overview of bridge design and construction

Overview of Bridge Design and Construction

Dr. Lakshmy Parameswaran

Chief Scientist

Bridges & Structures Division,

CSIR-CRRI, New Delhi-110 025

11/28/2013 1Bridge Design & Construction

Contents

• Bridges – Definition

• History of Bridge Construction

• Type of Bridges

• Criteria for selection of bridge type

• Bridge Components

• Design and Construction Aspects


Bridge-Definition

• Any structure to cross-over an obstruction like river, canal, railway line and another road

• It carries a roadway or a rail across natural/artificial obstacles

• Essential for free flow of transport

• Vital Link in Transportation system


Bridges Control the Capacity of Transportation System

If the width of a bridge is insufficient to carry thenumber of lanes required to handle the trafficvolume, the bridge will be a constriction to theflow of traffic.

If the bridge is deficient and unable to carry heavytrucks, load limits will be posted and truck trafficwill be rerouted.


Highest Cost

• Bridges are expensive in comparison toapproach roads.

• As a bridge is the key element in atransportation system, balance must beachieved between handling future trafficvolume and loads and the cost of heavier andwider bridge structure


If Bridge Fails the Transoport System fails

• The importance of a Bridge can be visualized by considering the comparison between the two main components of a highway system i.e. a road and bridge itself.


History of Bridge Construction

Roman Arch Bridge, 100BC

wooden planks, Stone,

Cast Iron Bridge,1800AD

Arch Bridge in China 700AD

Wrought Iron Bridge, 1850AD

Suspension Bridge, 1920 AD

Cable stayed bridge

PSC girder bridge

Integral Bridge

Extrados Bridge


Classification of Bridges

• Material – Timber, Stone, Concrete, Steel, Composite, FRP

• Usage – Pedestrian, Highway, Railway, Pipeline

• Span - Small, Minor, Major, Long

• Structural Arrangement

• Structural form

• Supports

• Plan Geometry


Classification According to Structural Arrangement

• The classification of the bridge types can also be according to the location of the main structure elements relative to the deck, as follows:

• Main Structure Below the Deck Line

• Main Structure Above the Deck Line

• Main Structure coincides with the Deck Line


Different Structural Arrangement

Through Bridge Underslung Bridge


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Classification Of Bridge

Structural Form

• Arch Bridges

• Slab Bridges

• Slab Girder Bridges

• Box Girder Bridges

• Plate girder/truss

• Cable Stayed Bridges

• Suspension Bridges

Supports • Simply supported

• Continuous

• Balanced Cantilever

• Integral

Plan Geometry• Straight

• Curved

• Skew

Structural Actions Differ and Understanding Important 11/28/2013 Bridge Design & Construction

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Type of Highway Bridges

Span Range Type of Construction<6m Culverts

>6m <10m Solid RCC Slabs

>10m <20m Precast/ Pretensioned or

Post tensioned beams,

RCC beams

>20m<25m RCC voided slab

>25m<30m PSC Voided slab

>30m<35m RCC Box

>35m<40m PSC Beams

>40m<55m PSC box

>55m<120m Cantilever /segmental

Construction

>120m<1000m Cable stayed

>800m <2000m Suspension Bridge 11/28/2013 Bridge Design & Construction

Classification of Bridge as per IRC:5Minor Bridge:A Minor bridge is a bridge having a total length up to 60m.Major Bridge - Total Length >60mA small bridge on rural road could be generallytaken as a bridge of total length between6m and 30m and individual span not more than 10m

Between 6 and 30 m

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Multi-span Simply Supported Bridge

Continuous Bridge

Classification of Bridge Based on Support Condition

11/28/2013 Bridge Design & Construction

Balanced Cantilever Bridge -Ganga Bridge, Varanasi11/28/2013 15Bridge Design & Construction

16

Classification based on Plan Geometry-

CURVED BRIDGES

In Addition to M & S, Torsional Moments DevelopThroughout even Under Symmetrical Loading, Magnitudedepends on e and R

Moments in Outer Girders much Larger than in InnerGirders, 'Developed' Length Analysis inaccurate

High Centrifugal Forces on Bearing System andPiers/Abutments

Behaviour Different Than Straight Bridges


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SKEWED BRIDGES

Behaviour Depends on Span, Roadway Width &

< 200 , Behaviour same as for Straight Bridge

> 200, Moments mx , my , Torsional Moments mxy

Behaviour Complex if Bridge X-Section is Cellular

Skew Bridges

Skew Angle

Water Flow

Edge Beam

(a) Skew Bridge

(a) Skew Bridge, Span<

Road Width


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Criteria For Selection of Bridge Type

• Geometric condition of the site

• Subsoil condition of the site

• Functional Requirements

• Construction and Erection consideration

• Ease of Maintenance

• Regulatory Issues

• Aesthetics

• Economics


Geometric Considerations at Bridge Site

• Horizontal and vertical alignment of highway route ( Eg. Road on curve- Choose continuous box girder- easily built, high torsional rigidity)

• Clearances above and below the roadway

• Long span bridges with tall piers over navigable spans will require different bridge type than with medium span

• Handling of traffic during construction is decided based on geometry at bridge site.


Sub-soil condition at bridge site

• Bearing capacity of founding strata &its level decides the type of foundation for piers/abutments

• Location & extent of soft soil layers, Possibility of differential settlement

• Water table level, quality of water

• Drainage condition on the surface and below the ground - affects the earth pressure, stability of cuts &fills, movement of embankment

• Seismicity of the site, possibility of liquefaction of soil

• Type of rocks, faults/ fissures11/28/2013 20Bridge Design & Construction

Functional Requirements

• Bridge should be able to carry present and future traffic

• Bridge over river should function even during flood

• Number of lanes, provision of footpath

• Bridge should not constrict the flow of water/debris

• Provision for future widening - Preference of multiple girder over concrete segmental bridge


Regulatory Issues

Regulations which are beyond the control of the Engineer

• Clearances for construction of bridge over Navigational water ways, railways, canals

• Environmental clearances• Clearances from agencies like ASI• Noise control Act• Protection of marine life, endangered species,

wild life etc.


Aesthetics in Bridge Design

•The conventional order of priorities in bridge design is safety, economy, serviceability, constructability, and aesthetics.

•The belief that improved appearance increases the cost ofbridges is not always correct and often the mostaesthetically pleasing bridge is also the least expensive.

•The additional cost is about 2% for short spans and only about 5% for long spans

•It is important that designers are aware of the qualities of a bridge that influence the perception of beauty


Economics

• Initial cost + Maintenance cost to be considered

• Bridge with minimum no. of spans, fewest expansion joints and widest spacing of girder will be economical

• Concrete bridge maintenance cost < steel bridge


25

Components of a Bridge

• Superstructure

• Substructure

• Foundation

• Bridge Appurtenances


26

Superstructure

COMPRISES OF ALL COMPONENTS OF A BRIDGE ABOVE THE SUPPORTS. BASIC SUPERSTRUCTURE COMPONENTS ARE

WEARING SURFACE – Portion of Deck surface which resists traffic wear

Eg. Bituminous or concrete

DECKPhysical extension of the roadway across the obstruction to be bridged.

Function of deck is to distribute loads along the bridge cross-section.

Consists of Primary members/main girders and Secondary member/cross-girder


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SUBSTRUCTURECONSISTS OF ALL ELEMENTS REQUIRED TO SUPPORT THE SUPERSTRUCTURE. BASIC SUBSTRUCTURE COMPONENTS ARE

ABUTMENT

PIER

BEARINGS

PEDESTALS-Short column on an abutment or pier which directly supports a superstructure main girder.

BACKWALL-Primary Component of abutment acting as a retaining structure at each approach.

WINGWALL-Sidewall to the abutment back wall designed to assist in confining earth behind the abutment


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Abutment• Earth retaining structures which support the

superstructure and roadway at the beginning and end of a bridge.

• Types

Spill Through

Slope Protected

Solid Abutment

Reinforced Earth

Materials Used

RCC, PCC, Brick Masonry, Stone Masonry

Reinforced Earth


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R.C.C Spill – Through Abutment with Fly- Back type Returns

P.C.C. Counterfort Abutment

Reinforced Earth Wall Abutment


30

PierStructures which support superstructure at the intermediate

point between the abutment.

* Based on MaterialMasonryPCC RCC Steel

* Based on GeometryWall type pier Single CircularSolid pier with Hammer Head Hollow pier rectangular/circular

Trestle Pier


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Solid Pier C/S R.C.C. Wall Type Pier

R.C.C Trestle PierSingle Circular Solid

R.C.C Pier with Hammer Head

Cellular R.C.C/PC.C. Concrete Pier

Hollow Circular R.C.C Pier


32

BEARINGS

• The Part of the Bridge Structure which bearsdirectly all the forces from the structureabove and transmits the same to thesupporting structure.


33

Functions of Bearings

(i) Transfer force from various parts of thesuperstructure components or from superstructure tosubstructure.

(ii) Permit longitudinal or transverse movements orrotation of one part with respect to other .

(iii) Allowing free movements in some directions butrestraining movements in some other directions.


34

Selection of Bearing

• Type of Material of Deck

• Geometric Shape of Bridge Deck in Plan

• Dimension of Bridge

• Movement of Bridge due to Thermal

Effects

• Seismic Performance

• Serviceability Requirements.


35

Forces Acting On Bearing

• Reactions

• Longitudinal Forces

• Transverse Force

• Uplift Force


36

Type of Bearings

• Stone, Non-metallic Materials, Concrete, Metallic Plate & Elastomeric Pad &Strip

• Steel Bearings

• Elastomeric Bearings

• Composite Bearings

• Spherical Knuckle Bearings

• Pot Bearing

• Hinge Bearing for Cantilver Spans

• Bearings For Seismic Protection


37

Sliding movement is permitted between two surfaces

Used In Bridges with span less than about 15m

Sliding Bearing


38

ROCKER BEARING (TYPICAL)

Pinned Bearing used for span More than 15m


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ROLLER –CUM-ROCKER BEARING (TYPICAL)( Useful in 15m to 35m span)11/28/2013 Bridge Design & Construction

ROCKER & ROLLER BEARINGS


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Elastomeric Bearing

• An elasomeric bearing can consists of unreinforcedelastomeric pad or reinforced elastomeric bearing.

• Reinforced elastomeric bearing-bonding of alternatelaminates of rubber and steel.

• Under the load, elastomeric material will tend to deform orbulge which is restricted with steel plates

• No moving parts.• For Spans 7.5 to 15m Plain elastomeric pads could be used.• Reinforced/laminated bearing Useful in 15m to 35m span

range. However to be avoided in seismic Prone areas or usewith seismic attachment.

• Elastomeric Bearings Preferred in Submersible Bearing.


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View Of Elastomeric Bearing11/28/2013 Bridge Design & Construction

•Creating shadow becomes especially important with the use of solid concrete safety barriers that make the girders look deeper than they actually are.

•Shadows can be accomplished by cantilevering the deck beyond the exterior girder.

•The effect of shadow on a box girder is further improved by sloping the side of the girder inward.

Light and ShadowBox- Girder

Bearing

Pier cap11/28/2013 43Bridge Design & Construction

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Characteristics of Bearing

Bearing Type Range (kN)

• Sliding Plate 1000

• Steel Roller (Single) 3000

• Steel Roller (Multiple) 10 000

cum Rocker

• Steel Rocker 10 000

• Steel Cylindrical Knuckle 10 000

• Steel Spherical Knuckle 10 000


45

Characteristics of Bearings

Bearing Type Range (kN)

• Steel Pot with Confined 25 000

Elastomer

• Stainless Steel-PTFE Sliding 25 000

• Guide Bearing (For Horizontal Force) 1 000


46

Performance Life of Bearing

Life of bearing depends on quality of materialused to manufacture, environment,maintenance etc.

Elastomeric bearing up to 20-25 Years

Composite Bearings up to 50 years

Steel bearings-100 Years


Expansion Joints

To cater for expansion and contraction of Bridgesuper structure

Joint should be leak proof so that thesuperstructure, bearings and piers do not getdamaged due to leakage of rainwater


Expansion Joints for Small Span Bridges

Copper Plate Expansion Joints up to 25mm gap

Sliding M.S Plate expansion Joints

Joint develops cracks in the bituminous wearing coat andduring rainy season gets deteriorated.


Buried JointBuried Joint shall consist of continuously laid bituminous surfacingover the joint gap bridged by a steel plate resting freely over thetop surface of the deck of concrete.

The width of gap shall be kept as 20mm

Steel plate shall conform to Weldable structural steel –IS 2062.The plate shall be 12mm thk and 200mm wide.The plate shall be made of minimum no. of pieces, i.e not more than 2 pieces per traffic line width.8mm dia. 100mm long nails spaced at 300mm c/c along centreline of plate shall be welded to the bottom surface of the steelplate to protrude vertically into the joint gap in order to preventdislodging of plate.


Asphaltic Plug JointAsphaltic plug joint shall consists of a ploymer modifiedbituminous binder, carefully selected single sizeaggregate, bridging metallic plate and heat resistantfoam caulking/backer rod.It shall cater for a horizontal movement of 25mm andvertical movement of 2mm.The minimum width of the joint shall be 500mm andmaximum width shall be 750mm.Minimum depth shall be 75mm and maximum depth<100mmThe joint works satisfactorily within temperature range-5 to +50degC.


COMPRESSION SEAL JOINTS

•Seals are –perforated

closed-cell plastic or

hollow neoprene shape

•Performance depends

upon material


STRIP SEAL JOINTS

•Better than

compression seal

joints

•Strip seal is

mechanically locked

into a pair of rolled

steel

•Strip seal can

function in

compression and

tension


FINGER PLATE TYPE

•Used in medium and long

span bridges for some time

•Made from two loosely

interlocked cantilevering steel

plates

•Performance of these joints

can be enhanced by limiting

the size of openings on finger

plates to permit the safe

operation of narrow- tired

vehicles

•Debris creates problems


Expansion JointsDesigned to accommodate long. Movement/rotation

• Buried Joints/Filler Joints ≤10mm

• Asphaltic Plug Joints ≤ 25mm

• Compression Seal ≤ 40mm

• Single Strip/box seal ≤ 80mm

• Reinforced Elastomeric ≤ 80mm

• Modular Joints ≥ 80mm

• Finger Joints ≥ 80mm

• Reinforced Coupled Elastomeric - up to 230mm


Suitability Criteria for Adoption of Different Types of Expansion Joints

No Type Criteria Service Life Special Consideration

1 Buried Simply Supported Spans up to 10mm

10years Only for decks with bituminous asphaltic wearing coat. Steel plates may need replacement.

2 Filler Joint Fixed end of simplysupported spans with in significant movement

10years The sealant and joint filler would need replacement if found damaged

3 Asphaltic Plug Joint

Simply Supported spans for right or skew spans up to 20deg moderately curved or wide deck with maximum movement < 25mm

10years Only for decks with bituminous wearing coat. Not suitable for bridge with long. Gradient >2% and cross camber/super-elevation exceeding 3%. Not Suitable for curved spans and resting on yielding supports.


Suitability Criteria for Adoption of Expansion Joints

No

Type Criteria Service Life

Special Consideration

4 Compressionseal

Simply Support of continuous Spans right or skew (up to 30deg) moderately curved with maximum horizontal movement < 40mm

10years Chloropene /closed foam seal may need replacement during service

5 Elastomeric slab seal

Simply supported or continuous spans right or skew (<70deg) moderately curved with maximum horizontal movement up to 50mm

10years Not suitable for bridges located in heavy rain fall areas and spans resting on yielding support

6 Simple Strip seal joint

Moderate to large simply supported (cantilever) continuous bridge construction having right, skew or curved deck with movement > 70mm

25years Elastomeric seal may need replacement


No

Type Criteria Service Life Special Consideration

7 Modular strip/box seal

Large to very large continuous/ cantilever construction with right/skew or curved deck having maximum horizontal movement > 70mm

25years Elastomeric seal may need replacement during service

8 SpecialJoints for special condition

For bridge having wide deck/span length of more than 120m, or /and involving complex movement/ rotations in different directions /plan, provision of special type of modular expansion joint sych as swivel joint may be made.

10years Elastomeric seal may need replacement during service. Provision of these joints may be made with prior Approval of competent authority.

Suitability Criteria


AppurtenancesEmbankment- A raised area of fill surrounding a

structural component eg. abutmentUnderdrain- A drainage conduit, usually placed in

back fill material to transport water away from substructure elements

Approach- Section of roadway immediately before or after the structure, approach slab-prevent settlement of approach pavement

Railings/Crash Barrier, lighting, signage etc


Approach Slab

• Approach Slab for entire formation width for length of3.5m behind abutment between returns.

APROACH SLAB


Foundation

Open Foundation

Well Foundation

Pile Foundation


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Shallow Foundation

Open Foundation( Isolated footing) is adopted :

For Bridge/Fly over foundation where ground is not liable to scourDepth of Foundation not exceeding 5mOverburden soil layer is up to 4m thickRatio of Embedment depth to Foundation width <0.5

Advantage- Simple, low cost (50 to 65% cost of deep foundation)

Raft Foundation is adopted for

Small and Minor bridges Small stream and river bridges Submersible bridge

Raft is Not Recommended for

Bridges Span more than 10m (Uneconomical)Stream having velocity more than 6m/secLarge flow of water/ standing water creates the dewatering difficult


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Well Foundation

Well foundations are Provided

To transmit large vertical and horizontal loads to deeper andstronger strata because of low bearing capacity of theoverlying soils.

To protect the foundation against scour, where it isnecessary.

Where open excavation becomes costly and uneconomicalas heavy timbering has to be provided.


Well Foundation(Also called Caisson, Pier or Monolith)

Bridge Pier

River bed level

Well cap

Well Steining

( RCC/ Masonary)

Sand Filling

Bottom Plug

Cutting Edge

River Water

Overburden Soil

Rock11/28/2013 63Bridge Design & Construction

Well Construction

•Casting of well kerb (cutting edge )

•Extending the height of steining

•Soil excavation within the well pockets

(mostly underwater with a grab)

•Well Sinking (self weight, anchors,water jetting, compressed air jetting at kerb)

•Bentonite slurry stabilsation of gap

•Checking verticality and correcting the tilt

•Construction of bottom plug


65

Pile FoundationWhen the soil strata below the ground surface is highly

compressible and too weak to support the load transmittedby the superstructure.

When the plan of the structure is irregular relative to itsoutline and load distribution. In such cases, pile foundationis required to reduce the differential settlement.

To withstand the horizontal forces by bending, while stillsupporting the vertical load transmitted by thesuperstructure. This type of situation is generallyencountered in bridges likely to be subjected to high windand/or earthquake forces.

If Expansive and collapsible soils encountered at the site ofa proposed Bridge, Pile Foundations may be used in whichpiles are extended into stable soil layers beyond the zone ofpossible moist change.

Soil susceptible to seismically induced liquefaction11/28/2013 Bridge Design & Construction

67

• IRC:5-1998: General Features of Design

• IRC :6-2010: Load and Stresses

• IRC:112-2011: Code of Practice for Concrete Road Bridges

• IRC:22: Design Criteria for Composite construction

• IRC 24: Design Criteria for Steel bridges

• IRC-78: Foundation and Substructure

• IRC-45: Design of Well Foundation in Sandy Strata

• IRC-83(Part I)-1999-Metallic Bearing

• IRC-83(Part II)-1999-Elastomeric Bearing

• IRC-83(part III)-2002-Pot,Pot-cum-PTFE, Pin and MettalicGuide Bearing

IRC Code of Practices for Design of Bridges

SPECIAL PUBLICATIONS for BRIDGE DESIGN

• IRC: SP:64-2005- Guidelines for the Analysis and Design of Cast-in Place Voided slab superstructure

• IRC SP: 65-2005- Guidelines for Design and Construction of Segmental Bridges

• IRC: SP:66-2005- Guidelines for Design of Continuous Bridges

• IRC: SP:67-2005 Guidelines for Use of External and Unbonded Prestressing Tendons in Bridge Structures

• IRC: SP:69 Guidelines and Specifications for Expansion Joints

• IRC SP:70-2005 Guidelines for Use of High Performance Concrete in Bridges

• IRC:SP:71-2005 Guidelines for Design and Construction of Pretensioned Girder Bridges

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Quality Control

• Guidelines on Quality Systems for Road Bridges : IRC SP-47 1998

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Specifications

Guidelines for the Design of Small Bridges and Culverts - IRC: SP: 13(2004)

Rural Roads Manual- IRC:SP:20

Specifications for Rural Roads- Ministry of Rural Development, Published by IRC

70

Planning of Bridges

• Traffic Survey

• Topographical Survey

• Hydrological Survey

• Geotechnical Investigation

• Environmental Considerations

• Functional Requirement

• Span Arrangement & Bridge Type Selection

• Economic Feasibility


Highway Bridge Loads

• Permanent- Dead load- Load induced due to creep and Shrinkage• Transient- Traffic- Environmental- Construction Loads


Orthotropic Plate Theory Stiffness Approach

Theory Design

curves

Finite

Difference

Folded

Plate

FEM Finite

Strip

Grillage Space

Frame

(A) Type of Deck

Solid Slab

Pseudo Slab

Slab & beam

Cellular +

Composite

( B) Plan Geometry (+very Limited Applicability)

Right

Skew > 20 o

Curved

Arbitrary

C Support Conditions

Simply Supported

Continuous

Arbitrary

Table : Applicability of Methods of Analysis

Source : Bridge Deck Analysis, Cusens & Pama 11/28/2013 73Bridge Design & Construction

Limitation of Working Stress Design Approach

Working Stress Method

• Stresses in a Bridge Caused by DesignLoads are Compared with AllowableStresses.

• Allowable stresses are increased forunusual loads like wind and earthquakeso that all loads have same factor ofsafety.


Need for Limit State Design

•Loads acting on Bridges and resistance ofComponents are random in nature.•Working Stress Method Does not Account theVariability of loads acting on a structure and strengthof its components.

•Limit State Design Approach was Introduced in 1970’s for design of Concrete Structures.


Limit State Design

Limit States are boundaries Between Safety andFailure

Two Types of Limit States

-Ultimate Limit States-Related to Capacity of Structuralcomponent in flexure, shear, torsion & stability.

-Serviceability Limit States- Related to Fatigue, cracking,deflection and vibration of structural components –associatedwith gradual deterioration, users discomfort, andmaintenance cost.


Construction & Erection Aspects

• Time required to construct a bridge depends on the bridge type ( precast vs cast-in-situ)

• Larger precast members - shorter the construction time

• Larger the precast members - Difficult to lift and transport

• Availability of material for construction

• Skilled labour


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Methodology

The superstructure of bridges is builtfrom one or more piers by means offormwork carriers with the cantileveringmethod.

Structure advances from a short stub ontop of a pier symmetrically in segmentsof about 3 m to 5 m length

Application

Suitable for medium and longspan concrete bridges

Recommended especially wherea scaffolding is difficult orimpossible to erect as e.g., overdeep valleys, wide rivers, trafficyards or in case of expensivefoundation conditions forscaffolds

Balanced Cantilever Bridge Construction


79

Methodology

The sections are cast continuously, oneafter another, and are then stressedtogether.

The superstructure, growing section bysection is launched over temporarysliding bearings on the piers until thebridge is completed.

15 m to 30 m long sections of the bridgesuperstructure in a stationary formworkis cast behind an abutment to push acompleted section forward with jacksalong the bridge axis

Application

Suitable for the construction ofcontinuous post-tensioned multi-spanbridges

Limitations

Spans should not exceed 60 m approx.and the bridge sections must beconstant.

Superstructure of the bridge has to becontinuous over the whole length andstraight or have a constant curvature inplan and elevation

Incremental Launching Bridge Construction


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Methodology

The launching girder itself isnormally a steel structure withrather sophisticated equipment,moving forward on the bridgepiers span by span.

Application

Suitable for multi-span bridgesover difficult terrain or waterwhere scaffoldings are expensiveor not feasible at all

Can handle cast-in placeconcrete, as well as prefabricatedelements.

Launching girders are most oftenused for placing prefabsegments, match-cast andstressed together, or completeunits spanning from pier to pier.

Launching Truss Bridge Construction


overview of bridge design and construction

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