over-conservatism in de~ign- ;

I

by G B Card (Frank Graham Consulting Engineers Limited)and P Darley (TRL)

Project— Anexectiive age~ of

diTHE DEPARTMENTOF TRANSPORT

Report 120E455NBG

ABO~ ~L

The TransportResearchLaboratoryisanTransport.Itprovidestechnicalhelpand

executiveagencyoftheDepartmentofadvicebasedon researchtoenablethe

Government-to setstandardsfor-highway and vehicledesign,to formulatepolicieson road safety,transportand theenvironment,and to encouragegoodtrafficengineeringpractice.

TRL alsosellsitsservices,actingas contractor,consultantor providingfacilitiesand staffon a fee-payingbasisforcustomersintheprivatesector,

TRUS expertiserangesfrom theconstructionofhighways,bridgesand tunnels,toallformsofroadsafety,trafficcontroland driverbehaviour.

For instance,highways and structuresresearchat TRL develops improvedmaterialsand methods which enable earthworks,roads and bridgesto bedesigned,builtand maintainedmore cost-effectively.New ways of reinforcingearthcan cut constructioncosts,while bridgescan be modified to reducecorrosion.Road surfacesdevelopedatTRL can reducenoiseand cutwet-weatherroadsprayfromlorriesby 90percent.

Safetyresearchvariesfrom monitoringtheincidenceofdrinkingand drivinganddevisingways ofreducingit,toimprovingjunctiondesignsand cooperatingwithEuropeanpartnerson new standardsforimproved impactprotectioninvehicles.

Trafficresearchseeks to make the most of existingroads by, for instance,improvingtrafficsignalcoordinationand devisingsystemswhich help driversavoidcongestion.Other researchlooksattheeffectivenessof parkingcontrolsand improvedcrossingsforpedestrians.

TRL researchalsoinformsGovernment transportpolicyby studying,forexample,theeffectsofbus deregulationand how landuseinteractswiththeroad and railtransportsystem.

TRL employs around 600scientists,engineersand supportstaff.Itsheadquartersare at Crowthorne,Berkshirewhere itsfacilitiesincludea 3.8km testtrack,astructureshallwhere bridgestructurescanbe stressedtobreakingpoint,a facilityforcarryingout acceleratedtestson road structures,and advanced computersystemswhich are used to develop trafficcontrolprograms.TRL Scotlandissituatedin Livingston,near Edinburgh,where the staffare concernedmainlywithresearchand advisorywork inthefieldsofground engineering,bridgesandroadpavements.ThisunithasresponsibilityforallTRL work inScotland.

A largeproportionof theresearchissub-contractedtoindustry,consultantsanduniversities.The Laboratoryalsocollaborateswith localauthoritiesand otherorganisationswithin Europe and elsewhere.In addition,TRL expertiseisprovidedtodevelopingcountriesaspartofBritain’soverseasaidprogramme.

Formore information:TRL PublicRelations,0344770587

TRANSPORTRESEARCH LABORATORYAn Executive Agency of the Depaflment of Transpoti +~~~

—

PROJECT REPORT 120‘~*L TWNSWRT RESEARCHUBORATORY

LIBRARYSERVICES

ASSESSMENT OF SUBSTRUCTURES ANDOVER-CONSERVATISM IN DESIGN

by G B Card (Frankand P Darley ~RL)

Graham Consulting Engineers Limited)

Prepared for: Project Record: E455NBG Assessment of Substructuresand Foundations”

Customer: Bridges Engineering Division, DOT

CopyrightControllerof HMSO 1995. The views expressedinthis publicationare not necessarilythose of theDepartment of Transpoti.

Civil Engineering Resource CentreTranspofl Research LaboratoryCroMhorne, Berkshire, RG11 6AU1995

ISSN 0968-4093

Executive Summary

Symbols and Abbreviations

Abstract

1.

2.

3.

4.

5.

6.

7.

8.

9.

INTRODUCTION

ASSESSMENT PROCED~ES

APPRAISAL TO ASSESSMENT STANDARDS

3.1 Methodology

3.2 Data Collection and Processing

3.3 Assessment Calculations

FINDINGS FROM ASSESSMENT APPRAISAL

4.1 Ultimate limit state

4.1.1 Resistance to sliding (ULS)

4.1.2 Bearing pressure (ULS)

4.1.3 Wall moments (ULS)

4.1.4 Wall shear (ULS)

4.1.5 Base and punching shear

4.2 Serviceability limit state

ULS )

4.2.2 Allowable bearing pressure (SLS)

4.2.3 Wall moments (SLS)

APPRAISAL TO DESIGN STANDARDS

FINDINGS FROM DESIGN APPRAISAL

6.1 Ultimate limit state

6.1.1 Resistance to sliding (ULS)

6.1.2 Bearing pressure (ULS)

6.1.3 Wall moments (ULS)

6.1.4 Wall shear (ULS)

6.1.5 Base and punching shear (ULS)

6.2 Serviceability limit state

6.2.1 Allowable bearing pressure (SLS)

6.2.2 Wall moments (SLS)

SOIL STRENGTH PARAMETRIC STUDY

CONCLUSIONS

AC~OWLEDGEMENTS

10. REFERENCES

APPENDIX A. Summary information sheet

APPENDIX B. Assessment worksheets

APPENDIX C. Example assessment: retaining wall

APPENDIX D. Example assessment: bridge abutment

APPENDIX E. Design worksheets

EXECUTIVE S~YSince the start of the current Bridge Assessment andStrengthening Programme, difficulties have been faced byengineers in respect of assessing substructures~ foundations andretaining walls when using the Design Manual for Roads andBridges (D~B, 1993). In addition changes in structural designrequirements have taken place as a result of revisions tostructural codes and changes in loading requirements asimplemented by Departmental Standards contained in the D~.Generally these changes have been developed for the assessmentand design of superstructures rather than substructures. Forthese reasons the effect of these changes and their applicabilityto the assessment of existing substructures has not beenconsidered in any great detail to date.

The report presents the findings of an appraisal of 25 existingreinforced concrete bridge abutments and retaining walls. Thesesubstructures were, in most cases, designed more than a decadeago on the basis of standards and codes which have now beensuperseded or revised. A quantitative appraisal of the adequacyof these substructures has been carried out based on currentassessment and design procedures given in Departmental Standardsand Advice Notes.

The findings of the appraisal indicate that the majority of thesubstructures are more than adequate under current assessment anddesign loads with high factors of safety for the limit stateconditions investigated. Some substructures are inadequate withrespect to specific limit state conditions as detailed in thereport, particularly in the case of the ultimate limit statecondition of the soil for sliding and bearing pressure. Themagnitude of loads and earth pressures acting on thesubstructures, used in the assessment and design calculations,would appear to be significantly lower than that adopted in theoriginal designs. This appears to be due to the fact that manyof the substructures were originally designed using loads andearth pressures derived using partial and material factors andload combinations appropriate for the design of the equivalentsuperstructure. This has led to an over-estimate of the loadsand pressures on the substructures analysed. In particular thishas resulted in unduly high lateral pressures on the structuralelements requiring larger reinforced concrete sections to providean adequate moment and shear resistance. Adopting earthpressures for the backfill (i.e. K, or KO) based on realistic soilstrength parameters and nominal dead and live loads for designor assessment, results in lower moments and shear forces and,hence, smaller structural sections.

The current Departmental Standards and Advice Notes for designand assessment are inconsistent in their guidance on the choiceof soil strength parameters and advocate either worst credibleor representative peak strength values. The findings of thea~~raisal hiqhlight the sensitivity of the assessment and designc;iculations- to ‘the choice ofThis has a significant effectadequacy of the substructures.

soil strength parameters used.on the interpretation of the

S~OLS AND ABBR~IATIONS

ABUTMENT/STRUCT~E DIMENSIONSbf width of substructure base, m

WI length of substructure base, m

W2 width of base heel, m

tl thickness of wall at base of stem, m

tlt thickness of wall at top of stem, m

G thickness of base, m

hlti height from wall crest level to groundwater level at

ULS condition, m

hm depth from groundwater level to base of stem level at

ULS condition, m

hlsb height from wall crest level to groundwater level at

SLS condition, m

h2sb depth from groundwater level to base of stem level at

SLS condition, m

h height of wall stem, m

a angle of wall stem from the vertical axis, degrees

z depth of soil in front of wall, allowing for

unplanned excavation, m

Z* depth of shear key below base, m

DECK DIMENSIONS

w bridge deck width, m

L effective span of bridge deck, m

td effective depth of equivalent solid deck, m

nk number of carriageway lanes, No.

w~ width of individual lane, m

LWF lane width factor

MATERIAL PROPERTIES

Tcw density of concrete, kN/m3

7fti bulk density of retained fill, kN/m3

Td bulk density of foundation soil, kN/m3

LOADING DATA

wSm load due to retained fill surcharge above crest level

of wall, kN

w~~ factored (LWF) highway MA uniformly distributed live

load surcharge on retained fill, kN (kN/m2

retaining walls)

w- factored (LWF) highway ~ knife edge live load

surcharge on retained fill: but note that Ww is

unfactored for BD 21/83 assessment, kN (kN/m2 for

retaining walls)

wA~~ substructure dead load, kN

W*~~ effective total live load highway surcharge on

retained fill from Type HA and HB loads, kN (kN/m* for

retaining walls)

DECK LOADING ON SUBSTRUCT~E

WD dead load of bridge deck and surfacing, kN

WA highway live load of bridge deck, kN

EARTH PRESSURE BACKFILL

HATERIAL

fCu

Ymc

fy

~ms

f,‘

effective cohesion of fill, kN/m2

effective angle of friction of fill, degrees

active earth pressure coefficient of fill

earth pressure coefficient at rest of fill

passive earth pressure coefficient of fill

STRENGTH PROPERTIES

characteristic cube strength of concrete, kN/m2

partial safety factor for concrete strength

characteristic strength of reinforcement, kN/m2

partial safety factor for steel strength

factored strength of steel reinforcement, kN/m2

STRUCTURAL PROPERTIES

d~A~m effective depth of wall stem section to the tensile

reinforcement, mdl

STM effective depth of wall stem section to the

compression reinforcement, m

ASTLSM cross sectional area of tensile reinforcement in stem,m2

dNABASE effective depth of base section to the tensile

reinforcement, m

d‘MSE effective depth of base section to the

compression reinforcement, m

AST~~~ cross sectional area of tensile reinforcement in base,m2

SOIL PROPERTIES/SETTL~ENT OF THE FOUNDATION

Qti ultimate bearing capacity of foundation, kN/m2

Q- allowable bearing capacity of foundation, kN/m2

P probable settlement, mm

A worst tilt of foundation, tan (angle)~, effective angle of friction of soil, degreescl effective cohesion of soil, kN/m2

K~ active earth pressure coefficient of soil

$ti passive earth pressure coefficient of soil

SLIDING OF FO~ATION

LOAD vertical loading on foundation base, kN

BSE RSE resisting shear stress on base, kN/m2

RES SLD sliding resistance, kN

SLD FCE sliding force, kN

FOS factor of safety

BEARING PRESS~E

FDN PRSS foundation pressure, kN/m2

BENDING IN THE STW

M ultimate moment of resistance of concrete section at

base of wall stem, kN/m2

F1 overturning force acting above the water table, kN

F2 overturning force acting below the water table, kN

F~ resisting force due to depth of soil in front of the

wall stem, kN

M, moment due to sloping wall stem, kN/m2

L maximum moment acting on wall stem, kN/m2

SHEti STRESS IN THE ST~

v~~ ultimate shear resistance of concrete section, kN/m2

v KO shear stress in stem due to acting pressures based on

1.5 & distribution for backfill, kN/m2

v K, shear stress in stem due to acting pressures based on

1.5 K, distribution for backfill, kN/m2

v~~~ shear stress in base beneath stem, kN/m2

vp~~ punching shear stress in base, kN/m2

ASSESSMENT OF SUBSTRUCTURES

ABSTRACT

A quantitative appraisal of the

OVER-CONSERVATISM IN DESIGN

adequacy of 25 reinforced

concrete bridge abutments and retaining walls has been carried

out using current assessment and design procedures given in

Departmental Standards and Advice Notes. These substructures

were, in most cases, designed more than a decade ago on the

basis of standards and codes which have now been superseded or

revised. The findings of the appraisal indicate that the

majority of the existing substructures are more than adequate

under the current assessment procedures with generally high

factors of safety for the ultimate and limit state conditions

investigated suggesting over conservatism in the original

design. Some substructures are inadequate with respect to

specific limit state conditions as detailed in the report,

particularly in the case of the ultimate limit state of the

soil for sliding and bearing pressure. Generally the abutments

and retaining walls, have adequate factors of safety for the

structural elements at ultimate and serviceability limit state

conditions. An exception to this is shear resistance of the

stem at ultimate limit state where many substructures are

inadequate. This is believed to be due to over-conservatism

in the current assessment and design standards. Tentative

conclusions to the likely reason for the apparent over-

conservatism in the design of the structural elements are

presented and recommendations given for modifications to

Departmental Standards and Advice Notes for the design of new

substructures.

1 INTRODUCTION

The current Bridge Assessment and Strengthening Programe, in

addition to superstructures, involves the assessment of bridge

substructures (abutments and wing walls including cantilevered

wing walls and skeletal abutments) , foundations, retaining

walls and buried structures. Since the start of the Programme

difficulties have been faced by engineers in respect of

assessing substructures, foundations and retaining walls when

using the Design Manual for Roads and Bridges (D=). This is

because the guidance is often of a general nature, qualitative

and sometimes conflicts with advice for both design and

assessment contained in other parts of the D~B as well as

British Standards.

1

In addition changes in structural design requirements have

taken place as a result of revisions to structural codes and

loading requirements as implemented by Departmental Standards

contained in the DB: Volume 1: Section 3: General Design.

Generally the revisions to structural codes and loading

requirements have been developed for the assessment and design

of superstructures rather than substructures. For this reason

the effect of these changes on the adequacy of existing

substructures, particularly structural elements, has not been

considered in any great detail.

To identify the effect of the changes in structural design

requirements an appraisal has been undertaken on 25 reinforced

concrete retaining walls and abutments constructed more than

10 years ago. These substructures were, in most cases,

designed on the basis of standards and codes which have now

been superseded or revised. A quantitative assessment of the

adequacy of these substructures has been carried out, in terms

of a factor of safety, for various limit state conditions.

An appraisal has also been carried out using current Design

Standards and Codes, as implemented by the D~B: Volume 1:

Section 3: General Design and Volume 2: Section 1:

Substructures, to establish the adequacy of the existing

substructures compared to current design practice.

The findings of this study will assist in formulating more

accurate and reliable guidance for the assessment of existing

substructures. In addition it will identify aspects in

current Departmental Standards and Advice Notes where

modifications can prevent over-conservatism in the design of

new substructures.

2 ASSESSMENT PROCED~ES

The general principle of the current Bridge Assessment and

Strengthening Programme is to determine, in terms of vehicle

loading, the load that a given structure will carry with a

reasonable probability that it will not suffer serious damage

so as to endanger any persons or property on or near the

structure under present day and future requirements. The

assessment includes both the superstructure as well as the

substructures.

Substructures are taken to represent all elements of the

2

bridge beneath the soffit of the deck, including bearings,

piers, bank seats, abutments, wing walls, piles and

foundations. In the case of arches the substructure includes

the springing and all elements beneath the ground. Retaining

walls are also classified as substructures.

The current assessment procedures are given in Departmental

Standards and Advice Notes contained in Volume 3, Section 4:

&sessment, of the D~ as follows:

Part 3 Departmental Standard BD 21/93: The assessment of

highway bridges and structures (supersedes BD

21/84) .

Part 4 Departmental Advice Note BA 16/93: The assessment of

highway bridges and structures.

Departmental Standard BD 34/90: Technical

requirements for the assessment and strengthening

for highway structures: Stage 1 - Older short span

bridges and retaining structures.

Departmental Standard BD 44/90: The assessment of

concrete highway bridges and structures.

Departmental Advice Note BA 34/90: Technical

requirements for the assessment and strengthening

for highway structures: Stage 1 - Older short span

bridges and retaining structures.

Departmental Advice Note BA 44/90:

44/90 - The assessment of concrete

structures.

Part 9 Departmental Advice Note BA 55/94:

bridge structures and foundations,

and buried structures.

The use of BD

bridges and

The assessment of

retaining walls

The

set

and

methodology used for the assessment of substructures is

out in BA 55/94 which summarises the relevant requirements

use of appropriate Departmental Standards and Advice

Notes. A flow chart is presented in Fig 1 which sets out the

logical sequence for the assessment procedure forsubstructures based on the use of BA 55/94 and relevant

3

Departmental Standards and Advice Notes. It also identifies

where there is a need to cross reference to British Standards

or other guidance documents.

In accordance with BD 21/93 and BA 16/93 the adequacy of a

substructure is initially determined from a visual inspection

of the general condition, including the significance of any

defects. This is because of the difficulty of access to all

parts of the substructure and also the complexity of assessing

the applied loadings. If inspection reveals; however, signs

of distress in the substructure and/or foundations Chapter 8

of BD 21/93 requires a quantitative assessment to be carried

out in order to ascertain a reduced safe level of loading.

There are, however, difficulties and ambiguities in carrying

out a quantitative assessment for substructures, as set out

below:

1. The general rules for assessment contained in BD 21/93

and other assessment related documents are primarily

intended for superstructures. Most of these rules are

less directly applicable to substructures associated with

soil-structure interaction.

2. In the absence of directly relevant Assessment Standards

calculations for substructures are based on Design

Standards given in the D~B: Volume 2: Sections 1 and 2,

as follows:

Section 1: Substructures.

Departmental Standard BD 30/87: Backfilled retaining

walls and bridge abutments.

Departmental Standard BD 32/88: Piled foundations.

Section 2: Special structures.

Departmental Standard BD 31/87: Buried concrete box

type structures.

These documents, as is expected from design standards,

contain conservative requirements.

3. In accordance with BS 8004: 1986 Foundations applied

4

loads to substructures and foundations should be nominal

loads (i.e. unfactored loads) since a lumped factor of

safety is applied to design soil strength parameters.

The relevance of partial load factors in accordance with

the Departmental Assessment Standards and Advice Notes

and their applicability to substructures is, therefore,

unclear in view of the requirements of BS 8004. This

ambiguity can lead to an over estimate of soil loading

and earth pressures acting on abutment and retaining

walls from the backfill.

4. BD 34/90 Clause 4.2 states that, when assessing

substructures, factors of safety used for design may not

be appropriate and relaxation from these should be

considered based on a realistic assessment of the soil

conditions. This guidance, however, is very subjective

and involves a decision by the engineer undertaking the

assessment. For example a decision to use worst credible

or representative peak soil strength parameters can

influence the choice of factors of safety to be adopted

for an assessment. In this context, worst credible soil

parameters are used consistently throughout this

appraisal in order to allow a direct comparison of the

effects of changes in structural requirements. The

significance of using factored soil strength parameters

is discussed in Section 7.

In view of the above, application of unmodified design rules

to assessments is likely to produce unduly pessimistic

estimates of load carrying capacity for substructures. In

addition it could potentially lead to different assessment

rules being used throughout the ~ and thus differences in the

interpretation of the adequacy of substructures.

3 APP~ISAL TO ASSESSMENT STAND~DS

3.1 METHODOLOGY

To identify the effect of changes and revisions of structural

codes and Departmental Standards and Advice Notes an appraisal

has been undertaken on a selectednumber of existing

reinforced concrete retaining walls and bridge abutments. The

substructures were, in some casesr designed more than a decade

ago on the basis of standards and codes which have now been

superseded or revised. All the substructures are reported to

5

be performing satisfactorily by the appropriate checking

Agent/Authority based on their visual inspection, undertaken

in accordance with Advice Note BA 16/84, Chapter 7.

The substructures are assessed, for overall stability and

structural strength, based on the use of BA 55/94 as described

in Section 2. For any retaining walls or abutments that fail

the assessment, defined by an inadequate factor of safety, the

cause of failure is identified in the context of the current

structural codes and loadings recommended in Department

Standards and Advice Notes used for the purposes of the

assessment. If the substructure is shown to have a high

factor of safety for any limit state condition this will

suggest that the original design was over-conservative with

respect to current assessment standards. In contrast, if the

substructure has a low factor of safety, i.e. is shown to be

inadequate, this would imply that the current assessment

standards are over-conservative with respect to the original

design. The detailed methodology of the appraisal is

described below.

I3.2 DATA COLLECTION AND PROCESSING

Enquiries were made to the Department of Transport Regional

Office Network Management and Construction Divisions and/or

their Agents seeking information on existing retaining walls

and bridge abutments that met the following criteria:

I + substructures more than 10 years old

I+original design data and construction records readily

available

I+selection of substructures to illustrate a range of

structural types and backfill materials

I + retained height of backfill in excess of 5m.

Responses were received from 10 organisations which were then

visited by T~ staff who undertook a preliminary examination

and review of data on potential substructures for the

appraisal. All information was recorded on proforma sheets as

shown in Appendix A. A total of 38 substructures were

initially selected comprising 11 retaining walls and 27 bridge

abutments.

6

After a detailed review of the acquired data a number of

substructures were rejected from the appraisal because of:

+ incomplete or inadequate data available

+ structural form not easily analysed e.g. counterfort

abutments, anchored structures.

This review process reduced the number of suitable

substructures to

arbitrary number

substructure for

25 grouped as shown in Table 3.1. An

(between 1 and 25) was assigned to each

reference purposes.

Table 3.1 Summary of substructure groups

substructure group Substructure Total number

reference number in group

Cantilever abutment, 1, 4, 5, 7, 8, 9

vertical stem,spread 11, 12, 16 and

footing 19

Cantilever abutment, 14, 15, 17 and 4+

vertical stem, piled 20

footing

Cantilever abutment, 21, 22, 23, 24 5

inclined stem, and 25

spread footing

Retaining wall, 2, 3, 6, 9, 10, 7

vertical stem, 13 and 18

spread footing

3.3 ASSESSMENT CALCULATIONS

For each substructure two sets of assessment calculations are

performed using the nominal assessment loads defined in

Departmental Standard BD 21/93 and the earlier version BD

21/84. This has been undertaken to enable a comparison to be

made and identify any significant changes in the adequacy of

the substructures due to the differences in the assessment

load criteria.

The data for each substructure is input to a Lotus worksheet

7

so that the assessment calculations can be conveniently

carried out. This approach also allows sensitivity analyses

to be undertaken to determine the effect of change in selected

parameters such as highway live loads or soil parameters on

the overall stability and internal strength of the structural

elements.

There are two sets of worksheets for calculations using

assessment standards BD 21/84 and BD 21/93 respectively. Each

assessment comprises three worksheets as shown in Appendix B.

+ worksheet A: data input

+ worksheet B: ultimate limit state calculations

4’ worksheet C: serviceability limit state calculations

To demonstrate the analyses undertaken, assessment

calculations undertaken ‘by hand’ using loads as defined by

Departmental Standard BD 21/93 are presented in the Appendices

as follows:

+ Appendix C. Example assessment: retaining wall

+ Appendix D. Example assessment: bridge abutment

These example assessments describe the assumptions made and

identify the appropriate reference and usage of British and

Departmental Standards and Advice Notes.

All the substructures are assessed for ultimate (ULS) and

serviceability (SLS) limit states as shown in Table 3.2. For

each assessment condition the adequacy of the substructure is

defined in terms of a factor of safety. The factors of safety

are compared to values stated in appropriate British Standards

and Codes of Practice. Assumptions made in connection with

the limit state conditions are described below:

Ultimate limit state condition (ULS)

For the ULS condition it is assumed’that:

+ no drainage exists behind the wall, i.e. the highest

water ‘level in the backfill is equivalent to the lowest

crest level of the overall substructure

8

8

Table 3.2 Summary of assessment conditions

I rAssessment condition

Element

ULS SLS

sliding allowable bearing

Soil pressure

ultimate bearing settlement

pressure

maximum moment in maximum moment in

wall stem wall stem

Structure shear in stem

shear and punching

shear in base

+ allowance is made for a lm deep excavation below ground

level in front of the wall to take account of subsequent

installation of buried services, i.e. ground level in

front of the substructure was reduced by lm

+ the worst credible combination of dead and live loads is

applied to the substructure

For the ULS of the soil, active earth pressures (K,) are used

in conjunction with the design methods given in BS 8002: 1994

and BS 8004: 1986.

For resistance to sliding the horizontal earth pressure of any

ground in front of the wall is taken into account in the

calculations with an allowance of lm for unplanned excavation.

The substructures are not assessed for overturning and slip

failure of the surrounding soil. This decision is taken in

order to rationalise the scope of calculations for the

appraisal.

For the ULS condition of the structural elements the analysesare carried out using both active, K., and at rest, K? earth

pressures for the backfill material. The partial load factor

9

Tm for earth pressure generated by the backfill is taken as

1.5 in accordance with BD 30/87. The same factor is also

applied to the highway surcharge acting on the backfill, see

Section 4.1.3. It is assumed that there is no contribution of

earth pressure from any soil in front of the wall. This is

because excavation of ground directly in front of the wall

might occur for maintenance/repair work to the substructure or

foundation. The conse~ence of this is to increase the

calculated maximum bending moment and shear force in the wall

stem. It is also assumed that, at ULS, movement of the

substructure would be such that wall adhesion and wall

friction should be ignored for the backfill. An additional

moment, due to vertical eccentricity of the substructure, is

also applied.

Serviceability limit state condition (SLS)

For the SLS condition it is assumed that:

+ the water level in the backfill corresponds to the design

drainage conditions behind the substructure

+ the worst credible combination of dead and live loads in

service is applied to the substructure.

As for the ULS of the soil, active earth pressures (K,) are

used in conjunction with the design methods given in BS 8002:

1994 and BS 8004: 1986.

The allowable bearing capacity of the soil is also calculated

in order to check the anticipated total and differential

settlement and hence tilt of the substructure under working

loads. For the purposes of the appraisal a tilt of 1 in 500

is assumed as the maximum tolerable movement to satisfy the

SLS condition (Burland and Wroth, 1975).

For structural elements ‘at rest’ earth pressures, &, are used

in the assessment. The partial load factor Tm for earth

pressure generated by the backfill itself is taken as 1.0.

Earth pressure from any ground in front of the wall is taken

into account, although a lm reduction in height was made for

unplanned excavation. Adhesion and friction at the

backfill/wall interface are taken into account on the basis

that this is a reasonable assumption for the in-service

performance of the substructure.

10

4 FINDINGS FROM ASSESSMENT APP~ISAL

The calculated factors of safety representing the assessed ULS

and SLS conditions for each substructure have been compared

for both sets of assessment calculations based on the usage of

BD 21/93 and BD 21/84, see Appendix B. The resulting factors

of safety indicate that there is little or no difference due

to the changes in loading criteria between BD 21/84 and BD

21/93 for all limit state conditions investigated. In view of

this only the findings of the appraisal using BD 21/93 are

discussed in detail below.

There are no substructures which are identified as having

consistently low or inadequate factors of safety. The

majority of the investigated substructures are more than

adequate under the assessment loads with high factors of

safety for the limit state conditions. Some substructures are

inadequate with respect to specific assessment conditions.

The detailed findings are set out below.

4.1 ULTIMATE LIMIT STATE

4.1.1 Resistance to sliding (ULS)

The derived factors of safety based on BD 21/93 are shown in

Fig 2 for resistance against sliding. In general load

combination (a) gives higher factors of safety than load

combination (b) which includes the highway loading (refer to

Appendices C and D for definition of loadings). The exception

to this are all piled abutments and abutments on spread

footings, substructures 8,11,12 and 16 where load combination

(a) gives the lower factor of safety than load combination

(b), see Fig 2.

The majority of substructures have adequate factors of safety

ranging typically between 2 and 4. However a number of

abutments and retaining walls on spread footings

(substructures 1, 2, 4, 8, 9, 10, n(a), 13 and 18(b)) have

factors of safety of less than 2 and are considered inadequatewith respect to sliding in accordance with CP 2 (1951). Sub-

structure 17 also has an inadequate factor of safety for load

combination (a) but as it is a piled abutment it can be

discounted as the effect of piled foundations has been ignored

in the assessment calculations. Although these substructures

have factors of safety of less than 2 only substructure 2

(retaining wall on spread footings) has a factor of safety

11

less than unity indicating apparent instability and failure

for this ULS condition.

4.1.2 Bearing pressure (ULS)

The calculated factors of safety based on BD 21/93 for maximum

localised bearing pressures are shown on Fig 3. In general

the majority of substructures have an adequate factor of

safety (greater than 2) against exceeding the ultimate bearing

capacity of the foundation. Substructure 1, is an abutment on

spread footings founded on dense cemented sand, whilst

substructures 6 and 7 are a retaining wall and abutment

respectively on spread footings founded on strong rock. As

would be expected these substructures are calculated to have

high factors of safety ranging between 9 and 17. In addition

the abutments with sloping stems (substructures 21 to 25) were

also found to have high factors of safety, typically between 3

and 7.

Seven substructures have inadequate factors of safety

(substructures 3, 13, 14, 17, 18, 19 and 20) and of these

substructures 14, 17 and 20 can be discounted as they are

piled abutments. Substructures 3 and 18 are retaining walls

on spread footings and substructure 19 is an abutment on

spread footings are deemed to be inadequate with respect to

ultimate bearing resistance. Substructures 3 and 19, however,

appear to be adequate in terms of allowable bearing capacity

and settlement of the foundations as shown in Section 4.2.1.

4.1.3 Wall moments (ULS)

The derived factors of safety for the maximum bending moment

generated in the wall stem with respect to the ultimate moment

of the reinforced concrete section are shown in Fig 4. Two

cases representing the earth pressures generated by the

backfill have been analysed:

+ Case 1: 1.5 times the earth pressure coefficient ‘at

rest’, KO

+ Case 2: 1.5 times the active earth pressure coefficient,

K,

The partial load factor Tm for earth pressure generated by the

backfill has been taken as 1.5 in accordance with BD 30/87.

It is unclear in the D~B whether this partial factor should

also be applied to live loads. In the case of design BD 37/88

12

cl. 5.8 indicates that partial load factor of 1.5 applies to

live loads with respect to earth pressure calculations. As no

definitive guidance is given in the D- for assessment the

same partial load factor has been applied to the highway

surcharge acting on the backfill. This will affect the moment

and shear resistance calculations for the stem.

‘FromFig 4 it can be seen that all but one substructure

(substructure 2) have an adequate factor of safety greater

than 1 for this assessment condition. With this exception,

the factors of safety range between:

+ for case 1: 1.04 to 10.10

+ for case 2: 1.53 to 13.44

The sloping wall abutments have the highest range in factors

of safety of all four groups and appear to have been over

designed with respect to this limit state condition.

As can be expected the assessment calculations based on ‘at

rest’ earth pressures (case 1) generate higher moments in the

wall stem of the substructures and thus lower factors of

safety than those based on using active earth pressures. The

effect of using 1.5 KO instead of 1.5 K, is an average decrease

in the factor of safety of some 36% for vertical stem

retaining walls and abutments and of 25% for sloping stem

abutments. Even so all the substructures, except substructure

2, indicate a more than adequate factor of safety for this

condition using the more onerous requirement of ‘at rest’

earth pressures in the backfill.

Only substructure 2 (vertical retaining wall on spread

footings) has an inadequate factor of safety of less than

unity (0.52) under ‘at rest’ earth pressures and (0.76) under

active earth pressures. Nevertheless there appears to be no

visual evidence of distress or cracking to this structure

based on the assessment inspection reports by the relevant

Agency/Authority.

In order to evaluate the influence of using a factored highway

live load the calculations were re-run using unfactored values

i.e adopting a partial load factor of 1 on the highway

surcharge. The result was to increase the factors of safetY,

for both case 1 and case 2 by between 5% and 25%. Thus the

13

use of a partial load factor on live loads is potentially

significant in assessment for moment and thus also shear

resistance in the stem.

4.1.4 Wall shear (ULS)

The derived factors of safety for the maximum shear stress

generated in the wall stem with respect to the ultimate shear

stress of the reinforced concrete section are shown in Fig 5.

As with the moment calculations, two cases representing ‘at

rest’ and active earth pressures generated by the’backfill

were analysed in conjunction with a partial load factor Tm of

1.5 in accordance with BD 30/87: i.e. case 1 and case 2

respectively. As can be expected the assessment calculations

based on ‘at rest? earth pressures (case 1) generate higher

shear stresses in the wall stem of the substructures and thus

lower factors of safety than those based on using active earth

pressures. The effect of using 1.5 KO instead of 1.5 K, is an

average decrease in the factor of safety for this assessment

condition of some 36% for all substructures irrespective of

whether the wall is vertical or sloping.

For case 1 nearly all the abutments are inadequate with

factors of safety against shear less than 1. Only

substructures 4, 15, 16 17 and 19 have factors of safety above

unity. As would be expected higher factors of safety, between

1 and 3, occur for case 2 for the majority of abutments, see

Fig 5.

All the retaining walls have factors of safety less than unity

for both cases 1 and 2, except substructure 13 for case 2, and

are apparently inadequate for this assessment condition.

Despite the low factors of safety for many of the

substructures there appears to be no visual evidence of

distress or cracking based on the assessment inspection

reports by the relevant Agency/Authority.

As discussed in Section 4.1.3 the use of a partial load factor

on live loads can be significant. The shear resistance in the

stem was increased for both case 1 and case 2 by between 1%

and 34%.

4.1.5 Base’and punching shear (ULS)

The factors of safety derived for both base shear (at worst

critical vertical section beneath the stem wall extending the

14

full width of the base) and punching shear (taken at a

critical section on a perimeter 1.5 times the effective depth

of the base from the wall stem boundary) with respect to the

ultimate shear stress of the reinforced concrete section are

shown in Fig 6. Only substructure 12, an abutment on spread

footings, is inadequate for case

exception, all the substructures

safety against base and punching

follows:

+ base shear: 1.17 to 3204.0

1 conditions. With this

have an adequate factor of

shear greater than unity, as

.+ punching shear: 2.09 to 19.06.

A number of substructures in all four groups do however appear

to have been originally over designed with respect to this

assessment condition with significantly high factors of safety

for either shear or punching shear, see Fig 6. It is of

interest to note that for abutments a high factor of safety

for base shear does not necessarily imply a high factor of

safety for punching shear. For the retaining walls in Fig 6,

the factors of safety for punching shear are always higher

than for base shear.

4.2 SERVICEABILITY LIMIT STATE

4.2.1 Allowable bearing pressure (SLS)

In order to check the likely settlement and differential

settlement of each substructure under serviceability limit

state conditions the allowable bearing capacity of the

foundation was evaluated. This was taken as approximately a

third of the ultimate bearing capacity calculated in Section

4.1.2 as a reasonable value to limit settlements to normal

acceptable structural design tolerances (CP 2, 1951). Factors

of safety were then calculated for the bearing pressure of the

substructure with respect to the allowable bearing capacity of

the foundation. The substructure is deemed to be adequate if

the factor of safety is greater than 1.

The derived factors of safety are plotted in Fig 7. The

majority of the substructures have factors of safety in the

range 1 to 3 and are, therefore, adequate with respect to

tolerable movement. Substructures 6 and 7 are founded on

strong rock and have factors of safety of 9.67 and 16.12

15

respectively.

Three substructures (17, 18 and 20) have factors of safety

less than 1. Of these, however, substructures 17 and 20 are

founded on piles which are not taken into account in the

assessment calculations. Substructure 18 is a retaining wall

on spread footings and total settlements are estimated to be

some 80mm. In this case differential settlements are likely

to lead to visual cracking in the substructure although none

are reported in the inspection reports.

4.2.2 Wall moments (SLS)

.The maximum bending moment in the wall stem under

serviceability limit state conditions (i.e. full drainage in

the backfill, earth pressures generated by the backfill

derived using KO, and a partial load factor Tm = 1) was

compared to the ultimate moment of resistance. A factor of

safety greater than 1 indicated that the substructure is

adequate. The derived factors of safety are plotted in Fig 8

and indicate that all substructures are adequate for this

assessment condition except substructure 2 with a factor of

safety of 0.76. Lack of detail of reinforcement has made it

impractical to check the acceptable limits of cracking in

accordance with Departmental Standard BD 30/87.

Not surprisingly, the results are similar to those derived

under ULS conditions (i.e. no drainage in the backfill, earth

pressures derived using KO, and a partial load factor Tm = 1.5)

but with a general increase in the factor of safety. There

is, however, a large variation in the increase in the factor

of

5

IN

To

safety ranging from 11% to 108% with a mean of 36%.

APPRAISAL TO DESIGN STANDARDS TO ASSESS OVER-CONSERVATISM

DESIGN

investigate the effect of changes in design standards on

the adequacy of substructures an appraisal to current design

standards has been undertaken on the substructures. Current

Departmental Design Standards and Codes of Practice, as

invoked by Departmental Standard BD 24/92 have been used for

the design appraisal.

The design appraisal is undertaken in a similar manner to the

appraisal to assessment standards outlined in Section 3.3.

The principal differences used in the design appraisal are

16

outlined below:

1. The design loads are based on those set out in

Departmental Standard BD 37/88, Chapter 6. Specifically

the highway loading incorporates Type HB live loading on

the substructure from the superstructure/bridge deck

where appropriate.

2. For appraisal of the structural elements vertical and

horizontal earth pressures due to retained fill are

factored, Tm, in accordance with Departmental Standard BD

37/88, c1.5.8.1.2 as summarised below in Table 5.1. The

highway surcharge on the retained fill is factored

similarly.

Table 5.1 Factored earth pressures for design

Ultimate limit Serviceability

state limit state

Vertical 1.2 1.0

loads

Non- vertical 1.5 1.0

loads

In accordance with cl. 5.8.1.3, however, where the

application of Tm as given in Table 5.1 causes a less

severe total effect, than if ~m is taken as 1, then a

value of 1 is adopted. This is the case for the

calculation of sliding resistance where Tm = 1 for

vertical backfill loading produces a more severe effect.

3. The live load surcharge on the retained fill is taken as

45 units of type HB loading, i.e. 20kN/m2

4. The minimum depth of unplanned excavation in front of the

substructure is taken as not less than 10% of the total

height of the retained wall in accordance with cl.

3.2.2.2, BS 8002: 1994.

With regard to item 2 above, for the ULS condition of the soil

the design appraisal is based on the principles set out in BS

8004: 1986 using unfactored nominal loads as invoked by

17

Departmental Standard 30/87 (the same procedure has been used

for the appraisal to assessment standards).

The calculations have again been performed using three

worksheets and these are presented in Appendix E.

Representative peak strength soil parameters have been used

consistently throughout the design appraisal in order to allow

a direct comparison with the assessment findings of the

effects of changes in structural requirements. The

significance of using factored soil strength parameters is

discussed in Section 7.

6 FINDINGS FROM DESIGN APPRAISAL

In general, the results given in Appendix E indicate that the

appraisal to current design standards gives lower factors of

safety for the ULS condition of the soil i.e. sliding and

bearing pressure, than the appraisal to current assessment

standards based on BD 21/93. In contrast for the ULS and SLS

conditions of the structural elements the design appraisal

generally gives higher factors of safety than the appraisal to

assessment standards, although there are a number of

exceptions.

The majority of substructures are more than adequate under the

design loads with generally high factors of safety for the

limit state conditions investigated. Those substructures found

to exhibit partial inadequacy with respect to specific limit

state conditions under assessment standards are also

inadequate under the design standards. The detailed findings

are set out below.

6.1 ULTIMATE LIMIT STATE

6.1.1 Resistance to sliding (ULS)

Fig 9 shows the derived factors of safety. For abutments

under load combination (a) the factors of safety calculated

using design standards are almost identical to those derived

using the assessment standards based on BD 21/93 (compare

Appendix B worksheet B to Appendix E worksheet B). This is to

be expected as earth pressures from the retained backfill are

the same in the two cases. The exceptions to this general

rule are retaining walls 2 and 3 which have marginally lower

factors of safety for the design appraisal.

For load combination (b), however, the calculated factor of

safety is between 5% and 22% lower using design standards than

with assessment standards and reflects the increase in highway

loading due to the introduction of type HB surcharge loading

on the retained backfill as well as the combination of type HA

and HB live loading from the bridge deck where appropriate.

“For all substructures, load combination (a) gives higher

factors of safety than combination (b) which includes the

highway loading (refer to Appendices B and C for definition of

loadings). This is consistent with the assessment study

findings.

In the main, the substructures have adequate factors of safety

ranging typically between 2 and 4. Substructures 1, 2, 4, 8,

9, 10, 11, 13, 17 and 18(a) have, however, factors of safety

of less than 2 and are considered inadequate with respect to

sliding in accordance with CP 2 (1951). Again this finding is

generally consistent with the assessment study. As explained

in Section 4.1.1, substructure 2 (retaining wall on spread

footings) is of concern having an apparent factor of safety

less than unity indicating instability. This substructure is,

however, marginally stable under the design appraisal for

load combination (a) and (b) with factors of safety.of 1.07

and 1.02 respectively.

6.1.2 Bearing pressure (ULS)

The calculated factors of safety are shown in Fig 10. In

general the results are consistent with the appraisal study.

The majority of substructures have an adequate factor of

safety (greater than 2) against exceeding the ultimate bearing

capacity of the foundation. Generally however factors of

safety for abutment substructures calculated using design

standards are marginally lower by up to 2% than those from

assessment standards. The exception to this are substructures

1 and 5 which have increased factors of safety of 14% and 2%

respectively. For retaining walls the converse is true with

the factors of safety increasing by between 5% and 14% when

using design standards.

Those substructures that are inadequate to assessment

standards are also identified as inadequate in the

calculations to design standards. Substructures 1, 6 and 7are calculated to have high factors of safety ranging between

9.26 and 19.09 reflecting the competency of the foundation

19

soils. The majority of abutments and retaining walls on

spread footings were adequate with high factors of safety

ranging between 2 and 4. In particular the abutments with

sloping stems (substructures 21 to 25 inclusive) were also

found to have high factors of safety, ranging between 3.33 and

6.0 suggesting that they have been over-conservatively

designed.

Eight substructures (3, 14, 15, 16, 17, 18, 19 and 20) have

inadequate factors of safety (less than 2). As explained in

Section 4.2.1 substructures 14, 17 and 20 are piled abutments

where the benefits of piling have not been taken into account.

Substructure 18 is a retaining wall on spread footings and has

a factor of safety less than unity and is considered to be

inadequate with respect to ultimate bearing resistance and

unacceptable settlement of the foundation.

6.1.3 Wall moments (ULS)

Two load cases representing the earth pressures generated by

the backfill itself were analysed. For each case the partial

load factor Tm for earth pressure generated by the backfill

has been taken as 1.5 in accordance with BD 37/88 (which is

also consistent with BD 30/87). As explained in Section 5 the

highway surcharge on the retained fill is also factored.

+ case 1: 1.5 times the earth pressure coefficient ‘at

rest’, KO

+ case 2: 1.5 times the active earth pressure coefficient,

K,.

The derived factors of safety for the maximum moments

generated in the wall stem with respect to the ultimate moment

of the reinforced concrete section are shown in Fig 11. With

the exception of substructures 2 and 11, the factors of safety

are in the ranges:

+ for case 1: 1.13 to 22.74

+ for case 2: 1.3 to 28.37.

The results confirm that the majority of the substructures

were over-c’onservatively designed with respect to this limit

state condition (Fig 11). The highest factors of safety

(greater than 20) were found for two of the sloping abutment

20

walls (substructures 22 and 23). only substructures 2 and 11

(vertical retaining wall and abutment on spread footings) have

inadequate factors of safety of less than unity (calculated

factors of 0.52 and 0.95 respectively) under ‘at rest’ earth

pressures. The factors of safety calculated using active

earth pressures are 0.66 and 1.3. As stated in Section 4.1.3

there appears to be no visual evidence of distress or cracking

to this structure based on the assessment inspection reports

by the relevant Agency/Authority.

As can be expected the design calculations based on ‘at rest’

earth pressures (case 1) generate higher moments in the wall

stem of the substructures and thus lower factors of safety

than those based on using active earth pressures. Even so all

the substructures, except substructure 2 and 11 (for case 1

loading only), indicate a more than adequate factor of safety

for this limit state using the more onerous case based on ‘at

rest’ earth pressures in the backfill.

For both cases 1 and 2 the factors of safety derived using

current design standards are generally higher than the factors

of safety calculated using assessment standards for abutments

and retaining walls founded on spread footings (including the

sloping abutments) . The maximum increase is 125% for

substructure 23 (sloping abutment). For the abutments on

piled foundations there is a reduction in the factors of

safety, except substructure 20 for which the converse is true.

Substructure 14 shows the maximum reduction from assessment to

design calculated factor of safety of 25%. Even so the

reduction results in a factor of safety of 1.13 which is still

adequate for structural stability under ultimate limit state

conditions.

6.1.4 Wall shear (ULS)

Fig 12 shows the calculated factors of safety for the maximum

shear stress generated in the wall stem with respect to the

ultimate shear stress of the reinforced concrete section. A

similar trend is identified from the results when compared to

the results obtained for the assessment appraisal described in

Section 4.1.4.

As expected the calculations based on ‘at rest’ earth

pressures (case 1) generate higher shear stresses in the wallstem of the substructures and thus lower factors of safety

than those based on using active earth pressures. The factors

21

of safety are summarised below:

+ case 1: 0.31 to 1.60

4 case 2: 0.39 to 2.17.

The piled abutments (substructures 15 and 17) have higher

factors of safety than the other three types of substructure

(Fig 12).

The effect of using 1.5 KO instead of 1.5 K, is an average

decrease in the factor of safety of some 30% for all

substructures, although there is a larger variation for the

retaining walls. This is a similar reduction to that found

for the assessment study. Relatively few substructures have

an adequate factor of safety against shear for both cases 1

and 2. These are abutments 4, 15, 16, 17 and 19 and retaining

wall 13.

The majority of substructures have an inadequate factor of

safety for case 1 but are adequate with respect to case 2

Retaining walls (substructures 2 and 3) have an inadequate

factor of safety for both case 1 and case 2 conditions.

Despite the fact that a large number of substructures are

inadequate with respect to case 1 and, to a lesser extent with

case 2, there appears to be no visual evidence of cracking

based on the assessment inspection reports by the relevant

Agency/Authority. These substructures are therefore

apparently over-conservatively designed with respect to

current design standards for this limit state condition.

6.1.5 Base and punching shear (ULS)

The factors of safety derived for both base shear and punching

shear with respect to the ultimate shear stress of the

reinforced concrete section are indicated in Fig 13.

All the substructures have an adequate factor of safety

(greater than 1) against base and punching shear, as follows:

+

+

Most

base shear: 1.06 to 253.57

punching shear: 2.02 to 21.44.

substructures do appear, however, to have been originally

22

over-conservatively designed with respect to these conditions

with factors of safety for either shear or punching shear

greatly in excess of 1. It is worth noting that in nearly all

cases a significantly high factor of safety for base shear

(e.g. greater than 5) does not necessarily imply a high factor

of safety for punching shear and vice versa, see Fig 13. All

retaining walls on spread footings have very high factors of

safety against punching shear ranging between 7.57 and 21.44.

Compared to the results of the assessment study, generally

there is an increase in the factor of safety for this ultimate

limit state condition for most substructures as follows:

4 base shear; all substructures: 9% to some 1900% increase

+ punching shear; abutments: 0.29% to 8% decrease

retaining walls: 12% increase.

There appears to be no specific reason for these large

variations other than the use of the design loading and

partial factors as described in Section 5. Substructure 23

(sloping abutment) has the largest increase of 1886%. This isbecause the net shear force in the base beneath the stem is

very small (some 17kN) when using factored loads for design as

described in Section 5. It is therefore concluded that the

factors of safety for this ultimate limit state condition are

very sensitive to the loading criteria used.

6.2 SERVICEABILITY LIMIT STATE

6.2.1 Allowable bearing pressure (SLS)

The factors of safety, for the bearing pressure of the base of

the substructure with respect to the allowable bearing

capacity of the foundation, are plotted in Fig 14. Generally

the substructures have factors of safety in the range 1 to 3

and are, therefore, adequate with respect to tolerable

movement (a factor of safety greater than 1 has been taken to

be acceptable in accordance with BD 30/87). Substructures 6

and 7 are founded on strong rock and have factors of safety of

17.20 and 9.28 respectively.

As for the assessment appraisal, three substructures (17, 18

and 20) have factors of safety less than 1. Of these,

however, substructures 17 and 20 are founded on piles which

23

have been ignored in the design calculations. Tots 1

settlement of substructure 18 (a retaining wall on a spread

footing) is estimated to be 74mm. Differential settlement is

likely to lead to visible cracking in the substructures,

although none has apparently been detected.

Compared to the assessment appraisal results, there is an

overall reduction in the factor of safety for abutments of

between O% and 4%. For retaining walls, however, the factor

of safety increases between 5% and 13.3%.

6.2.2 Wall moments (SLS)

.The derived factors of safety are plotted in Fig 15 and

indicate that all substructures are adequate for this

assessment condition (factor of safety greater than 1) except

substructure 2 which has a factor of safety of 0.92.

The results are similar to those determined using ULS design

conditions, but with a general increase in the factor of

safety as a result of the reduction in applied moment using

SLS conditions. The increase in the factor of safety ranges

from 26.4% to 119% with a mean increase of 36%.

Compared to the assessment results, there is generally an

increase in the factor of safety using current design

standards for the majority of substructures irrespective of

type. This increase ranges between 1.1% to 127.1% and

indicates that the maximum moment in the wall stem has

decreased using design loading standards. For substructures

4, 5, 7, 11, 14, 15 and 17 (comprising some vertical wall

abutments on spread and piled footings) there is, however, a

reduction in the factors of safety. This implies that the

moment in the wall has increased for these substructures due

to the design standard loadings.

7 SOIL STRENGTH P~ETRIC STUDY

All soil data used in the calculations have been based on

representative peak strength soil data in order to allow a

direct comparison of the effects of load changes in structural

requirements. A factor of safety of 1 has been applied to the

soil strength data both for assessment and design

calculations. BS 8002: 1994 cl. 3.2.5 recommends, however,

that soil strength parameters for the design of retaining

structures are based on factored representative peak strengths

24

in conjunction with a factor of safety (M) of 1.2, or the

representative critical state strength with a factor of safety

of 1.

There is no advice given on the definition of representative

soil parameters and whether they should be based on worst

credible or moderately conservative data. For this reason

there is potential ambiguity in the selection of soil strength

parameters and the use of various factors of safety for the

limit state conditions of the substructure.

The significance of any effect of changes in soil parameters

has been investigated by re-analysing the two example

assessments presented in Appendices B and C (substructures 1

and 3). The representative peak soil strength

and @’) used throughout the analyses have beenvalue, F, ranging between 0.8 and 2 such that:

C’F = c~/F and o’~ = @’/F.

parameters (c’

factored by a

A factor of 0.8 can be considered as representing an upper

bound limit to soil strength whilst a factor of 2 is

significantly over-conservative. The following limit state

conditions have been investigated:

+ sliding at ultimate limit state

+ wall moments at ultimate limit state

+ wall moments at serviceability limit state.

The results of this parametric study are summarised in Table

7.1 and are also shown in Fig 16. As expected the general

trend is that there is a reduction in the factors of safety

for the various limit state conditions with the increase in

the factor on soil strength. The reductions approximate to a

set of exponential curves. The greatest reduction occurs over

the region, between 0.8 and 1.2 factored soil strength i.e.

typically t 20% of the representative peak soil strength

parameters which have an equivalent factor of safety of 1 and

have been used in this appraisal.

For sliding the reduction in the factor of safety for this

condition is significant as shown in Table 7.1. An increase.

in the factor of safety on soil strength from 1 to 1.2 results

25

in a reduction of some 30% in the factor of safety under

current design standards if BS 8002: 1994 cl. 3.2.5 is

invoked. Both substructures 1 and 2 are rendered inadequate

if the soil strength is factored by 1.5 or greater.

Table 7.1 Variation in factors of safety on limit state

condition

Factor on soil strength

Condition

0.8 1 1.2 1.5 2

Sliding 2.77 1.67 1.17 0.79 0.50

3.10 1.63 1.12 0.78 0.51

ULS Wall 4.47 3.32 2.79 2.39 2.08

moment, 1.35 1.01 0.85 0.73 0.64 -

1.5 KO

ULS Wall 7.09 5.02 4.04 3.27 2.67

moment, 2.24 1.53 1.22 0.98 0.80

1.5 K,

SLS Wall 6.26 4.54 3.78 3.21 2.77

moment, 1.80 1.33 1.12 0.95 0.83

K

Legend 2.77 = substructure1: abutmenton spreadfootings3.10 = substructure3: retainingwall on spreadfootings

In terms of the effect on the adequacy of the structural

elements there is a similar reduction, in relative magnitude,

over the region between 0.8 and 1.2 factored soil strength.

Substructure 3 is inadequate for ULS moment condition using

1.5 KO (FOS = 0.85). Substructure 1 is adequate for all moment

limit state conditions even if the factor on soil strength is

increased to 2.

In general, therefore it appears that the adequacy of the

substructure is sensitive to the choice of soil strength

26

parameters. This has a significant influence on the use and

relevance of partial load and material factors currently

adopted in assessment and design standards.

8 CONCLUSIONS

The conclusions of this work are set out below:

1. The results of the assessment appraisal indicate that the

majority of the existing substructures are more than

adequate under the current assessment standards. There

is an insignificant effect due to the difference in

loading criteria between BD 21/93 and the now superseded

BD 21/84 for all limit state conditions investigated.

2. From the assessment and design appraisal a number of

abutments and retaining walls are identified as having

consistently low or inadequate factors of safety with

respect to the ULS conditions for the soil: sliding and

bearing pressure, see Figs 2 and 3. None of these

substructures are reported as showing signs of distress.

This implies that the appraisal of these substructures

has been over-conservative using current design and

assessment standards.

3. The choice of soil strength parameters has a significant

influence on the adequacy of the substructures,

particularly the ULS and SLS conditions for the soil, see

paragraph 7 below. It is thought that the choice of soil

strength parameters used

foundation are lower and

adopted for the original

in the assessment for the

thus more conservative than

design.

4. The majority of abutments and retaining walls, have high

factors of safety for the structural element limit state

conditions. This would suggest that the original design

of these substructures was more onerous than current

assessment and design standards. The magnitude of loads

and earth pressures acting on the substructures, used in

the assessment and design calculations, would appear to

be significantly lower than that adopted in the original

design. This is because, for many of the substructures,

it appears that the original design loads are derived

using partial and material factors and load combinations

appropriate for the design of the equivalent

27

5.

6.

7.

9

superstructure. This has led to an over-estimate of the

loads and pressures on the substructures analysed

resulting in the design and construction of over-sized

reinforced concrete structural elements. This appears to

be the case for wall moments and base and punching shear

at ULS conditions for which very high factors of safety

have been derived using current assessment and design

standards.

The exception to this is shear resistance of the stem at

ULS where many substructures are inadequate. This is

believed to be due to over-conservatism in the current

assessment and design standards because of the use offactored highway surcharge on the retained fill using Tm,

in accordance with Departmental Standard BD 37/88,

c1.5.8.1.2, see Section 5.1. The use of a partial load

factor on live loads is shown to be potentially

significant in assessment for moment and thus also shear

resistance in the stem, see Sections 4.1.3 and 4.1.4.

In addition to the above, adopting earth pressures for

the backfill (i.e. K, or &) based on realistic soil

strength parameters and nominal dead and live loads for

design or assessment, results in lower moments and shear

forces and, hence, the need for smaller structural

sections.

The current Departmental Standards and Advice Notes for

design and assessment are inconsistent in their guidance

on the choice of soil strength parameters and advocate

either representative peak or worst credible values. The

findings of the appraisal highlight the sensitivity of

the assessment and design calculations to the choice of

soil strength parameters used. This has a significant

effect on the interpretation of the adequacy of the

substructure.

The work described in this report forms part of the research

programme of the Civil Engineering Resource Centre of the TRL.The advice of Dr J Temporal and Dr D R Carder of TRL in

preparing this report is gratefully acknowledged.

Thanks are due to the DOT Regional Office Network Management

28

and Construction Divisions and their Agents for supplying data

on the substructures.

10 REFERENCES

BRITISH STANDARDS INSTIT~ION

BS 8004:1986, Code of practice for foundations.

BS 8002: 1994, Code of practice for earth retaining

structures.

B~D, J.B., BROMS, B.B. and DEMELLO, V. (1977). The

behaviour of foundations and structures: state of the art

report, session 2. Proc. of the 9th. Int. Conf. on Soil Mech.

and Fdn. Engng. Tokyo, 1977, 2, 495-546

B~D, J.B. and nOTH, C.P. (1975) . Settlement of

buildings and associated damage. Building Research

Establishment Current Paper CP 33/75.

Station, Department of the Environment

DEPARTMENT OF TRANSPORT (1993). Design

Bridges

Volume 1: Highway structures: Approval

design

Section 3: General design.

Building Research

Manual for Roads and

procedures and general

Part 1 Departmental Standard BD 24/92: The design of

concrete highway bridges and structures.

Part 2 Departmental Standard BD 37/88: Loads for highway

bridges.

Volume 2: Highway structures: Design (Substructures and

spcial structures), materials.

Section 1: Substructures.

Departmental Standard BD 30/87: Backfilled retaining

walls and bridge abutments.

29

Departmental Standard

Section 2: Special structures.

Departmental Standard

type structures

BD 32/88: Piled foundations.

BD 31/87: Buried concrete box

Volume 3: Highway structures: Inspection and maintenance.

Section 4: *sessment

Part 3

Part 4

Part 9

WE; T.

Wiley and

Departmental Standard BD 21/93: The assessment of

highway bridges and structures. (supersedes BD 21/84)

Departmental Advice Note BA 16/93: The assessment of

highway bridges and structures

Departmental Standard BD 34/90: Technical

retirements for the assessment and strengthening

for highway structures: Stage 1 - Older short span

bridges and retaining structures.

Departmental Standard BD 44/90: The assessment of

concrete highway bridges and structures.

Departmental Advice Note BA 34/90: Technical

re~irements for the assessment and strengthening

for highway structures: Stage 1 - Older short span

bridges and retaining structures.

Departmental Advice Note BA 44/90: The use of BD

44/90 - The assessment of concrete bridges and

structures.

Departmental Advice Note BA 55/94: The assessment of

bridge substructures and foundations, retaining

walls and buried structures.

w. and wHIm, R. V. (1969). Soil mechanics. John

Sons, New York.

PECK, R.B., HANSON, W.E. and THORNB~, T.H. (1953).

Foundation engineering. John Wiley and Sons, New York.

30

THE INSTIT~ION OF STRUCT- ENGINEERS (1951). Earth

retaining structures, Civil Engineering Code of Practice No.2,

London.

TOMLINSON, M. J. (1975). Foundation design and constmction.

Pitman and Sons Ltd., London.

31

BA55/94 I

BD21/93 BAI 6/93I I

/’\/1-\ I

/ Is \

Comments

D;c;rn;n~~ gi~e-‘:procedures for ,visualassessment’quantitativeassessmentandloadingcriteria

---- ---- ---

<

substructuadequate based

on visual * ASSESSMENTinspectio COMPLETE

Calculate adequacyfor soil conditions

!

---- --

~Do;u-mentsgive~Iguidanceon :

BD34/90 BA34/90 -::;:;C:r III 1assessmentand

‘relaxationof~factorsofsafety---- ---- ---

===

I ‘‘N&6d-t;;efer--I

Calculate adequacy ofconcrete structural elements

toBS8004,BS8002 andBS6031 foracceptableIfactorsofsafety

BD44/90 BD44/90---- ---- ---

: Need toreferto‘ BS8002 & BS5400

‘I Part 2 and Part 4~ forpartial---- ---

I

factors---- -

ASSESSMENT COMPLETE

Fig 1 Assessment procedure for substructures

~’:::::; Load combination a~~~~~~~~~~~~~Load combination b

Abutments(spreadfootings) Abutmenk@iled)

1 4 5 7 8 11 12 16 19StructureNumber

Abutments(slopingwall/spreadfooting)10

o21 22 23 24 25

StructureNumber

r

● Contribution from piles not included

14 15 17 20StructureNumber

RetainingWalls

2 3 6 9 10 13 18StructureNumber

Fig 2 Resistance to sliding ULS (BD21 /93)

olenbapv - *lenb8peul

0

elenbepv ~lenbepeul

elenbapv lenbapeul

I 1

e>enbepv y eaenbepeul,I I

elenbepv ~ elenbepeul

elenbepv ~ elenbepeulelenbepv y elenbepe”l

elenbapv - -elenbapeui ---. .--r .

0 . 0

elenbepv ~elenbepeul

1

0 m 0

m

eaenbepv~elenbePeul elenbepv ~eaenbepeul

c.-

0 m 0

elenbepv ~elenbepeul elenbapv ~elenbepeul

eaenbepv ~ elenbapeul oaenbopv +

1 I 1

elenbepv ~ elenbepeul

I 10 m

~ elenbepeul

o

e%enbepv elenbepeul

I

elenbepvy elenbepeul

0 m .

—

elenbepvT

elenbepeul

e$enbepv eaenbepeul

I 1

mm

elenbepv elenbepeul

I I

elenbepv elenbepeul

I I

0

* elenbepeul

elenbepv +

0

I I I I0 m o

elenbepv + c elenbepeul

elenbepv ~ elenbepeu!

elenbepv eaenbepeul

i 1

elenbepv elenbepeul

I 1

elenbepv+ elenbepeul

22mm. .-v

Fw

%%

ZZ~,::~!:[;,,;:::::,:,:,::,;.;,;..,..:.:..:.l,:,:,:,:,:,:,

G

#.-$:gn

=

~

g

2

e>enbepv ~ elenbepeul

elenbepv elenbepeul

i I

elenbepv eaenbepeul

r f

:

.

“.-. .--r “

<

elenbepv y elenbepeul

t

---- ---r- -,

olenbep~ e~enbepeul

eaenbapv ~ eaenbepeul

1 I I I0 m 0

elnnbepv eaenbepeul

I I

se>enbepv ~ elenbep~ul ,_

elenbepv~ elenbepeuielenbopv elenbepeul

0 m 0

elenbepvT

elenbep8ul

+Nnm

elenbepv ~ elenbepeul ~

Abutments(spreadfootings) Abutmentsoiled)10

o

10

I 4 5 7 8 11 12 16 19StructureNumber

Abutments(sloping wall/ spread footings)

o21 22 23 24 25

StrucmreNumber

10

nv14 15 17 20

StructureNumber

RetahingWalls

.2 3 6 9 10 13 18

StructureNumber

Fig 15 Bending moment SLS (BD24/92) ,

m

d

1 1 , I I 1 , , t

—oL

o a

m

c.-

,***

0

ASSESSW~ OF S~STRUC-S

.1. INPO-TION SOURCE

1.1 REGION/AGENT/ CONS~TNT*

1.2 NAME

1.3 ADDRESS

1.4 TEL No

1.6 MEETING WITH

2. STRUCTURE DETAILS

2.1 REFERENCE ~

2.2 LOCATION (attach site plan)

2.3 NATIONAL GRID REFERENCE

2.4 STRUCTURE TYPE

2.5 DESIGN INFO-TION AVAI~BLE

1.5 FAX No

1.7 DATE

Y/N

Retaining wall/Abutment”

Drawings/DesignCalculations*

* delete/ mend as appropriate

1

2.6

2.7

3.

3.1

3.2

3.3

3.7

3.8

3.9

DESIGN LOADINGS (describe WT Standards, Codes ofPractice, factors of safety, etc.)

BS 5400: Part 4 Code of practice for design of concretebridgesBS 6031 Code of practice for earthworksBS 8004 Code of practice for foundationsBS 8110 Structural use of concreteBD 37/88 Loads for Highway StructuresCIRIA 104Others?

SURCHARGE LOADING (describe any surcharge loading on backof wall or abutment)

CONSTRUCTION DETAILS

DATE OF CONSTRUCTION

DIMENSIONS (give height, length and thickness)

MATERIALS Reinforced concrete/unreinforced concrete*

TYPE OF CONSTRUCTION Cast-in-situ/precast*

FOUNDATIONS Spread footings/piles/other*(give dimensions, layout, etc.)

NATURE OF BACKFILL (include method of placement andcompaction details)

3.10 NATURE OF RETAINED GROUND Sloping/horizontal”(if sloping, determine angle)

3.11 DRAINAGE MEASURES (drains, weep holes, etc.)

* delete/ send ‘asappropriate

2

4. GEOTEC~ICAL DATA AND SUBSTRUCTURE DESIGN

4.1 SITE INVESTIGATION REPORT AVAILABLE?(if yes attach copy)

Y/N

4.2 GRO~D CONDITIONS (describe)

4.3 GROUNDWATER LEVEL Is it tidal? Y/N

4.4 GEOTECHNICAL PARAMETERS (List parameters used in design andfactors of safety adopted where appropriate for all soils:include backfillj -

PARAMETER

bulk density (Tb)

strength (cu, c’, @’)

stiffness (~, ~)

earth pressure coefficients (K.~~, K.)

wall friction (6)

other parameters?

5. ASSESSMENT OF SUBSTRUCTURES AND FOUNDATIONS

5.1 IS THERE AN EXISTING ASSESSMENT Y/N

(if yes, attach copy)

5.2 HAS STRUCTURE BEEN STRENGTHENED SINCE CONSTRUCTION(if yes, give details and dates)

5.3 DATE OF EXISTING ASSESSMENT

* delete/ mend as appropriate

Y/N

3

5.4 TYPE OF ASSESSMENT visual/analytical/both”

5.5 EXPLORATORY INVESTIGATION UNDERT~EN Y/N(if yes, describe investigation and findings)

5.6 CONDITION SURVEY(if yes, describedistress, movementsoil conditions)

Y/Ncondition findings e.g. degree of

guality of backfill andand cracking,

5.7 REINFORCED CONCRETE DETAILS OF(Design or construction drawingsexample attached)

SUBSTRUCTUREwould show this, see

5.7.1 Concrete strength (quote characteristic cube strength, fCU)

5.7.2 Grade of tensile and compressive steel reinforcement i.e.mild or high strength (250 or 460 N/mm*)

5.7.3 Ascertain reinforcement schedule Give:

bar diameter

bar spacing (centre to centre)

depth of concrete cover (note: this may vary from face t oface across the stem or foundation)

* delete/ mend as appropriate

4

DECK DIMENSIONS WTERWPROPERTIES

,~ ~ ,~

24.0 t90 f90

24.0204 200

24.0 187 !90

296 fee tao

298 176 f90

23e mo 190

240 $7.6 t90

240 f90 100

240 190 f90

LOADING DATA DECK LOADINGON ABUTMENTWD WA c’

60

2M0 126! o

m 12m 6

273 2667 0

446 m o

2610 f249 6

1047 !207 o

97W 2226 0

22% 21?6 o

2W7 !291 o

EARTH PRESSUREMCKFILL

+ Ka KO Kp66

36 027t 0426 3SW

WTERIAL STRENGTH PROPERTIES ‘STRUCTURAL PROPERTIES SOIL PROPERTIES

No Nwlw2tt lttt2hlh2hlh2 ha ZZskmuLssLssLs

620 !7.30 2.m Omow 1.00 4.m Saa 7.3t !.32 a63 o t.mooo

4?T U.Q 2,44 09! 09! 0.78 8@ 062 862 OW 66! O 0?6 04@

626 I!.20 Sa 063063 f.m em 226 7.64 !.W 8M o I.@ !m

Sm f666 f.07 09t Oot 0.61 60 Ow am Om em o 2.a Om

649 !624 1.33 !.62 t.Q i.22 914 O@ 9!4 O@ 914 0 1.22 OW

996 !7.07 t.s3 076 076 09! 701 061 70! 061 7.Q o 091 Om

6~W432.20 IW OW 076 8WOm 8m OW O@ O 076 Om

w Ltdn w LWI-S Imc

16f0 !824 O@ 4 2.76 0.7636

t4aw Qo93 2 $@ l.ml

11.20 4307 047 2 9s4 I.owt

!Sm !044 027 2 366 I.wl

12f9 2366061 2 Sm Oawo

1664 1844 031 3 336 09!79

W6620@t W 6 366 I.ml

34@t4 Mow 8 967 09762

f76f 1633 067 4 $34 097W

fcu Ym

i.w

t.so

t.m

WW wNIVE FY Yms

1.16

1.16

f, t6

t,t6

f fs

FS dNAd AsTLdNA#Asnd*m Uom ti8m bass bssa base

063 006 Oomo Om 006 Oo$m

0s2 Om Ootw 067 Oa Oomo

076 006 00im 092 Om 00!W

,066 003 om4 Oa OM 0W33

‘!49 007 Owfo !,19 007 Omlo

QQ @o +& ah

4Q2 ~ OWW 34

760 4a Ooaw ?8

6902300W34

2~ t~ 00163 46

mwoo!mw

m3wom34

876 3W OWW 36

c“ Ka Kp#d sd

o 0 2s3 3637

6 0 Wf 27m

o 0233 3637

6 0 !72 6626

6 0333 Sm

6 0263 9637

6 0271 96W

o 0233 3637

0 0 2M 3637

1 00 698 *

00 496 240

00 49 e 240

00 498 240

00 448 240

00 670 312

00 946 46S

00 !363 672

00 ?73 w

6~ 361

3249 w

3W9 429

2769 Im

7W6 322

3792 446

632! 664

t4242 I 106

6W m

4,a.03

4,a.06

4.lE.06

$.4s.03

f 4*.63

I W.06

!m. oa

4m.06

I@. oa

) 4

6

7

8

If

12

te

m

28 O* I 0631 2770

36 0271 0426 9620

M 027t 0426 96W

% 027! 0426 36W

62 0W7 0470 9266

36 027! 0426 3ti

36 0271 0426 96W

33 0271 0429 36W

033 Ow Ow 036 004 0W69

) t.24 O.M Om10 069 OM 0w27

1.14 003 0CW4 Ou Om 0W33

1!.49 007 00226 t.t4 003 OW

6NS663W 1201201 W7600W 7sOO@ 7,3o 0 t!OOW

666 17.W$W IQ i.Q t22 732 t07 7.32 !07 636 0 2060W

w22000m34

sw3wom34

~NT / Smcm DlmNsloNs DECK DIMENSIONS WTERIAPROPERTIES

YYYcone 60 soil

240 t90 f90

LOADING DATA DECK LOADING EARTH PRESSURE WTERIAL STRENGTH PROPERTIESON ABUTMENT

STRUCTURAL PROPERTIESBACKFILL

SOIL PROPERTIES

WSUR WL &EL wmuT WUIVE VVO WA c’ + Ka Ko KO ICU y FY y FSfin 6fl

wd%nwu Asn Q Q @O o c’ Ka Kpmc ms stem *am tiem boss boss bsso

00

Un ~N

fwa Qa 6!33 1022

Sti *d

law I&o o 36 0274 0426 3~ 9m.a 1,62 4a.04 f !6 9W*06 OM 006 0W24 OW 006 0- 4s0 160 O!WO 26 6 03W ‘2mi

No Nwltitltltt2hlh2hl h2h~zz~kW Ltdn w LWFULS ULS S1S SLS Ian@, Im*

64 &46 26M 4.W 063066 OW 626 O@ 628 OW 628 0 046 OW 24,73 i6f8 042 6 %33 09!24

16 6!2 N,46 S63 06! 081 t,~ 61t O@ 6!! OW 6tf O 4.02 002 2740 t8m 040 6 94! 0W3

t? 6004077370 OW 060 !,m 7.26 OW 7,26 OW 7.26 0 !.m O@ W,W t646 024 8 334 097W

20 610 f7.04 S61 t.Q t,62 1,97 7.32 06! 7.32 06t 7Q O t.m OW 17,43 12 f7 076 4 9m 09SW

240 !90 190

296 t90 i90

24.0 t90 !90

00 m3 o 628 733a Q8 23W !631 o 33 027f 0426 3= 3W.04 IQ 4s.06 t.t6 9~.03 073 006 OW24 ON 006 0W33 460 f60 01~ 26 6 03W 2 S6t

.00 IM2 672 f f33i !IR 1340 3247 0 33 027t 0426 3W 3m.06 $.m $ 6S*06 !.16 1.2W. W ’072 006 0~ OW 006 00126 160 @O WW 240 0422 2.971

00 766 264 6346 662 !W4 1176 0 96 027! 0428 36W 9tW+04 16 I *.06 ! f6 t,2x.06 ‘t46 006 OW t~ 004 OWIO 4W fm Otw 34 0 0233 3637

mENT I STRUCUE DlmNSIONS DECK DIMENSIONS MTERIMPROPERTIES

w L~ 777tan. cow M Ed

36a i.ml 240 490 190

LOADING DATA DECK LOADINGON ABUTMENT

WSUR WUDL WKEL W~UT WALIVE WD WA cofill

00 49e 240 9796 366 lm9 962 0,

00 62.8 3i2 9924 4m tt33 tfw o

00 628 S12 lm 49! !133 flaa o

00 496 240 7222 320 2t66 !fle o

00 633 9!3 Q 6t0 fa97 Ilw o

EARTH PRESSUREBACKFILL

o Ka Ko Kp60

MATERIAL STRENGTH PROPERTIES STRUCTURAL PROPERTIES SOIL PROPERTIES

No b’ WI W2 tl tlt t2 hl h2 hl h2 h aZZskw LtdnULS ULS SLS SLS Imo$

21 4Q !I,W 2,30 t40 i,40 126 640 OM 640 036 626 14 t,60 OW f149 t713 046 2

22 670 1914 2,20 260 I@ 1.60626 226 796 066 86 14 346 OW t2W li36 042 3

23 7m t916 t.w 2.60 1,60 I.W 647 2.M 646 OW OW t4 946 Om t2W 1636 042 9

24 670 f992 !.W !.20 t.20 !.S0 692 !.W 787 040 627 14 2.30 OW t9w tamom 2

26 7,t0 1479340 !20 !20 t.20 66o !.W 7,40 OW 830 14 160 OW t4@ f76606f 9

wdxnm~xnstem stem stem base base b~so

1,33 006 OW !.18 006 OWW

243 006 0~ !.63 003 003!6

243 006 OWW f66 Om 0W16

t.13 006 om17 136 Ocd Om

113 OM 0W34 t.14 OM Omt

36 0274 0426 36W

363 09s72 24.6 !69 100 36 027t 0426 36W

%63 09072 24,6 189 190 33 027! 0426 9M

966 f.mt 260 100 f90 36 0271 0426 96W

9W 0W42 260 t90 f90 M 0271 0426 9W0

~NT / STRUCTURE Dl~NSIONS DECK DIMENSIONS WTERM LOADING DATA DECK LOADING EARTH PRESSURE MATERIAL STRENGTH PROPERTIESPROPERTIES

5TRUCTUML PROPERTIES

No &wlw2tltltf2hlh2hl h2ha ZZskwON ABUTMENT

SOIL PROPERTIES

Ltdn w LWFBACKFILL

U ULS S1S SLS7Y7 WSUR WL WEL WMUT W~lVE WO WA c’ ~ Ka Ko Kp fcu y FY

Ianos Inne Cow m sod7 FS dNA d Asn w d ~n

m finQQ @O + c’ Ka Kp

2 7.s2 1.W S9S 072 07209t 4rn 063 tf48 434 191 0 2t90w Ow Ow Ow 4

mc

Om Om

ms

240 t90 190

stem dnm 639m

00 67 33 w

btsc base bsse

40 00

&& Sd cd

s

6 W 0271 0426 9W 3 !E.04 !.60 4a.06 1,!6 9W+06 067 003 004W 079 O.m 00!00 l@63WO~3060W3~

9@ l.~ 2.W f.20 120 1.30 6@ 493 1928026 136 0 2M 2,w Ow Ow 00 2 Om Oww 297 fso i90 32.0 67 33 , 676 40 00 36 02@ 04t2 3W7

6

6 3m.a !60 4W.06 1,!6 39S.03 ti4 OM Om t,20 Ou 0WS2 4@ 160 Ot~ W 6 0333 3~

467 !.m 09t 0760760769292M 963 234 617 0 14309! Ow Om Ow 4 Ow Om 236 t89 180 326 67 33 193 40 00 0 360 02@ 04W 99W 3!w+a !60 1.W*06 t,16 1.2K.03 071 003 om7 071 006 0W68 20W 1~ 00229 34 6

9

0263 9637

4.40 I.w 2,fo omo300m 7360s 6W 0s6 7s3 o 0600m Om Ow Ow 2 Ow Oww 240 t90 (90 t@6 67 33 176 40 00 3429 0260 04W 9m

10

6 3m. M 162 4a*06 1,!6 9W.03 063 OM 0.0146 079 004 0W60 ~3WO~30606333~

2~ l.~ !,W OM 036 OW S22 048 922 048 970 0 OW 046 Om Ow Om 4 Om Oww 296 169 189 !67 67 u 4a 40 00 0 33 0296 0466 3392 3W*04 I m 4.=*O3 t.ta 39S+M 02a 006 OWW 023 003 0W70

Is

4W 126 026W S o

am l.m 2.w 060 0600.604 .300w 4W ow 430 0 060 ow Ow Om Ow 2 Om Om 240 190 190 17.o a7 m

0296 3W2

66 40 ‘o o 0 % 027t 0426 36W 9U.04 fao 4W.06 f,!6 93W.03 043 006 Om 043 006 0W70 4@ f600WWW 60333 3W2

t6 4- I,@ 2,74 !@ 034 0.76676 130 676 fW 6S6 O 076061 Ow Om Om 3 Om Om 240 460 t90 00 67. 33 2;4 40 00 6 30 02@ 04t2 3W 20E.04 1.60 !,4s.03 i,la f.lm. oa .093 OM Om 066 Om 0W61 to mom 290 0347 2.W

ASSESSMENT OF SUBSTRUCTURES (BD21/84) WORKSHEET 1 INPUT DATA FILE

DIMENSIONS, MATERIAL AND SOIL PROPERTIES AND LOADS 1I

-.

u

. ... . ,,

ASHE~ SPW FOO~OS

SLDING OF FOUNDATIONULTMTE LNIT STATE STRUCTURAL ELEMENT

BE** PRESSURE BENDNG N THE STEM: ~yWWfSW&= STEM: s- STRESS W STEMLO~ CASEA

SHEAR STRESS N *LO~ CASE9 Ko PRESSURE

BSE RES SLO 8ss REs SLO MMFDN Mu FI F2 S4s MM~ FOS FI F2 Ms4m FOS til v, KO FOS, ti V W FOS K4 M

LOAO - SLO

FoS ~H FOS

FcE FOS ~ SLO FCE FOS mss FOS uLS ULS ULs 1 5K0 ULs ULs ULS 1.5K8 BASE Wn

* 96 so 5953 3405 1.75 56 6619 3494 1.69 2?1 1667 6033 169 354 0 1820 331 120 24@ 4204 502 643 655 0 9s 445 1.45 46 13,73 9s e.ss

4 110 47 3824 2119 1.61 51 4077 2249 1.81 357 210 5012 266 46 0 970 512 171 30 626 6.00 597 3s6 155 247 242 -485 1.23 105 305

5 125 63 5920 2003 29S 66 6283 2116 297 345 200 4232 311 233 0 201 ? 210 197 157 1296 326 597 7t6 O 63 467 1.28 -261 212 177 3.37

7 92 69 10s02 1538 6.S9 62 $1230 1618 694 206 972 1464 291 0 0 690 165 165 0 566 259 267 337 079 214 1.25 -96 312 81 3ss

8 130 56 56S0 3110 162 61 6111 3206 190 293 307 6527 429 0 0 1979 330 255 0 1162 5,52 245 302 061 179 137 -133 1.83 117 2.0s

11 110 56 4537 2699 168 66 500s 2631 177 257 350 1725 391 66 0 t 660 104 259 44 1067 159 570 643 069 552 105 .46 1024 SO 59?

12 t 22 64 12912 4731 256 69 12964 4911 264 317 276 7342 407 0 0 1641 447 259 0 4047 7.01 279 329 065 209 1.34 -436 069 191 2.04

16 140 71 16472 5972 309 75 19432 6298 309 310 193 6861 360 0 0 1432 479 241 0 9+3 751 371 333 1,11 212 175 -63 499 al 50s

19 146 74 11345 2963 3 SO 79 11957 3172 377 330 1.62 10157 372 111 0 16~ 555 236 72 <166 e 70 385 337 t 14 216 178 -111 383 97 4.40

ASHENTS RLSO

SLDWG OF FOUNDAT~ULTMTE LIMIT STATE STRUCTURAL ELEMENT

BEARING PRESSURE BENDING N THE STEM: BENDWG M T= STEM: SHEAR STRESS N STEM SHEAR STRESS N BASELom CASEA LOADCASEB Ko PRESSURE Ka PRESSURE

BSE RES SLO BSE *S SLO MM FDN Mu FI F2 Ms MM~ F 0S, FI F2 MMm F OS wLT w KO FOS. KO V. Ka FOS. K3 * FOS ~H FOS

LO~ ~E SLD F CE FOS RSE SLD FCE FOS mss FOS ULs ULS ULS 1 5K0 ULS ULS ULS 1 5Ka BASE WCH

14 116 43 6211 2776 2.96 46 8724 30s5 265 276 162 1305 273 0 0 863 151 174 0 550 237 371 546 069 347 1.07 .53 7.70 60 6.03

15 92 34 7309 2166 337 37 7659 2426 324 221 2.04 2795 106 0 0 479 584 116 0 306 9.14 37J 254 146 162 229 .41 9.93 66 620

17 122 43 11012 5783 190 43 1165S S3105 1,91 275 055 2816 357 0 0 1301 217 227 0 829 340 554 497 112 316 176 -1 107100 74 a 70

20 149 75 9677 2758 3.5S 61 10461 2936 356 339 t 33 10132 377 61 0 1639 610 239 40 1045 970 270 300 090’ 191 1,41 -116 2.42 85 3 W

~_G~ SLOPWO

SLOING OF FOUNDATIONULTIMATE LIM~ STATE STRUCTURAL ELEMENT

LO~ CASE ABEARING PRESSURE ~;D$~s~ STEM: BENDWG IN THE STEM: SHE~ STRESS IN STEM SHEAR ST=SS N BASE

LOAO CASEE Ka PRESSUREBSE RES SLO BSE RES SLO Mm FDN Mu F1 F2 Ms MMta FOS FI F2 MMM FOS WL T, v, Ko FOS W v Ka FOS: Ka -E FOS -CH FOS

LOAO RSE SLO FCE FOS RSE SLO FCE FOS mss F OS ULS ULS ULs 1,5K0 ULS uLS ULS 1 5Ka BASE WCH

21 118 51 3240 1124 288 57 3540 1220 290 286 350 0040 225 69 451 12s6 624 143 45 986 e 16 204 22+ 092 t42 144 -142 ? 63 78 301

22 13s 60 IO*57 2506 419 67 11116 2630 4.23 298 504 27150 296 232 615 269S 10.10 189 156 2026 1340 t65 2+8 0s5 142 130 -102 312 60 361

23 13B 60 10759 3175 339 67 11453 3292 346 293 444 27150 324 322 945 3412 796 206 219 2541 1069 165 266 069 175 1.08 .74 439 95 341

24 110 48 6432 2620 245 54 6925 2707 256 245 611 6036 354 140 742 2554 2.36 225 92 1901 347 330 438 076’ 261 117 -21 1229 89 3.71

25 117 51 6667 2425 275 55 7~47 2W9 276 267 374 6309 300 179 661 2370 268 191 120 1764 356 416 425 0.96- 275 151 .16 26.91 94 4.72

~NNINO WALLS

SLDNG OF FOUNDATIONULT~TE LIMN STATE STRUCTW ELEMENT

BEARING PRESSURE ~W&N~sy~HE STEM: BENDNG N THE STEM: SHEAR STRESS N STEM SHEAR ST=SS W BASELO~ CASE A LO~ CASE B K@PRESSURE

BSE RES SLD BSE RES SLD Mm FND MU FI F2 Mt MMU FOS FI F2 MMW FOS WL T v. KO F05 KO v Ka FOS: Ka WE FOS ~CH FOS

LO~ RSE SLO FCE FOS RSE SLO FCE FOS ms FOS ULs ULS ULS 1.5K0 uLS US ULS i 5Ka BASE WH

2 121 52 611 529 1.15 61 679 680 100 2E3 362 3518 189 1091 0 6714 052 111 796 4611 0 7e 603 1912 032 1355 0.45 3BI 1,58 54 tl.lo

3 112 48 1170 521 224 53 1217 717 1,70 246 163 9530 793 646 0 9454 100 512 586 6213 153 572 1438 040: 965 0.59 355 135 68 700

6 54 27 353 166 213 31 371 176 211 124 1612 2536 204 295 0 1347 186 127 199 865 293 432 706 0,61 463 093 16t 294 31 15.31

160 69 386 336 114 76 421 348 121 350 251 3559 680 47 0 3506 102 536 29 2138 1,67 675 1476 046’ 696 075 306 1.64 44 11479

48 23 77 54 1.40 31 96 66 145 129 311 462 191 40 0 406 110 123 26 265 +,6210

503 624 061 535 094 245 2.16 28 1906

90 39 133 7% 187 50 167 62 204 232 193 1159 268 0 0 576 20! 170 0 367 316 503 623 081 396 127 B3 6.37 20 16.3713

112 47 264 97 292 56 329 110 298 266 0.37 3087 369 126 0 1910 162 246 64 1211 255 353 545 065 348 101 71 S.65 63 67216

——— .——

ASSESSMENT OF SUBSTRUCTURES (BD21/84) WORKSHEET 2 CALCULATIONS ULTIMATE LIMIT STATE

}

I

r

i,

AS~ENT6 SPRSAOFOOnNOS

SEwCEmlLITY LIMITSTATEOF SOIL SENCWILITY LIMITSTATESTRUCTURALELEMENT

SETTLEMENTOF THEFOUNDATION BENDINGIN THE STEM: KO MOMENT RESISTANCE

o FI F2 F3 MMM

MLOW F OS m P L SLS SLS SLS SLS FOS

1 300 2.21 0.0600 8.14 0.00066 254 97 0 t331 4.53

4 450 2.52 0.0600 10,71 0.00167 200 0 0 663 7.56

5 230 1.33 0.0800 13.01 0.0014 265 96 0 1422 2.98

7 1000 9.72 0.0153 1.57 0.000343 194 0 266 394 3.72

6 300 2.o5 0.1000 1464 0.00178 270 0 0 1234 s 29

11 300 2.34 0.0660 8.46 0.00143 265 45 0 1103 1.56

12 300 1.89 0.0600 9.51 0.00127 271 0 0 1087 6.75

16 200 129 0.0600 9.32 0.00104 253 0 0 950 7.22

19 300 1.62 0.0600 13.19 0.00126 248 76 23 1206 8.42

MmENT6 PILEO

SETTLEMENT OF THE FOUNDATION EENOING IN THE STEM: KO MOMENT RESISTNCE

a F1 F2 F3 MMW

ALOW FOS m P k SLS SLS SLS SLS FOS

14 150 1.06 0.1000 13,68 0.00144 162 0 0 572 2.28

15 150 1.36 0.1000 11.03 0.0012 ~24 o 0 316 6.64

37 50 0,36 0.6000 62.51 0.00916 238 0 0 663 3.26

20 150 0.69 0.1000 16.95 0.00165 251 42 9 1063 9.35

-~ENT6 SLOPINC

SETTLEMENT OF THE FOUNOATION BENOING IN THE STEM: KO MOMENT RESISTANCE

a FI F2 F3 MM~

ALLOW FOS w P k SLS SLS SLS SLS F OS

21 400 2.60 0.0500 7.14 0.00106 t 50 47 2 1005 6,01

22 500 336 0,0600 6.93 0.000668 307 41 130 2139 12.69

23 430 2.93 0.0000 ~fl.72 0,00112 349 73 106 2714 10.00

24 500 4.07 0.0800 9.82 0.00115 296 29 11 2043 2.95

25 300 2.25 0.0500 666 0.000627 254 64 6 feel 3.35

RSTNNINO WALLS

SETTLEMENT OF THE FOUNDATION BENOING IN THE STEM: KO . MOMENT RESISTNCE

Q FI F2 F3 MM~

~LOW FOS pm P A SLS SLS SLS SLS FOS

2 300 2.12 0.0800 11.33 0.000991 615 172 93 4633 0.76

3 150 1.22 0. t 500 78.47 0.0013 1039 35 54 7$66 1.33

6 1000 16.12 0.0229 1.42 0000207 166 172 27 901 2.62

9 300 1.67 0.0600 14.34 0.00217 517 66 0 2233 1.59

10 125 1.95 0.2000 12.85 0.00343 127 27 o 272 1.77

13 150 1.29 0.0600 699 0.00155 179 0 0 384 3.02

16 50 0.37 0.6000 6036 0.0107 246 84 0 1207 2.56

ASSESSMENT OF SUBSTRUCTURES (BD21,W4)

WORKSHEET 3 CALCULATIONS

SERVICEABILl~ LIMIT STATE

I

STRUCTUWL PROPERTIES-MENT I STRUCTURE DIWNSIDNS DECK DIMENSIONS MTERIALPROPERTIES

iYYcone 66 s~

24.0”190 f9 o

240 204 200

240 f07 t90

LOADING DATA

WSUR W ~EL

DECK LOADINGON ABUTMENTW WA co

m

2U9 t261 o

~RTH PRESSUREWCKFILL

+ Ka KO KPm

36 027t 0426 3S90

20 0361 0631 27m

34 0271 0428 3M2

MTERIAL STRENGTH PROPERTIES SOIL PROPERTIES

No W WI W2 11 tlt t2 hl h2 hl h2 h aZZskW ULSSLS mS

1 e20 !7302,W OW OW f.024,96 966 731 132 Sa O t.020W

4 427 !4Q 2.44 091 09t 076 6@ 062 6S2 Om 861 0 076046

6 e26t1209s owomf.m6m 226 764 130 e94 o tmtm

7 906 1664 1,07 oof 09! oet 809 om 6m om 60 0 2m om

e 649 1624 !.S3 162 162 1220t4 Om 0t4 Om 914 0 l,220m

If aw 17,07 lw 01607800$ 7.01 oet 701 061 762 0 09! om

12 6mw~2.20 fwomo76 amom em om em o 076 040

I@ 6ma94a9w t20t20t.m7.6oom 7,60 om 760 0 itoom

19 o~ 17.@9m 162 i.62 t.22 732 to7 7.32 t.07 836 0 2.060m

w Ltdnlanes

16t0 !824 O@ 4

WWUT WMIVE dwfl~nw~tindom tiem Slm b-so base bs$c

063 006 ootm 066 om oofm

ow om oofm 0s7 om ooim

076 004 oofm 092 ow ootm

066 004 om4 06s 0.03 om33

t 49 007 omlo f.fg 0.0? omfo

Kp*d

%637

2770

asw

&we

am2

a637

amo

aaw

a637

c’

00 *9 2U

00 409 240

00 409 240

00 409 240

00 439 218

00 663 266

00 929 466

00 IW9 667

00 760 372

m 4W

3249 349

36m 420

27@ 392

?M 296

3792 m3

632~ Sm

!4242 !166

~6 S73

o

6

0

6

6

6

6

0

0

14as@ 094 2

lt20 4307 047 2

3249 349 6

27M 1663 0

O.wf

02s3

0.672

0s

0263

0271

0 2s3

o 2M

13M 1044 027 2

12.79 2866 061 2

964 !m!

sm 06990

3M 09179

366 fmt

a6? 09762

$66 09700

236 189 189

29e 176 190

446 W2 o

2619 !249 6

IM7 1248 0

97W 23m o

22w 2w6 o

2027 t4& o

36 027! 0426 9660

36 0271 0428.3~

32 0307 0470 92a

36 0271 0428 9~

% 0271 0428 3W

33 0271 0426 3=

236 !90 190

240 t76 t90

240 t90 190

240 t90 $00

066 Oa O- 066 004 om49

t.24 OW Omto 0,69 004 0W7

!.14 OQ 0W4 Ow Om ocm3

!.49 007 owe 1.f4 006 Om

mom30mm34

e76 am Oomo 36

6o02mooam34

m2m30m36

~NT / STRUCTuRE Dl~NSlmS DECK DIMENSIONS MATERlmPROPERTIES

No b’wl@llllt12hlh2hl h2ha ZZskw Ltdn w LWULS ULS SLS S1S

7YY18nas IM9

14Com ml sod

646 2666 4,W 046 02S Orn 62S Orn 62S Orn 628 0 O= 003 24,73 f6t6 042 6 933 00424 24.0 190 t90

LOADING DATA

WSUR WUDL WEL

DECK LOADING EARTH PRESSURE WTERIAL STRENGTH PROPERTIESON ABUTMENT

STRUCTURAL PROPERTIESMCKFILL

WO WA c’ o Ka Ko Kp fcu y FY y FS Mu=nwutin611 60 mc ms slom atom rnsm baso bsso boso

SOIL PROPERTIES

00 m! 462

00 tm 6 493

00 1327 6Q

00 760 *

!693 IW o 34 027i 0426 3690 3m. c4 !.60 4.=*O6 1.f6 9~*06 Om 004 om24 060 006 Om

16 &f2 2046 9S6 08! 081 t.~ 6it Om 61t Om 611 0 +.02 Om 2740 tOm 040 6 %41 0934$ 240 !90 190

17 6m 4077 a70 OW 060 t,m 7,26 Om 7.28 Om 7,26 0 I.m Om W66 1846 024 8 334 097m 296 (90 190

20 6t0 t704 96! tQ f.Q 1.37 7,32 06t 7W 06! 7,92 0 tm Om 1749 f217076 4 903 096m 240 190 t90

23s6 2!06 o 36 0271 0426 $~ 9ti*M 102 4W.04 1.16 9~*06 073 O& om24 Ow 006 Omm 4s0 160 Oi~ 26 6 0= 2.661

tm mom 240 0422 2.wf

4m {m 0!002 34 0 0.2s9 a 637IW4 f2m o 36 027t 0426 3~ 91@.04 I 6 !.s.06 f t6 I 2E.06 t46’ 006 Om !.32 Ow omfo

M-NTS SLOPING

ASL7TMENT/ STRWWRE DIWNSIONS DECK DIMENSIONS WTERIA

NoPROPERTIES

bwlw2tl lltt2hlh2hlh2 h aZZskw Ltdn w LWULSULSSLSSLS

Y7718.9s Ian* cone M soil

2! 4@ il.m 2.30 t.40 t40 1.26 640 064 640 066 626 14 1,60 Om f149 4713 048 2 9& IOmf 240 100 t90

22 am ta!4 2,20 260 !,M I.W 626 226 7.94 066 860 t4 9460m t2m f836 042 9 963 09s72 246 le9 !90

29 r.m taf6 \.m 2m [m IW 647 266 B46 om 93414 s460m f2m t6X 042 9 96 09672 246 !69 t90

LOADING DATA DECK LOADINGON ABUTMENTWO WA c’

611

!N to37 o

EARTH PRESSUREWCKFILL

4 Ka Ko Kpfill

34 027t 0426 9690

WTERIAL STRENGTH PROPERTIES STRUCTURAL PROPERTIES SOIL PROPERTIES

WSUR WUOL WKEL W~W WM lVE

3796 362

W24 497

Im 419

R22 9f8

m33 4n

dNA d ASTL d~ d ASTLslom stwm mom btso ba$a baso

133 006 Om f,fe 006 Om

2.49 004 Om !.46 Om om16

249 006 oom2 1.66 o~ omfe

00 409 240

00 614 M2

00 614 m

00 489 240

00 674 262

lf33 Ila o

1133 1!66 o

36 027t 0428 3~

24 670 f3Q l.~ 120 120 t.~ 6W 136 7.67 040 827 !4 2WOm !9W t670 070 2 97 I.ml 260 f90 t90

26 7.60 t4. m a40 1.20 1.20 f,20 6m IW 7.40 060 830 u i,m om 14m t766061 3 a9 om62 260 190 t90

2176 !164 o 34 027f 0426 3~ 1.t3 006 omt7 1.s6 003 omm

1.t9 ao4 O- t.t4 006 OmllW tms o

m- WALLS

~N / STRUCTURE Dl~NSIQNS DECK DIMENSIONS MATERIMPROPERTIES

No bwlw2tl tllt2hlh2hlh2 h aZZskw Ltdn w LWFULSULSSLSSLS

7YYl*n96 lane COm M sod

2 7.~ I.m a96 OR 072 091 4.~663 !!,46 t64 !9!2 O 2f30m om om om’ 4 om omm 240 t90 t90

3 9m f.m 2.W 1.20 !.20 I.W 660496 t326 026 t346 O 2402W om 002 om 2 om oomo 2S7 160 !90

6 467 f.m 001 078076076929266 SW 236 617 0 i.4909t om om om 4 om ow 296 f60 t69

LOADING DATA DECK LOADINGON ABUTMENT~ WA c’

66

00 6

EARTH PRESSURE~CKFILL

+ Ka Ko Kp60

36 0271 0426 am

MATERIAL STRENGTH PROPERTIES STRUCTL2WL PROPERTIES SOIL PROPERTIES

WW WALIVE

w 40

676 40

!m 40

t76 40

46 40

as 40

224 40

dwtitinwu=ntiam tiom ctom base baso bas~

0.s7 o~ oolm 0.79 006 ootm

f,!4 Oa om66 1.20 006 0.-

0 7! 004 0.0037 0 7t 0.06 0.C066

QQ m+& ●b

1026 WO 0~ W

4m Im omoo w

2cm lm a@29 66

m2m20mmao

4m 126 02m2 33

c’ Ka m$@ ndt

6 0- aooo

6 0933 aooo

6 02s3 a 637

6 0= aom

o 0.296 a=

6 o,am aw32

o 0.M7 2.m

00 67 M

32.0 e7 33

32.6 67 33

1W6 67 33

t67 67 33

17.0 67 33

00 67 33

00 6 m 02a2 0412 36Q

00 0 s9 02m 04m 99m

9 440 I.m 2.10 om 0s 0.60 7.36030 6m 0s6 7.s4 o osoom om om om 2 om oomo 24.0 t90 t90

to 2.W 1.60 !.00 036034030 a22 046 922 046 9m O 030046 002 om om 4 om oomo 236 f69 189

Is 3m too 2.momomo.m4.som 430 om 4% o oooom om om om 2 om oocm 24.0 f90 tOO

tO 4W l.m 2,74 1.03 036 076 &m t.W 67S 1.3 em O 076061 om om om 3 om om 24,0 !60 t90

00 6

00 0

3s9 02m 04m 99m 9W.W t.m 4.m+06 t.f6 aM.06

3W.M +.60 4.W.06 1.!6 aW.06

9U.04 1.a2 4.mE. os !,46 aW.04

2.07E*@ t.m t.4S.06 !,16 1.t7E *04

069 O,M 0,0t46 073 O.M O-

028 006 Om 029 0.06 Om

049 006 0- 043 0.06 Om

OM 006 Omw 0s6 O.m Omf

33 02M 0464 93m

00 0 36 0271 0426 9M0

00 6

ASSESSMENT OF SUBSTRUCTURES (BD21/93) WORKSHEET 1 INPUT DATA FILE

DIMENSIONS, MATERIAL AND SOIL PROPERTIES AND LOADS (

I

_— ---.. , ..

ULTWTE LWm STATE STRUCTU~ ELEMENTBENDNG N THE STEM:Ko PRESSURE

Mu F1 F2 Ms MMti $ 0s

ULs us ULs 1 5K0

6033 189 354 0 1818 332

SL~NG OF FOUNDATDNLO~ CASE A

BsE RES S10

LOM RSE SLO FCE FOS

99 50 5953 3405 175

BWNG PRESS= BENDNG N THE STEM:m PRESSURE

FI F2 MMM F OS

us ULs ULs 1.5KS

120 240 1202 502

171 30 626 8.01

SHEAR STRESS N STEMLO~ CASE B

8SE RES

RsE SLo

5a 6e14

-E FOS: ~ FOSEASE WH

46 +377 98 6.5s

-509 117 202 2.95

-208 2.89 152 3.01

SLO

FCE

395s

2535

2343

2035

3623

MNFON

%s FOS

2?1 1668

Ml vKO FOS Ko V.ti FOS KSFOS

+.671

4

5

1

e

11

12

16

19

843

597

591

267

245

570

2?9

371

385

655 098 445

3s6 1.55 247

748 0.s3 46?

337 079 214

302 001 179

843 069 552

329 005 209

333 1.11 212

337 ~.f4, 216

145

242

1.28

1.25

137

1.05

1.34

1,76

1.78

118 47 3S24 2119 1.81 105 362 2.07

329 210

207 967

293 307

257 350

318 275

315 191

331 1.s1

5012 260 46 0 916 51361 4683

72 6567

136 13858

71 6SS9

197 157 f294 321

185 0 566 2.59

255 0 ‘1181 553

259 43 1087 1.59

125 63 5920 2003 296

92 69 10602 1538 6.s9

130 56 56s0 3118 102

280

681

1.90

4232 311 233 0 20! 3 210

1484 291 0 0 609 165

6527 429 0 0 1976 330

.104 Zee e3 3s6

.t33 1.84 117 2.06

-49 976 00 592

-443 0,68 192 2.03

110 56 4537 2699 1.6s

122 64 12912 4731 2.58

140 71 1s412 5972 3.09

146 74 11345 2683 3.60

3313

5483

6694

3428

1725 397 66 0 1659 104as 6559

9a 17006

97 24750

87 12900

190

7342 40? o“ o 1640 440

6861 3s0 o 0 1432 4 ?9

10157 372 111 0 !827 5.56

310

370

375

259 0 4046 ? 02

241 0 913 7.52

236 72 1187 e 71

-101 4.08 as 4.76

.118 3,60 96 4.31

ULTMTE LIMIT STATE STRUCTUN ELEMENTBENDNG N THE STEM:Ko PRESSURE

Mu FI F2 Ms MM~ FOS

ULS MS ULs 1 5K0

1305 273 0 0 862 151

2795 t 86 0 0. 478 584

2616 357 0 0 * 300 217

10132 377 61 0 1637 619

BENDNG N THE STEM:Ka PRESSURE

F1 F? MMM F OS

ULs ULS ULS 1 5Ka

174 0 549 237

SHEAR STRESS W STEM SHEAR STRESS N BASESLDNG OF FDUNDAT~LOAO CASE A

BSE RES SLO

LOAO RSE SLO FCE

116 43 8211 2776

92 34 7309 2168

122 41 11012 5763

149 75 9a?7 275a

BEARM PRESSURELOAO CASE B

BSE RES

FOS RSS SLO

2.9a 55 10246

3.37 4a 9933

1.90 5s 1534?

35a 91 11495

SLO

FCE

MU FON

%ss FOS

279 161

223 202

275 055

340 1.32

WL T VKO FOS Ko w Ka w FOS *CH FOS

BASS WH

-60 a.a5 71 5.e4

-50 a 32 a9 597

F OS

3.20

3 a6

2.36

356

37* 546 060 ’347

371 254 1,46 162

554 497 112 316

270 300 090 191

1.07

229

*.76

1,41

3200

2573

649S

3231

lla o 305 915

0 320400 73 a.7a

-119 2.34 aa 327

227 0 a2a 340

239 39 1044 9.70

ULTMTE LWIT STATE STRUCTUW ELEMENTBENDING N THE STEM:Ko PRESSURE

Mu FI F2 Ms MUM FOS

ULS ULS ULs 1 5K0

awa 225 69 4a5 1300 619

271W 29a 232 al 1 2689 10 to

27150 324 322 940 3405 79s

6036 354 f40 75* 258! 236

6331 300 379 669 2378 2 S6

BENDING N THE STEM:KS PRESSUW

F1 F2 MMU FOS

ULs UL S ULS 1,5Ka

SHEAR STRESS N STEM SHEAR STRESS W BASESLIDWG OF FOUNDATDN10AOCASEA

BSE RES SLOLO~ RSE SLO FCE

116 51 3240 1124

13a 60 10519 250a

I 3a 60 10763 3175

BEARWG PRESSURELOAO CASE B

8SE KS

FOS RsE SLO

2 aa 66 3970

4.19 73 I 16aa

339 74 12060

2.45 63 7831

275 60 76a4

SLO

FCE

1435

MN FON

mss FOS

2aa 34a

297 5.05

293 444

246 610

tiT v. KO FOS, Ko v Ka F09 Ka * FOS ~NCH FOS

BASE WH

-~49 f.57 79 2.95

-101 3.21 69 362

FOS

2.7?

3 al

3.12

2.41

2.71

143 45 999 a 06 204 221 092 142

1B5 21e o.a5 142

la5 266 069 175

330 43a 0.76 2S1

41a 425 098 275

J.44

i.30

I,oa

1.17

151

21

22

23

24

25

3069 1a9 156 2020 1344

-72 4.4? 95 343

-23 ~1.35 70 3.6s

-19 23a2 94 4.a9

3a62 206 219 2534 1072

110 4a 6432 2620 316a 225 92 190a 316

268 374 191 120 1772 3574*7 51 6aa9 2427 2a27

~NWNO WALLS

SL~WG OF FOUNDATONULTMTE LNIT STATE STRUCTURAL ELEMENT

LOAO CASE A

BEARING PRESSW BENDING IN THE STEM: BENDNG M THE STEM SHEAR STRESS IN STEM SHEAR STRESS M BASELO& CASE B

BSE RES

Ko PRESSURE n PKSSURESLO BSE =S SLO MN FON Mu F1 F2 Ms MMW FOS. FI F? MMm F OS WT w

LOAO RSE SLO FCE FOS RSE

v. Ko FOS: KO V. Ka FOS Ka FOS -H FOS

SLO FCE FOS ms FOS ULS ULS ULS 1 5K0 ULS WS ULS 1 5Ka BASE

2 121 52

. -H

611 529 t 15 61 679 6ao i.oo 2a3 362 351a 1a9 1091 0 6714 052 111 796 4811 076 603 19t2 032 1355 0.45 3al 1.ss 54 11.10

3 112 4a 1170 521 2,24 53 1217 747 t,63 248 1.a3 9530 793 a46 o 9454 100 512 5Ba 6212 1.53 572 1438 0.40 985 0.59 355 1.35 as 7.00

e 54 27 353 966 213 31 371 244 1,52 124 1812 253a 204 295 0 1347, I aa 127 199 a65 293 432 706 061 463 0.93 1%1 2.94 31 15.31

9 160 69 38a 338 1.14 70 424 430 o,9a 35a 251 3559 eao 47 0 353a 1.02 536 29 213a I a~ 675 1476 0 4a a9a 0.75 306 1.64

10 4a 23 77 31 96

44 1%.47

54 140 107 090 129 311 4a2 191 40 0 4oa 1 le 123 26 265 I az 503 a24 061 535 094 245 2t6 2S 19.0s

13 90 39 133 71 ~.a7 50 167 123 t.36 232 1,93 1159 268 0 0 576 201 170 0 367 3.16 503 623 0 a; 39a 1.27

la 112 47 2a4 97

B3 a 37 2a ~a37

2.92 5a 329 222 l,4a 26a 0,37 3oa7 3a9 12a o 1910 162 246 a4 1211 255 353 545 065 346 1.01 71 5.95 63 a,72

ASSESSMENT OF SUBSTRUCTURES (BD21/93) WORKSHEET 2 CALCULATIONS ULTIMATE LIMIT STATE

(

-~ENT6 5P- FOOnN05

SE~CENILITY LIMIT STATE OF SOIL SERMCEABILITY LIMIT STATE STRUCTU~L ELEMENT

SETTLEMENT OF THE FOUNDATION BENOING IN THE STEM: KO MOMENT RESISTANCE

Q FI F2 F3 MM~

ALOW FOS pm P L SLS SLS SLS SLS FOS

1 300 2.21 0.0600 0.13 0.00088 254 97 0 1330 4,54

4 450 240 00600 10,67 00017 200 0 0 662 7.56

5 230 1.40 0.0600 1316 0.0014 265 96 0 1421 2.98

7 1000 961 00153 1,58 0.000345 194 0 206 394 37~

6 300 2.o5 01000 14,64 000178 270 0 0 1233 529

11 300 2.33 0.0660 e 49 0,00143 265 45 0 1103 1,56

12 300 1.89 00600 9.53 0,00127 271 0 0 f 087 6.76

16 200 1 2? 0.0600 9.45 0,00105 253 0 0 949 7.22

19 300 1.61 0.0800 13.25 0,00129 246 76 23 1205 6,43

~~ENT6 PILEO

SETTLEMENT OF THE FOUNOATION BENOING IN THE STEM KO MOMENT RESISTANCE

a FI F2 F3 MMM

ALLOW FOS m P A SLS SLS SLS SLS FOS

14 150 1.07 01000 1397 0,00144 t 62 0 0 572 2.28

15 150 1.35 0.1000 11.13 0,00121 i 24 0 0 316 8.64

17 50 0.36 0.6000 62,43 0.009t6 230 0 0 663 3.26

20 150 066 0.1000 1700 0,00166 251 42 9 1063 936

--ENT65LOPIN0

SETTLEMENT OF THE F OUNOATION BENOING IN THE STEM KO MOMENT RESISTANCE

Q I FI F2 F3 MMM

ALLOW F OS ~Q P k SLS SLS SLS SLS FOS

21 400 278 0,0500 719 0.00107 150 47 2 1010 791

22 500 336 0,0600 6.92 0000667 307 41 130 2132 12.73

23 430 2.94 0.0600 11,71 0.00112 349 r3 106 2707 10.03

24 500 4.07 0.0800 9.63 000115 296 29 11 2050 2.94

25 300 2.24 0.0500 6.69 0.000626 254 64 8 1869 3.35

WNNINO WU

SETTLEMENT OF THE FOUNDATION BENDING IN THE STEM. KO MOMENT RESISTANCE

Q FI F2 F3 MMM

ALLOW F OS No P A SLS SLS SLS SLS FOS

2 300 212 0.0600 1133 0.000991 6?5 372 93 4633 076

3 150 $22 0.1500 +847 00013 1039 35 53 7J67 1,33

6 1000 16,12 00229 1.42 0000207 i 65 172 27 900 262 ‘

9 300 9,67 0.0600 14.34 0,00217 517 66 0 2233 159

10 125 195 0,2000 12.65 0.00343 427 27 0 272 177

13 150 129 00600 6.99 0.00155 176 0 0 364 302

16 50 0.37 0.6000 6036 0,0107 246 64 0 1207 256

ASSESSMENT OF SUBSTRUCTURES (BD21}93)

WORKSHEH 3 CALCULATIONS

SERVICEABILITY LIMIT STATE

APPENDIX C. E-PLE ASSESSMENT: RETAINING WALL

1 STRUCT~E DETAILS

Name Substructure No. 3

Type Cantilever retaining wall on spreadfootings with shear key, retaining PFA

Dimensions Shown in Fig Cl, attached

2 LOADINGSLoads for foundations are unfactored in accordance with BS8004:1986 c1.2.3.2.4.1. Wind loading is ignored. BA 34/90cl . 4.2 indicates also that factors of safety can be relaxedwhen assessing substructures and foundations. In addition BD21/93 cl. 5.10 indicates that assessment loading willgenerally be limited to dead plus superimposed dead and typeHA loading only. The full HA loading in accordance with BD21/93 cl. 5.21 is applied. Reduction factors given in BD21/93 cl. 5.24 are not applied to the HA loading for thepurposes of substructure and foundation assessment.

For a retaining wall which is constructed parallel to thehighway and embankment the assessment is performed on a metrerun of wall. All applied surcharge or highway loadings areconverted to an equivalent uniform pressure to take account ofthis. For this reason the lane factor reduction is notapplied to the appropriate values of UDL and KEL in accordancewith BD 21/93 cI.5.6 and 5.7.

2.1 =ankment

- Dead PFA backfill assume ~fti= 16 kN/m3

- Surcharge Uniform surcharge due to sloping backfillis assumed to be equivalent to the weight ofembankment above the retaining structure.

w~m = ~ftix equivalent height of embankmentabove retaining wall

=16x2 = 32 kN/m2

- Highway Assume Standard HA UDL and KEL for limitingcondition of loaded -embankment length = 50mBD 21/93 c1.5.21 and 5.22

UDL = 24.43 kN/m (limiting condition)per 3.65 lane width (see Fi~re 5/1 of BD21/93) .

Road width = 7.3m; from Table 5/1 of BD 21/93No. of notional lanes (nk) is 2. The uniformsurcharge is:

wUDL = UDL n~-= 6.69 kN/m22 X 3.65

W- = 120 kN per lane over two lanes

= ~. x 120 = 32.87 kN/m22 X 3.65

‘ALWE = W~L + W= = 39.56 kN/m2

2.2 Structure

- Dead Weight of bridge deckWD= O, since there is no deck

Weight of wall excluding shear key (Fig Cl),wAB~ = w, ~- [b’t2 + tlh2ti+ tlhlti]

where b’ = 9.5 m width of abutment base slabw, = 1.0 m length of abutment base slabW* = 2.8 m width of heelt, = 1.2 m abutment stem thicknesst2 = 1.3 m base thicknesshIti= (13.55 - 4.95) = 8.6m above gwlh = 4.95 m depth below gwl7:: = 23.70 kN/m3

W*Bm= 678.06 kN

- Live There is no live loading contribution apartfrom the embankment highway loading, seeSection 2.1.

2.3 Summary of dead and live loads acting on retaining wall

wUDL = 6.69 kN/m2w = 32 kN/m2W:mm= ow= = 32.87 kN/m2wABW = 678.06 kN/m2

3 EARTH PRESSURE COEFFICIENTS FOR THE BACKFILL (K,t KOt KP)

For PFA backfill BD 30/87 cI.5.4.3 recommends,

K, = l-sind’fti= 0.333l+sin@’rti

K= l-sin@’fW = 0.500

2

% = l+sind’fd = 3.000l-sin@ffl’

It should be noted that sloping backfill is handled explicitlytherefore the coefficients are calculated for horizontalbackfill behind the wall.

Assume wall friction 6 = O, wall adhesion CW = O.

Km = 2(K.(1 + cW/c’))’n and

For backfilled retaining wallsthe following coefficients are

%= 2(%(1 + cw/c’))l~

BD 30/87 c1.5.3 recommends thatused:-

SLS ULS

Structure K. 1.5K0 **

Soil % %

** It should be noted that BA 55/94 c1.3.2 advises using 1.5K=for ULS. For cohesive backfills Ku and Kw are used to modifyearth pressures acting on wall.

4 ASSESSME~

The substructure is assessed for the following four limitstates namely ULS and SLS for both soil and substructure.

Adoption of safe bearing capacities for foundation designshould avoid unacceptable settlements and tilting of thestructure.

5 ULTIMATE LIMIT STATE (ULS)

5.1 ULS of soilThis limit state correspondsmodes (BD30/87 cl.5.2.4.1)

+ sliding

to the following four failure

+ failure of the foundation soil iebearing capacity failure

* overturning

+ slip failure of the surrounding soil

The principles of analysis are based on CP 2 (1951) and BS8004:1986.

For ULS the following assumptions are made;

+

+

+

5.1.1

no drainage behind wall, ie. high V1

excavation in front of wall to lm below ground level,ie. passive pressure neglected in top lm of ground

worst credible load combination is applied

Resistance to sliding (ULS)

Abutment foundation is checked for sliding using the equationfrom BS 8002:1994 cl.4.2.2.3

r = ~’tan 6b= 0.75 a’tan 0~

where ~ = base resistancea’ = effective mean normal stresstan6b = shear strength at the interface soil

foundation

In addition the resistance developed by the depth of the shearkey, z*, is also taken into account as is the depth of groundin front of the wall, z.

The following load combinations need to be considered for theworst condition:-

(a) embankment surcharae load + embankment dead load +abutment dead load.

Pressure on abutment base,

= (385.28 + 85.79 + 254.04 + 244.58 + 89.6)/ 9.5

= 111.50 kN/m2

Boreholes BH 6121R/1 to 3 show stiff to very stiff lowplasticity Boulder Clay (Glacial Till). Table 2 BS 8002:1994for low plasticity clay gives: @’=30 and cohesion c’= 5kN/m2(see CIRIA 204 Section 5.3)

thus 7. = 0.75 o’tan 30

= 48.28 kN/m2

Base area of abutment foundation = b’wl~ depth of shear,keY z~land depth of ground in front of wall, z, as shown on Flg Cl.Resisting force to sliding per metre run 1S therefore~

4

= 1169.66 kN

Sliding force F, per metre run is,

2 + 4K, (Tin-T.)(hmF, = *K, Tfti‘lti + ~)2 + *K4 (~d-~.) Z&*

= 153.87 + 31.44 + 191.60 + 123.55

= 521.15 kN

FOS to sliding = Resistance % = 1169.66Sliding F, 521.15

+ Z*)

= 2.24

CP 2 (1951) rewires FOS 2 2 The structure is thereforeadepate against sliding.

(b) embankment surcharue load + embankment dead load +abutment dead load + highwav live loadinq

Resisting stress to sliding, r~ is the same as (a) plus anallowance for highway live load component on the base of thewall = W~~m = 39.56 kN/m2

Tb = T,+ WA~w~ 0.75 tan 30 w2/b’

= 53.33 kN/mZ

Resisting force to sliding per metre run is due to baseresistance plus the resistance due to the shear key and groundin front of wall;

= 1217.63 kN

Sliding force per metre run is equivalent to case (a) plus thehorizontal component of highway surcharge;

F~ = F, + K, WA~w~ (h,ti+ h2ti+ ~) + Ka W*~W~ Z*

F~ = 521.15 + 195.57 + 30.30

= 747.01 kN

5

FOS to sliding = Resistance % = 1217.63 = 1.63Sliding F~ 747.01

CP 2 (1951) reguires the FOS 2 2 the structure is thereforeadeguate against sliding.

5.1.2 Bearing pressure (ULS)

From ground investigation data boreholes BH 6121R/1 to 3 showstiff to very stiff low plasticity Boulder Clay (GlacialTill) . An allowable bearing pressure of 150 kN/m2 is quoted inthe desi n calculations, and an ultimate bearing capacity of

7450 kN/m has been assumed.

A check of this ultimate bearing capacity was carried outusing Meyerhof; where pO is mean effective stressN. = 40 N$=30 NT= 22 (Tomlinson, 1975; Fi~re 2.11)and assuming pO = 19 kN/m2

then qWT = CrNC +’PO (Nq-l) + hf~m

= 1397.9 kN/m2This confirmed that a worst credible value of qu~ = 450 kN/m2was appropriate.

Worst credible load on foundation from Section 5.1.1 is o,.

Mean bearing pressure ab = C. + WALw~w*/b’

= 123.17 kN/m2

FOS against bearing capacity failure = gmT = 450 = 3.65ab 123.17

CP 2 (1951) reguires FOS 2 2 the structure is thereforeadeguate under mean bearing pressure

Checking allowance for localised distribution of bearingpressure beneath foundation;

q- = a, (l+6e/B)

where e = B/6 (i.e thrust falls on middle 1/3 rd)

= 2 X 123.17 = 246.34 kN/mZ

Therefore FOS = ~ = 1.83246.34

6

CP 2 (1951) reguires FOS 2 2 the structure is thereforeinadequate under the maximum local bearing pressure

5.2 ULS of structural element

At ULS the structure can fail by;

+ bending of the stem

t shear of the stem

+ shear of the base.

For the assessment of the stem it is assumed that the lateral“pressure is based on no wall friction (CP 2 c1 2.435, 1951).In addition allowance for any earth pressures in front of thewall are ignored. Earth pressures generated by the backfillitself are factored in accordance with Section 3 as follows:

Case 1, 1.5K0 used as recommended by BD 30/87 cl. 5.3.2

Case 2, 1.5Ka used as recommended by BA 55/94 cl. 3.2

These same factors are applied to the live loads as given byTable 1 of BD 37/88. This clearly is over-conservative andmight be relaxed in some assessment cases.

Wall adhesion CW = O and K= = #Ka, see Section 3

5.2.1 Wall moments (ULS)

For ULS the worst moment distribution on the stem is due toembankment dead load + embankment surcharge + abutment deadload + live load (assuming an eccentricity of 1 in 500)

Case 1, Usinq 1.5K0

Lateral pressure at top of stem,PI = 1.5 KO (W~ + W~n) - 2 cti(l.5KO)

Lateral pressure at gwl on retained side,P* = PI + 1.5 & Tftihlti- 2 cti(l.5KO)

Lateral pressure at base of stem,P~ = Pz + 1.5 & (~fti--TW) hm - 2 cti(l.5KO) + VW h~

Hence force due to pressure above gwl,FI = (Pl + P2) hlti/2= (45.01 + 139.54) x 8.6 / 2

= 793.60 kN/m

This force has been assumed to act at hti + 0.5hl* = 9.29 mabove base slab. This lever arm is known to be over-conservative.

7

And force due to pressure below gwl,Fz = (P2 + P~) h2ti/2= (139.54 + 202.42) X 4.95 / 2

= 846.40 kN/m

Similarly this force has been assumed to act at 0.5hti abovebase slab = 2.48 m

Case 2, Usina 1. 5K,Using similar equations to case 1, except with KO replaced byK,, the following forces are calculated:

FI = 512.33 kN/m

F2 = 588.27 kN/m

Taking moments at base of stem; let E be the overturningmoment caused by the dead weight of the wall due toeccentricity. For a wall 13.55m high the eccentricity, e, is13.55/500 = 0.0271m assuming a tolerance of 1 in 500.

E = e X WABm /wl

= 0.0271 X 678.06

= 18.38 kNm/m

Maximum moment at base of stem, Mmax, is given by:

Therefore for case 1,L = 9454.05 kNm/m

and for case 2,L= 6213.40 kNm/m

For calculating the ultimate moment of resistance of the stem,~, available details of the reinforcement are limited. It hasbeen assumed that compression reinforcement is present and A, =A,’= .88% of concrete section area. From BD 44/90 cl. 5.3.2.3,using the notation in this report, ~ is given by the formula:

w= (0.6fCu/7u) w, X (d~A~ - 0.5X) + f,’A,(d~AS~M - d’~m)

Assuming fCU= 3 x 104 kN/m2, fY = 4.6 X 105 kN/m2, x = 005dNAmMf

f,’ = = 333 x 103 kN/m2

(T- + fy72000000)

Tm = 1.5 and ~m = 1.15 are from Table 4a of BD 44/90 cl4.3.3.3 and therefore,

8

u = (0.6 X 3 X 104/1.5) X 0.5 X 1.14 X (1.14 - o.29)+ 333 x 103 x 0.0088 x 1.14 x (1.14 - 0.04)

w = 9530.78 kNm/m

The stem therefore has FOS = 1.01 for Case 1 and 1.53 for Case2 and thus satisfies ULS in bending for both cases.

5.2.2 Shear stress in stem (ULS)

From BD 44/90 c1.5.7.3.2 and 5.4.4.1 the shear stress, v, atany cross section is given by the equation;

v= V/(wld~~m)

where shear force, V = FI +’F2w,= unit width

The criteria given in BD 44/90 cl. 5.3.3.2 is that v shouldnot exceed the ultimate shear stress in the concrete,

V* = (0.24/Tm.)(lOOA,/(w,dNAm))ln(f..)lD

‘or ‘Tmv = 1.25, Vti= 571.92 kN/m2.

For the stem there are two cases to check because of the useof either KO or K,:

For Case 1: 1.5 x KO

v= (793.60 + 846.40)/1.14 = 1438.59 kN/m2/m

For Case 2: 1.5 x K.

v= (512.33 + 588.27)/1.14 = 965.44 kN/m2/m

The stem is therefore inadequate for shear (ULS) for both case1 (FOS = 0.40) and case 2 (FOS = 0.59). It was not possibleto check accurately for adequate shear reinforcement becauseof the lack of information on reinforcing detail. It must benoted that a factor of 1.5 has been used throughout on deadand live loads; unfactored live loads would probably have beenused in agreement with the assessment authority.

5.2.3 Base and punching shear (ULS)

In addition to shear stress in the stem, it is necessary tocheck the shear stress on the wall base in accordance with BD44/90 c1.5.7.3.2. The shear strength of the base is governedby the more severe case of:

9

4

+

For basebase has

shear along vertical section at a distance equal tothe effective depth from the face of the loadedarea, BD 44/90 cl. 5.4.4.1

punching shear around the loaded area, BD 44/90 cl.5.4.4.2 applies, for a critical section on aperimeter 1.5d from the boundary.

shear a uniform pressure distribution beneath thebeen assumed.

Vw = Ob WI (b’-w2+0.5t1)- WI t, (~@Nc hlti+ (~~NC -Tw)h2ti)

vpch= ‘1 ‘1 (~CONC ‘lti + (~~NC ‘~W)hM)

Given that dN*~~~ is the effective depth of the base slab~ then

v = v- /wldN*~~~or Vpub/ wl (2 x 1*5 ‘NASASE + ‘1)

= 355.00 kN/m2 or 68.35 kN/m2

In both cases the ultimate shear strength Vtihas beenrecalculated as 478.82 kN/m2 for the base following the~rocedure in section 5.2.2. For base shear, FOS = 1.35 and~or

5.3

For

base punching

SERVIC~ILITY

SLS assume;

shear, FOS = 7.03.

LIMIT STATE (SLS)

full drainage and developed groundwater profile

worst credible load combination in service

5.3.1 Allowable bearing pressure (SLS)

An allowable bearing pressure of 150 kN/m2 is quoted in theoriginal design calculations and has been used in theassessment.

Thus FOS on allowable mean bearing pressure =

A FOS > 1 has been taken as adewate for mean

150 = 1.22123.17

bearing pressure(BD 30j87 c1.5.2.5.2). Mlowaile bearing pressure alreadyincludes a FOS which will be adeguate to cover againsteccentricity of loading.

Checking anticipated settlement; From Burland Broms andDeMello, Fig 21

A = 0.15 mm/kN/m2q

Assuming q = a~ then p = 0.15 x 173.63 = 26*O5 ~ totalsettlement.

Anticipated differential settlement 6 is likely to be 2/3 oftotal settlement, ie = 26.05 x 0.67 = 17.44 ~ across widthof foundation. For worst tilt, ~, assume settlement acrossshortest distance = width of abutment b’= 9.5 m;

A = 17.44 = 0.0018, or 1 in 5449.5 x 103

This is considered to be worst credible value of h and couldbe considered to be significant in the overall serviceabilityof the structure in terms of cracking.

5.3.2 Wall moments (SLS)

Unfactored in service realistic loads have been assumed whilstthe groundwater regime chosen represents long-term fullydeveloped profile. Earth pressure coefficients KO with Tfl= 1,in accordance with BD 30/87 cl.5.3.3 are used. It is alsoassumed that there are no eccentric vertical forces for theSLS condition. Lateral pressure on the stem is given bysimilar equations to those in Section 5.2.1, excepthlab= 13.55 - 0.28 = 13.27 m and hz,k= 0.28 m to modelgroundwater level with drainage in the backfill.

Lateral pressure at top of stem,P, = KO (WA~m~+ W~m) - 2 ctiKO

Lateral pressure at gwl on retained side,P* = pl + K. Tfmhla~- 2ctiK0.

Lateral pressure at base of stem,P3 = P2 + K. (~fti - ~w) h2sb - 2 C tiKO+ Tw h2,k

Hence force due to pressure above gwl,F1 = (pi + p2) hl,~/2= (28.71 + 127.88) X 13.27 / 2

= 1038.95 kN/m

This force has been assumed to act at h2,~+ 0.5hlti= 6.91 mabove base slab. This lever arm is known to be over-conservative.

And force due to pressure below gwl,F2 = (P2 + P~) h2ti/2= (127.88 + 124.42) X 0.28 / 2

= 35.32 kN/m

Similarly this force has been assumed to act at 0.5hztiabovebase slab = 0.14 m

Force due to soil in front of wall of depth z -t2 (= l.lm),

11

= 53.54 kN/m2

This force acts at about 0.37 m above base of stem.

Maximum moment, & at base of stem is given by the equation

= 7179.14 + 4.95 - 19.63

= 7164.46 kNm/m

Because of the limited information on steel reinforcementdetail, actual depths of concrete cover and spacing it is notpossible to check crack width criteria in accordance with BD44/90 Cl. 5.8.8.2. The maximum moment generated under SLSconditions (~ = 7164.46 kNm per m length of wall) is some75% of the ultimate moment of resistance, ~, of stem, (9530.78kNm/m, see section 5.2.1). Therefore there should not be aproblem with crack control. Indeed there is no visual sign ofdistress identified in the existing assessment report. Tileequations to be used, however, in the assessment of crackwidths are set out in BD 44/90 cl. 5.8.8.2 e~ation 24A arideqation 25.

12

Figure Cl ● Retaining wallm

‘ALIVE

‘1

h

Formation level(Allowing for 1m unplanned excavation)

--- ~G-WJ@t-SLa -v~- ,,,,::}:.::::::

‘2 I

INotes:

1. See legend for explanation of all symbols

2. h, and h * are heights with respect to ultimate limit state

assuming no drainage

3. h , :nd h 2sare heights appropriate to serviceability limit state

assuming full drainage

■

APPENDIX D. EXAMPLE ASSESSMENT: BRIDGE ABUTMENT

1 STRUCTURE DETAILS

Name Substructure No.1

Type Cantilever abutment on spreadfootings

Dimensions Shown in Figure Dl, attached

2 LOADINGS

Loads for foundations are unfactored in accordance with BS8004:1986 c1.2.3.2.4.1. Wind loading is ignored. BA 34/90“cl. 4.2 indicates also that factors of safety can be relaxedwhen assessing substructures and foundations. In addition BD21/93 cl. 5.10 indicates that assessment loading willgenerally be limited to dead plus superimposed dead andtype HA loading only. Notional lane and lane factors inaccordance with BD 21/93 cl. 5.6 and 5.7 are applied to theappropriate UDL and KEL values. The full HA loading inaccordance with BD 21/93 cl. 5.21 is applied. Reductionfactors given in BD 21/93 cl. 5.24 are not applied to the HAloading for the purposes of substructure and foundationassessment.

2.1 EmbanMent

- Dead Backfill assume granular imported fill

Tffl= 19 kN/m3 BD 21/93, Table 4/1

- Surcharge For abutment retaining horizontal backfillwSm=o

- Highway Assume Standard HA UDL and KEL for limitingcondition of loaded embankment length = 50mBD 21/93 cl. 5.21 and 5.22

UDL = 24.43 kN/m (limiting condition)per 3.65 lane width (see Fi~re 5/1 ofBD21/93).Road width = llm; from Table 5/3 of BD21/93.No. of notional lanes nbm is 4 of notionalwidth 2.75m. From Table 5.2 of BD 21/93 lanefactors for loaded length greater than 50m are1 over the 1st two lanes and 0.6 over the 3rdand 4th lanes therefore, total factored load is3.2

‘~L = 3.2 UDL n,.W4

= 78.19 kN/m

Wm = 120 kN per lane over two lanes plus0.6 x 120 kN over two lanes = 384 kN

From Table 5/2 of BD 21/93 the lane factor applied to the UDLand KEL values is 1 for limiting condition greater than 50m.Highway live loading on embankment is:

wALWE = wmLx W2 + w~

2.2 Structure

- Dead Self weight of bridgeWD= 7cm L w td/2

where ~- = 24 kN/m3w = 15.1 mL = 18.24 mtd = thickness =

Therefore the load on

Weight of abutment

= 610.75 kN

deck on one abutment

0.62m2/m width

each abutment WD= 2049.15 kN

WA~W= WI ~- [b’t2 + tlhm + tlhltil

where b’ = 6.2 m width of abutment base slabw, = 17.3 m length of abutment base slabW2 = 2.9 m width of heelt, = 0.9 m abutment stem thickness .t2 = 1.0 m base thicknessh = (8.63 - 3.65) m height above gwlh: = 3.65 m depth below gwl

wAB~ = 5799.1 kN

- Live ~ loading at abutment from bridge deck is given byBD 21/93 Fig. 5/1, consider only UDL contributionwith KEL acting on abutment vertical axis. FromTable 5/2 of BD 21/93 the lane factor applied to theUDL and KEL values is 0.75 for a bridge span, L =18.24m and notional lane width of 2.75m

wDL = 0.75 x 336 x (1/L)”.67kN/M= 36.18 kN per m length/lane

therefore the deck live loading is

3.2L W~@ba = 2111.75 kN4

From BD21/93 cI.5.30 allowance fOr fOOtways (WS = 2 mand Wd = 2.5 m) is 5 kN/m2

= L 5(w3 + W4) = 41O kN

Live load on each abutment (vertical)

WA = 2111.75 + 410 kN2

= 1260.87 kN

2.3 Smary of dead and live loads acting on on abutment

wDm =WD+WA= 3,310.02 kN

wABm = 5799.1 kN

3 EARTH PRESS~E COEFFICIE~S FOR THE BACKFILL (K., K.t KP)

“For imported granular material well compacted the Manual ofContract Documents for Highway Works Vol. 1 Specification forHighway works Series 600 Earthworks HMSO (1992) gives@’fd = 35°.

K. = I-sin@’fti= 0.27l+sin@’fti

&= l-sin@’ffl= 0.43

%= l+sind’~ = 3.69l-sin@’fW

Assume wall friction = O, and wall adhesion CW = O.

K= = 2(K,(1 + Cw/C’)) ‘A and ~ = 2(%(1 + cw/c’))’~

For backfilled abutments BD 30/87 cI.5.2 recommends that thefollowing coefficients are used;

SLS ULS

For structural elements KO 1.5& **

For soil elements K. K.

** It should be noted that B~5/94 c1.3.2 advises the use of1.5Ka for ULS. For cohesive backfills Km and KP are used tomodify earth pressures acting on the abutment.

4 ASSESSME~

The substructure is assessed for the following four limitstates namely ULS and SLS for both soil and substructure

Adoption of safe bearing capacities for foundation designshould avoid unacceptable settlements and tilting of thestructure.

5 ULTIMATE LIMIT STATE (ULS)

5.1 ULS of soil

This limit state corresponds to the following four failuremodes (BD30/87 cl.5.2.4.1)

sliding

failure of the foundation soil iebearing capacity failure

overturning

slip failure of the surrounding soil

The principles of analysis are based on CP 2 (1951) and BS8004:1986.

For ULS the following assumptions are made;

+ no drainage behind wall, ie high gwl

+ excavation in front of wall to lm below ground level,ie passive pressure neglected in top lm of ground

+ worst credible load combination is applied

5.1.1 Resistance to sliding (ULS)

Abutment foundation is checked for sliding using the equationfrom BS 8002:1994 cI.4.2.2.3. Bridge deck load has beenneglected in this mode for a worst case situation.

r = u’tan 6~= 0.75 o’tan @’

where T = base resistance~f = effective mean normal stresstan6~ = shear strength at the interface soilfoundation

The following load combinations need to be considered forworst condition:

(a) embankment dead load + abutment dead load.

Pressure on abutment base,

a, = M@ltiatiwmhlM7+ (~_ - ?wy+h2~ t,~l~

= (274.40 + 97.27 + 134.59 + 107.57)/ 6.2

4

= 99.01 kN/m2

Borehole BH 77 shows the founding soil to be a very dense finesand (Bagshot Sand) therefore

e’= 30+A+B

Since values for A and B were not available from the data c’of zero and @’of 34° based on Fig 14 Peck Hanson & Thornburn(1953) and c1.2.2.4, BS 8002 (2994) have been used.

thus 7, = 0.75 a’ tan 34

= 50.08 kN/m2

“Base area of abutment foundation = b’wl and depth of ground infront of wall, z, as shown on Fig Cl. Total resisting forceto sliding is therefore,

R= 7, b’wl +% W, Td Z2/2

= 5372.09 + 581.30 kN

= 5953.42 kN

Total sliding force F, is,

= 1104.48 + 465.76 + 1834.81

= 3405.05 kN

FOS to sliding = Resistance % = 5953.42 = 1.75Sliding F, 3405.05

CP 2 (1951) requires F.S 2 2 . The structure is thereforeinadequate against sliding.

(b) embankment surcharqe load + embankment dead load +abutment dead load + hiqhwav live loadinq

Resisting stress to sliding, 7b is the same as (a) plus anallowance for highway live load component on the base of thewall = WA~w~= 610.75 kN

7~ = 7a+ [w~~w~/(wlw2)]0.75 tan 34

= 56.24 kN/m2

5

Resisting force to sliding, & = base resistance pluspassive soil resistance in front of base

%= (T~ b’ + ~~ Td 22/2) WI

= 6032.13 + 606.45

= 6638.58 kN

Force causing sliding is equivalent to case (a) plushorizontal component of highway loading.

F~ = F, + K, (WWE/(WlW2)) (hlti+ hw + t2)w1+ K~ (W~/(WIWz))Z*Wl

= 3405.05 + 547.59

= 3952.60 kN

FOS to sliding = Resistance % = 6638.58 = 1.67Sliding F~ 3952.6

CP 2 (1951) reguires FOS 2 2 and therefore the structure isinadequate in sliding. Note that this example assessmentneglects the load contribution from the bridge deck whichwould increase the resistance to sliding. It is assumed thatfor ULS condition the abutment itself should be stable againstsliding.

5.1.2 Bearing pressure (ULS)

From borehole data BH 77 the founding strata is fine greysilty sand with SPT ‘N’ values ranging between 35 and 50therefore the worst credible value of N = 35 has been used.

From Peck Hansen & Thorburn (1953) @’P = 37°, NT = 60 andNq = 52, therefore Lambe and Whitman, pg 209

qWT = *W NT + 7fmdNq2

where d = depth of footing (1 m for worst credible condition)

= 19x6.2x60 + 19xlx522

= 4522 kN/mZ

Checking using Meyerhof; whereNq = 50 and NT = 55 (Tomlinson,

P. = 7ftihlds + (Tffl -7W) (h2ds

p. is mean effective stress,1975; Figure 2.21)

+ t2)

6

qWT = P. (Nq-l) + (titiw-2

= 8297.21 kN/m2

This confirmed that a WOrSt credible Value fOr q~T = 4522kN/m2 was appropriate.

Worst credible load on foundation from Section 5.1.1 is a,.

Mean bearing pressure, a~ = a, + (WA- + W~m) /b’wl

But from Section 2.3, WDm= WA+WD

Bearing pressure, u~ = 98.95 + f610.75 + 3310.0216.2x17.3

= 135.56’kN/m2

Thus the FOS against bearing capacity failure is

FOS = g~T = 4522 = 33.37a~ 135.56

CP 2 .(1951) reguires F.S 2 2 and the structure is thereforeadeguate under mean bearing pressure.

Check allowance for distribution of bearing pressure beneathfoundation

q- = Cb (l+6e/B)

where e = B/6 (i.e thrust falls on middle 1/3 rd)

= 2 X 135.56 = 271.12 kN/m2

Hence FOS = 4522 = 16.68271.12

CP 2 (1951) reguires F.S 2 2 and the structure is thereforeadeguate under the maximum local bearing presuure

5.2 ULS of structural element

the structure can fail by;

bending of the stem

shear of the stem

shear of the base

For the assessment of the stem it is assumed that the lateralpressure is based on no wall friction (CP 2.cl 1.435, 1951)

7

Earth pressures generated by the fill itself are factored asfollows:

Case 1, 1.5K0 used as recommended by BD 30/87 cl. 5.3.2

Case 2, 1.5 K, used as recommended by BA 55/94 cl. 3.2

These same factors are applied to the live loads as given byTable 1 of BD 37/88. This clearly is over-conservative andmight be relaxed in some assessment cases.

5.2.1 Wall moments (ULS)

For ULS the worst pressure distribution on the stem is due toembankment dead load + embankment surcharge + abutment deadload + deck dead and highway live load (assuming aneccentricity of 1 in 500).

Case 1, Usinu 1.5K0

Lateral pressure at top of stem,PI = 1.5 KO (W~w~/ W1W2)

Lateral pressure at gwl on retained side,P~ = P1 + 1.5 K. ~ftihl~a

Lateral pressure at base of stem,P3 = P2 + 1.5 KO (Tfti-TW) hm + ~. h2ti

Hence force due to pressureF, = (Pl + P2) hlti/2 =

= 191.07 kN/m

This force has been assumed

above gwl,(7.85 + 68.88) X 4.98 / 2

to act at hm + 0.5h1ti= 6.16mabove base slab. This lever arm is known to be over-conservative.

And force due to pressure below gwl,F2= (P2 + P3) hw /2 = (68.88 + 126.32) X 3.65 / 2

= 356.24 kN/m

Similarly this force has been assumed to act at 0.5hti = 1.83mabove base slab.

Case 2, Usinu 1.5K,Using similar equationsK~, the following forces

F1 = 119.97 kN/m

F2 = 248.01 kN/m

to case 1, except with KO replaced byare calculated:

Taking moments at base of stem; let E be the overturningmoment caused by the dead weight of the wall due to

8

eccentricity.eccentricity,of 1 in 500.

E =

For 8.68m height abutment thee, is 8.68/500 = 0.0174m assuming a tolerance

e x (WD~ + ‘AB~)/wl

= 0.0174 X (3310.02 + 5799.1)/17.3

= 9.16 kNm/m length of abutment

Maximum moment, & at base of stem is given by the equation

L = E + F1 X (h2ti+ 0.5h1ti)+ F2 x 0.5h2ti

Therefore for Case 1,L= 1838.07 kNm per m

and for Case 2L= 1202.03 kNm per m

For calculating the ultimate moment of resistance per metrerun of the stem, ~, available details of the reinforcement arelimited. It has been assumed that the compressionreinforcement is present and A, = ~’= 1% of concrete sectionarea. From BD 44/90 cl. 5.3.2.3, ~, is given by the formula;

w= (0.6fC”/T~)x(dNA~ - 0.5x) + f,’A,(d~A~ - d’m)

Assuming “fCu= 3.75 x 104 kN/m2, fy = 4.6 x 105 kN/m2,x = 0.5dNA~~,

f,’ = fy = 333 x 103 kN/m2

Tms + fy/2oooooo

Tm = 1.5 and ~~ = 1.15 are from Table 4a of BD 44/90 c14.3.3.3 and therefore,

M, = (0.6 X 3.75 X 104)0.42(0.83 - 0.21) + 333 x 103 x.0.01 X 1 X 0.83(0.83 - 0.05)

K = 6033.06 kNm/m

The stem therefore has FOS = 3.32, for Case 1Case 2, and thus satisfies ULS in bending for

5.2.2 Shear stress in stem (ULS)

and 5.02 forboth cases.

From BD 44/90 cl. 5.7.3.2 and cI.5.4.4.Z the shear stress permetre run, v, at any cross section is given by the equation;

v= V/(dNA_)

where shea’rforce, V.= F1 + F2.

The criteria given in BD 44/90 cl. 5.3.3.2 is that v shouldnot exceed the ultimate shear stress of the concrete,

VW = (0.24/~mv)(100A,/dNAsm)’’3(fm)‘n

where Tmv = 1.25, V* = 642.65 kN/m2

For the stem there are two cases to check because of the useof either KO or K,:

For Case 1: 1.5 x K.

v= (191.07 + 356.24)/0.83 = 659.41 kN/m2/m

.For Case 2: 1.5 x K,

v= (119.97 + 248.01)/0.83 = 443.35 kN/m2 /m

The stem is therefore inadequate for shear (ULS) for Case 1(FOS = 0.97) as v S v“h. Case 2 (FOS = 1.45) is satisfactory.It was not possible to check accurately for adequate shearreinforcement because of the lack of information onreinforcement detail. It must be noted that a factor of 1.5has been used throughout on dead and live loads with respectto earth pressure; unfactored live loads would probably havebeen used in agreement with the assessment authority.

5.2.3 Base and punching shear (ULS)

In addition to the above, it is also necessary to check theshear stress on the abutment base in accordance with BD 44/90c1.5.7.3.2. The shear strength of the base is governed by themore severe of:

shear along vertical section at a distance equal to theeffective depth from the face of the loaded area,BD 44/90 c1.5.4.4.1

punching shear around the loaded area, BD 44/90 cl.5.4.4.2 applies, for a critical section on a perimeter1.5d from the boundary.

For base shear a uniform pressure distribution beneath basehas been assumed.

‘b= = ~b WI (b’-(w2+0.5t1)) - w, t, (~~~c hluls+ (~CONC ‘?W)h2ti)

- WD=

VPC~= W~H + W, t, (T~Nc hlti+ (7~NC ‘~w)h2ti)

v= v- /wldN*~~~or V_/ wl (2 x 1“5 ‘NABASE + ‘1)

= 46.40 kN/m2 or 98.02 kN/m2

10

In both cases the ultimate shearrecalculated as 642.65 kN/m2 fornrocedure in section 5.2.2. For

strength, V* has beenthe base following thebase shear, FOS = 13.77 and

~or base punching shear FOS = 6.56.

5.3 SERVIC~ILITY LIMIT STATE (SLS)

For SLS assume;

+ full drainage and developed groundwater profile

+ worst credible load combination in service

5.3.1 Allowable bearing pressure (SLS)

Foundation is fine grey silty sand with SPT ‘N’ value = 35,worst credible value.

From BS: 8004 Table 1 a minimum presumed bearing value of 300kN/m2 is appropriate. For 6m wide footing an allowable bearingcapacity of 310 kN/m2 is derived (Terzaghi and Peck, 1967).From Tomlinson (1975) Table 2.1 a presumed bearing value ofbetween 250 to 400 kN/m2 is shown for a 4m wide footing andsettlement not to exceed 50mm. Thus qdw = 300 kN/m2 has beenused as the allowable bearing capacity.

FOS on allowable bearing pressure = 300 = 2.24135.56

CP 2 (1951) reguires F.S 2 2 the structure is thereforeadeguate

Check anticipated settlement. From Burland Broms and DeMello,Fig 21

& x 0.06 mm/kN/m2q

Assume q = a~ hence p = 0.06 x 135.56 = 8.13 m totalsettlement.

The anticipated differential settlement 6 is likely to be 2/3of the total settlement ie

P = 8.13 X 0.67 = 5.45 mm across width

For worst tilt, ~, assume settlement across= width of abutment b’= 6.2m;

A = 5.45 = 0.0009, or 1 in 11386.2 X 103

This is considered to be the worst credible

of foundation.

shortest distance

value of X and isnot considered to be significant in the overall serviceabilityof the structure Note: 6 allowable for this structure is 10mmas stated in existing -sessment.

11

5.3.2 Wall moments (SLS)

Unfactored in service realistic loads have been assumed whilstthe groundwater regime represents the long-term fullydeveloped profile. Earth pressure coefficients & with ~fl= 1,in accordance with BD 30/87 cl.5.3.3 are used. It is alsoassumed that there are no eccentric vertical forces for theSLS condition. Lateral pressure on the stem is given bysimilar equations in Section 5.2.1, except, hl,b= 8.63 - 1.32 m= 7.31m and h2,k= 1.32 m to model groundwater level withdrainage in backfill.

Lateral pressure at top of stem,P, = KO (WA~~~/WIWZ)

“Lateral pressure at ~1 on retained side,P~ = PI + K. ~fwhlti

Lateral pressure at base of stem,P3 = P2 + Ko (~ffl-TW) h2,k+ TW h2,~

Hence force due to pressure above gwl,F, = (Pl + P2) h,,b/2 = (5.23 + 64.95) X 7.31 / 2

= 256.55 kN/m

This force has been assumed to act at h2,b+ 0.5h1,h= 4.98mabove base slab. This lever arm is known to be over-conservative.

And force due to pressure below gwl,F2= (P2 + P3) h2,k/2 = (64.95 + 83.13) X 1.32 / 2

= 97.73 kN/m

Similarly this force has been assumed to act at 0.5h2,b= 0.66mabove base slab.

Maximum moment, & at base of stem is given by the equation

L= F, X (hak + 0.5hl,b)+ F2 X 0.5h2ti

= 1277.62 + 64.50 = 1342.12 kNm/m

Because of the lack of information available on steelreinforcement detail, actual depths of concrete cover and barspacing it is not possible to check crack width criteria inaccordance with BD 44/90 cl. 5.8.8.2. The maximum momentgenerated under SLS conditions (~ = 1342.12 kNm/m length ofwall) is some 22% of the ultimate moment of resistance, ~, ofstem, (6033.06 kNm per m length of wall see Section 6.0).Therefore there should not be a problem with crack control.Indeed there is no visual sign of distress identified in theexisting assessment report. The equations to be used,

however, in the assessment of crack widths are set out in BD44/90 cl. 5.8.8.2 epation 24A and e~ation 25.

12

‘Is

Figure DI: Cantilever abutment#

. .

Backfil

‘1

I

Weep hole

Notes:

I 1. See legend for explanation of all symbols

I 2. h, and h 2 are heights with respect to ultimate limit state

assuming no drainage

3. h , ~nd h 2sare heights

assuming full drainage

appropriate to serviceability limit state

~ w- FmGs I

~NT / STRUCTURE DIMNSIONS DECK DIMENSIONS WTERIN LOADING DATA DECK LOADING EARTH PRESSURE MATERIAL STRENGTH PROPERTIES STRUCTUWL PROPERTIES

PROPERTIESSOIL PROPERTIES

1

No Nwlw2tl lltt2hlh2hlh2 ha ZZskwONABUTMENT BACKFILL

Ltdn w LWF~ULSSLS=

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li

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16

a76W20~W6 “0271 96W

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to 666 17.66 SS6 f.Q !.42 1.22 7,Q f.07 7.32 1.07 a3S O 2.~ O.W t7,6t t6S6 0s7 4 $64 007W

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~m Pm

~NT / STRUC~E DIMENSIONS DECK DIMENSIONS MATERIAL LOADING DATA DECK LOADING EARTH PRESSURE MATERIAL STRENGTH PROPERTIES .’ STRUCTURAL PROPERTIESPROPERTIES

SOIL PROPERTIES

No bwlw2tltltt2hlh2hl h2h azzskw Ltdn w LWON ABUTMENT WKFILL

YY7 WSUR w tiEL w~uT WALIVEULS US SS S1S

WD WA c’ + Ka KO Kp fcu y FY y FS dNAu ETLdNA, dsn Q Qlan~tlm* Com fin Sdl am

do O C’ Ka KP

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~m a- .

~NT / STRUC= Dl~NSIONS OECK OIMkNSIONS WTERIA LOAOING OATA DECK LOADING EARTH PRESSURE MATERIAL STRENGTH PROPERTIES STRUCTURAL PROPERTIES SOIL PROPERTIES

PROPERTIES

No Mwlw2tl tltt2hlh2hlh2 huZZskw Ltdn w LW

ON ABUTMENT BACKFILL

ULBWSLSSLS ,777 WSUR ~ WEL W%UT WALIVE WO WA c’ ~ Ka KO KP fcu 7 FY y FS dMd ASTLdNAd ASTLQ Q

tmc Imo CON M COBdO o c’ Ka Kp

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00

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~HQ WMLS

~MNT / STRUCTURE DIWNSIONS OECK DIMENSIONS ~TERW LOAOING DATA DECK LOAOING EARTH PRESSURE WTERIAL STRENGTH PROPERTIES

PROPERTIES

STRUCTURAL PROPERTIES SOIL PROPERTIES

No Vwlw2tltllt2hlh2hl h2ha ZZskw Lldn w LWF

ON ABUTMENT ~CKFILL

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ASSESSMENT OF SUBSTRUCTURES (BD24/92) WORKSHEET 1 INPUT DATA FILE

DIMENSIONS, MATERIAL AND SOIL PROPERTIES AND LOADS

——.——- —-. .— —-— —.— ——— — . .-.—., - ,“.—

AE~E~ SP- FOO~OS I

SL~NG OF FOUNDATIONULTIMATE LNn STATE STRUCTH ELEMENT

LO~ CASE ABEARWG PRESSURE BENDNG N THE STEM BENDNG N THE STEM: ~ STRESS W STEM SHEAR ST~SS N BASE

LOAOCASEB Ko PRESSURE KS ESSUREBSE ~S SLD BsE REs SLD MN FDN Mu f! F2 MC MMW FOS FI F2 Mum FOS WKO FOSKO KM FOSti

LOA73 RSE 5L0UT -E

FCEFOS MCH FOS

FOS RSE SLO FCE FOS ms FOS ULs ULs us l,5m ULs ULs ULS I,sti SASS NH

1 69 50 5953 340s 1.15 56 6580 3928 1,68 237 19.09 6068 107 4f4 o 1916 3.17 139 309 f427 4.27 723 724 1.00 S40 1.34 40 47.9? 120 e 02

4 118 47 3824 2119 1.91 53 4*99 2707 1.55 367 2.04 5197 293 50 0 1065 4.60 220 33 801 649 671 420 l.m 310 2.17 -469 %.43 23S 2.05

5 125 63 5920 2003 296 71 8511 2512 2.59 33s 2.04 4263 338 265 0 2205 *,95 242 188 1575 2.73 671 794 085 562 1.19 -168 4,03 104 3.65

7 92 69 10602 153s 669 85 11395 216s 5.26 218 926 f366 309 0 0 945 1.47 221 0 675 2.05 300 358 084 256 1.17 -63 5.93 105 3,21

8 130 56 5880. 3118 1.02 63 8251 3792 1.85 296 304 9736 452 0 0 2063 4.67 206 0 1415 em 275 318 0.87 215 1.28 -44 26.23 133 2.10

11 110 56 4537 2699 1.66 65 5140 34B9 1.47 267 336 1851 416 70 0 1741 0.95 304 47 1271 1.30 650 S64 0 ?4 638 1.02 -14 253.57 100 5,34

12 122 64 12912 4731 2.56 7~ 13178 5617 2.34 320 2.74 94W 420 0 0 1669 5.59 296 0 1205 7.64 315 326 0.93 241 1.31 -323 2.96 217 2.02’

16 140 71 18472 5972 309 76 19641 6659 2.66 315 1.90 7906 26S o 0 1464 5.39 277 0 1045 7.56 417 341 ;.22 243 1.72 -66 16.46 92 5.07

19 146 74 11345 2983 3.60 61 12196 3622 337 339 1.77 1494! 391 ~19 o 1921 7,77 277 79 1365 10.94 433 356 1,22 250 1,74 -95 11.27 114 4.23

AEWE~ PUD

SL~NG OF FOUNDATWULTWTE LN~ STATE ST~TH ELEMENT

LO~ CASEABEARNG PRESSURE BENDWG M THE STEM: BENDNG N THE STEM: SHEAR STRESS N STEM

LOADCASEB h PRESSURE KS PRESSURES= STRESS M BASE

BSE RES SLO ess REs SLO Mm FDN MU FI F2 Ms MMU FOS F1 F2 MMM FOS. UT WKO FOSKO vti FOSK8 -E

LOAO RSS SLD FcE FOS RSE SLO FCE FOS Rss FOS us MS

FOS WNCH FOS

Us 1,5K0 us ULs ULS 1.5W BASE mCH

14 118 43 8211 2776 2.96 47 6677 3331 287 265 1.56 1013 263 0 0 895 133 205 0 649 1,56 4~ 7 567 .0.74 410 1.02 -60 24.31 04 5.51

15 92 34 7309 2166 337 26 6006 26S6 2.96 226 1.99 2466 193 0 0 496 4.99 143 0 370 6.72 437 285 <.58 196 213 -30 m63 al S.76

17 122 43 11012 5783 1.90 43 11792 6654 ~.77 275 055 2547 364 0 0 1329 1.92 261 0 952 2.6B 623 506 1.23 363 1.72 46 ~4.34 76 9.28

20 149 75 9677 2756 356 63 10672 3406 3.13 349 1.29 15202 396 59 0 1720 666 261 42 1222 12.44 304 316 0.96 222 1.37 -111 6.46 100 3.14

~WE~ SLOPING

SLIDING OF FOUNDATIONULTIMATE LIMn STATE STRUCTURAL ELEMENT

BEARING PRESSURELOAO CASE A

BENDING N THE STEM:LO~ CASEB

BENDNG W THE STEM: SHEAR STRESS IN STEMKo PREssum Ke PRESSURE

SHEAR STRESS M BASE

BSE RES SLO BSE RES SLO ti~ FON Mu FI F2 MS MMti FOS, F1 F2 MMm FOS WLT v KO FOS. m WKO FOS:W -SE

LOAD RSE SLO FCE

FoS ~NCH FOS

FOS RSE SLO FCE FOS ms FOS ULs ULs ULs 1.5K0 uLS ULS ULS 1.5K0 BASE ~CH

2? 116 51 3240 7124 266 60 3681 1563 2.32 300 3.33 11210 246 76 525 9445 7.75 179 51 1190 942 229 244 094 173 1.33 -144 6.10 98 2.72

22 136 60 10519 2508 4.19 69 11319 3263 347 303 4.96 e666B 320 263 901 2930 22.74 228 *84 2349 2037 209 240 0.67 170 1.23 -60 14.74 101 359

23 136 60 10763 3175 339 70 11667 4076 2,66 37 4.38 66666 347 369 1039 3709 17,97 246 263 2941 22.67 206 295 0 7+ 209 1.00 -37 6676 106 3.42

24 110 46 6432 2620 2.45 56 7403 3369 211 250 6.00 7152 377 153 018 275o 2.60 267 103 2167 3.27 372 469 0.79 228 1.13 41 15.32 63 349

25 117 51 6669 2427 275 57 73s0 2697 2.45 273 366 7414 319 199 744 2546 2.91 229 136 2035 3.64 466 459 1.02 324 1.44 40 14.12 110 4,52

~-NO WALLS

SL~NG OF FOUNDAT~ULTMTE LN~ STATE STRUCT~ ELEMENT

BEARNG PRESSURE BENDWG N THE STEM: BENDNG N THE STEM: SHEAR STRESS N STEM SHEAR ST=SS N BASELOAD CASE A LO~ CASE B

BSE -SKc4PRESSURE KS PRESSURE

SLD BSE RES SLO MU FDN Mu FI F2 M6 ~MM FoS FI F2 MMM FOS tiT wKO wLOAO RSE SLO FCE FOS RSE SLD

FoSti WW FOSKA FOS ~H FOSFCE FOS %s FOS ULs . ULs ULs 15K0 ULs ULs ULS 1.5Ka w Wh

2 121 52 565 529 1.07 56 596 582 1,02 262 360 3646 131 1319 0 7063 0.52 93 1063 5551 0.66 676 2$65 0.31 1725 0.39 361 1,76 54 f2.46

3 112 46 1071 521 2.05 53 1113 630 1.77 235 1.92 10246 667 649 0 B295 1.24 333 616 4620 2.22 643 1331 0,46 632 0.77 507 1.06 68 7.68

6 54 27 353 166 213 33 376 220 j.72 116 37.20 2077 165 296 0 1176 1.76 75 216 652 3.16 466 657 0.74 412 1.18 315 1,6s 31 17.20

9 160 69 365 336 1:14 72 396 394 1.01 340 2.65 4064 793 44 0 3165 1.29 ~7 27 630 4,92 759 1333 0,57 372 2.04 519 1.09 43 12.90

10 46 23 77 54 1.40 28 66 107 0.63 113 354 563 147 35 0 317 1.64 85 23 165 315 566 652 0.06 269 145 316 1.s6 26 21.44

13 90 39 133 71 1.67 43 144 119 1,22 207 2.18 1176 214 0 0 461 2.55 124 0 266 4.41 566 496 1,13 267 1.97 06 6.94 2E 20.67

16 112 47 264 97 2.92 52 309 ~57 1.96 246 0,41 3162 209 114 0 1435 2.22 214 76 1051 303 396 426 0.93 305 130 59 7,93 63 7.57

ASSESSMENT OF SUBSTRUCTURES (BD24/92) WORKSHEET 2 CALCULATIONS ULTIMATE LIMIT STATE

I

A5~ENT6 5P- FOO~NGS

SE~CEABILITY LIMIT STATE OF SOIL SE~CEABILl TY LIMIT STATE STRUCTURAL ELEMENT

SETTLEMENT OF THE FOUNDATION BENDING IN THE STEM: KO MOMENT RESISTNCE

Q F1 F2 F3 MMM

ALLOW FOS @ P x SLS SLS SLS SLS FOS

1 300 2.53 0.0600 7.11 7,64E-04 252 405 0 1325 4.59

4 450 2.45 0.0600 11.01 0.001721 218 0 0 720 7.2~

5 230 1.36 0.0800 13.56 0.00145 267 107 0 1536 279

7 1000 9.28 0.0153 1,64 0.000359 206 0 286 430 3.22

8 300 2.03 0.1000 f14,70 0.00179 285 0 0 1303 7.47

11 300 2.25 0.0660 8.60 0,00148 277 47 0 1157 1.43

12 300 1,s8 0.0600 959 0,00126 200 0 0 1119 6,44

16 200 1.27 0.0600 9.46 0.00105 256 0 0 97~ 6.14

19 300 ~.77 0.0600 13.54 0.00132 260 63 23 1266 11.78

A5-E~ PILSD

SETTLEMENT OF THE FOUNDATION BENDING IN THE STEM: KO MOMENT RESISTNCE

Q FI F2 F3 MMM

ALLOW FOS m P A SLS SLS SLS SLS FOS

*4 150 1.05 0.1000 14.27 0,00147 169 0 0 593 ~.74

15 150 1.33 0.1000 11.32 0.00123 429 0 0 329 7,55

17 50 0.36 0.6000 62.42 0.009$6 243 0 0 002 2.89

20 150 0.66 O.iooo +7,47 0.00?91 264 44 9 1136 13.36

A5~ENTS 5LOPIN0

SETTLEMENT OF THE FOUNDATION BENDING IN THE STEM: m MOMENT RESISTWCE

Q 1 FI F2 F3 MMM

ALLOW FOS @ P L SLS SLS SLS SLS FOS

21 400 2.67 0.0500 7.50 0.00111 165 53 2 1134 9.66

22 500 3.30 0.0600 9.08 0.000903 . 325 44 t 30 2306 28.91

23 430 290 0.0600 11.86 0.00113 369 79 106 2908 2292

24 500 4.00 0.0600 10.00 0.00117 316 31 11 2194 3.26

25 300 2.20 0.0500 6.83 0.000642 269 69 6 2012 3.66

~~NINO WALLS :

SETTLEMENT OF THE FOUNDATION BENDING IN THE STEM: KO MOMENT RESISTNCE

Q FI F2 F3 MM~

ALLOW F OS Wo P k SLS SLS SLS SLS FOS

2 300 2.26 0,0600 10.51 0.00092 519 t74 63 3947 0.92

3 150 1.28 01500 17.61 0.001242 909 32 26 6262 1.63

6 1000 17.20 00229 1,33 0,000194 28? 179 27 781 2.66

9 300 1.77 0.0800 13,59 0.00206 463 63 0 2005 2.04

10 125 2.2t 02000 11,29 0.00301 96 24 0 211 2.76

13 150 1,45 0,0600 6.2o 0.00138 143 0 0 307 363

16 50 041 0.6000 73,9* 0.00987 160 76 0 892 3.57

ASSESSMENT OF SUBSTRUCTURES (BD24!92)

WORKSHE= 3 CALCULATIONS

SERVICEABILITY LIMIT STATE