, FRP strengthening has been the only

viable solution.

FRP New-Build Technology

In the past 25 years, and particularly in the last decade,

advances have been made in the use of FRP composites for 

new and replacement structures, and structural components

in general. Approximately 150 footbridges, and 100 vehicular 

bridges, constructed using FRP composites, have now been

installed worldwide. FRP composites have also been used

in offshore and industrial applications for walkways and

parapets, in aerospace and marine applications for 

secondary and primary structural components.

Recent significant uses of FRP composites for new-build

include Halgavor footbridge over the A30, West Mill vehicular 

bridge in Oxfordshire, and Mount Pleasant Occupation

bridge over the M6 in Lancashire (Figure 8), and various

station footbridges (Figure 9).

Paper 14Recent Developments in Strengthening Technology and the Strengthening/Reconstruction Decision

Figure 8 - Mount Pleasant FRP bridge during load testing

Figure 9 - Kosino station footbridge, Russia

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Consultants are currently reporting to Network Rail on the

implications of FRP composites for structural components

and new-build on the railway infrastructure, including

footbridges, overbridges, underbridges, platforms and

platform canopies, and other structures. The main

benefits to be gained in using FRP composites for new-

build are:

i) Greater durability and minimal maintenance. This alsohas a follow-on impact as it reduces costly and disruptive

maintenance works on the railway.

ii) Simple and quick installation due to the pre-fabricated

and lightweight nature of FRP composite structures.

iii) For overbridges, minimal road closures are required

due to the ability to have all bridge furniture, including

surfacing and parapets, pre-installed on the structure

which can then be craned in.

Currently, the business case for FRP compositefootbridges is favourable on capital cost, and becomes

very competitive when whole life costs are included. The

case for vehicular bridges is less clear, although likely to

improve in the near future; the benefits of using an FRP

composite structure would need to be considered on a

project-specific basis, being particularly favourable where

disruption to the railway and highway are critical.

Currently, an all-FRP composite sidebridge is under 

design in LNE territory (Form A stage) to replace a

wrought iron girder/jack-arch structure over a canal.

 Additionally, there is great scope for the use of FRP

decking systems for re-decking of masonry arches and

girder/jack-arch type structures, where a pre-surfaced

FRP composite deck acts to reduce dead load in addition

to strengthening.

The use of FRP composites for building-type components

(e.g. platforms, platform canopies etc.) generally has a

longer track record than for bridges, and there appear to

be no barriers to these applications; indeed, a number of 

secondary or non-structural FRP components are already

being used on the railway infrastructure, such as

stairways and parapets to signal boxes, walkways and

handrails retro-fitted to existing bridges and stair treadreplacements.

Summary

The approach taken by Network Rail in using FRP

strengthening methods on their infrastructure has

provided a number of benefits:

i) Cost savings over other strengthening

methods/reconstruction.

ii) Minimal disruption to the railway and highway

network.

iii) Control of risk by only allowing FRP strengthening

where there is sufficient knowledge and design

guidance, designed and checked by experts, and

critically reviewed after each installation. This enables

best practice to be quickly developed for the benefit of 

Network Rail (and other infrastructure owners).

The total cost saving achieved currently to Network Rail,

accrued due to the use of FRP strengthening over other strengthening/reconstruction methods to 13 structures, is

approximately £5m. The cost saving for any particular 

structure has ranged from marginal (for concrete

structures where steel plate bonding may also be feasible,

albeit with practical and durability issues) to over £1m

(where the bridge has numerous services and

reconstruction is the only other option).

The use of FRP composites for new-build, reconstruction,

on the railway infrastructure is likely to provide cost

benefits, as well as less disruption to both the railway and

highway, benefiting Network Rail, local authorities and the

public alike.

 Acknowledgements

The views expressed in the paper are those of the authors

and not necessarily those of Network Rail, Mouchel

Parkman or Tony Gee and Partners.

Paper 14 Recent Developments in Strengthening Technology and the Strengthening/Reconstruction Decision

Railway Bridges - Today and Tomorrow 113

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Notes

114 Railway Bridges - Today and Tomorrow

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115Railway Bridges - Today and Tomorrow

The material used in this publication is Revive Silk, manufactured by a

paper mill with ISO 40001 accreditation. The material is fully recyclable

and biodegradeable, and meets the National Association of Paper Merchants (NAPM) recycling standards.

Revive Silk is made from a minimum of 75% post-consumer waste, the

remaining 25% being mill broke virgin fibres. The virgin fibre is totally

chlorine free.

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