Integral Bridges

PUBLICATION NUMBER P163

Integral Steel Bridges:

Design Guidance

A R BIDDLE BSc, CEng, MICE

D C ILES MSc, ACGI, DIC, CEng, MICE

E YANDZIO BSc, MEng, CEng, MIMarE

Published by:

The Steel Construction InstituteSilwood ParkAscotBerkshire SL5 7QN

Telephone: 01344 623345Fax: 01344 622944

P163: Integral Steel Bridges: Design Guidance

Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

iiP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003

1997 The Steel Construction Institute

Apart from any fair dealing for the purposes of research or private study or criticism or review, aspermitted under the Copyright Designs and Patents Act, 1988, this publication may not bereproduced, stored, or transmitted, in any form or by any means, without the prior permission inwriting of the publishers, or in the case of reprographic reproduction only in accordance with theterms of the licences issued by the UK Copyright Licensing Agency, or in accordance with the termsof licences issued by the appropriate Reproduction Rights Organisation outside the UK.

Enquiries concerning reproduction outside the terms stated here should be sent toThe Steel Construction Institute, at the address given on the title page.

Although care has been taken to ensure, to the best of our knowledge, that all data and informationcontained herein are accurate to the extent that they relate to either matters of fact or acceptedpractice or matters of opinion at the time of publication, The Steel Construction Institute, the authorsand the reviewers assume no responsibility for any errors in or misinterpretations of such data and/orinformation or any loss or damage arising from or related to their use.

Publication Number: P163

ISBN 1 85942 053 2

British Library Cataloguing-in-Publication Data.A catalogue record for this book is available from the British Library.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

iiiP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003

FOREWORD

Integral bridge construction eliminates the provision of movement joints betweensuperstructure and substructure and thus avoids details that have given rise to manydurability problems in the past.

A number of studies have been carried out by The Steel Construction Institute on thebehaviour of integral bridge structures and this has led to the conclusion that the use of steelelements in the bridge substructure (sheet piling, High Modulus Piles and steel bearing piles)offers alternative construction sequences and methods which may well be cheaper and morefit-for-purpose than the traditional reinforced concrete form of construction.

The purpose of this publication is to provide advice and guidance in the design of integralbridges that use steel in a composite deck, in the substructure, and in both. It is alsointended to promote innovative thought by designers on alternative means of providingbridge supports in integral bridges to those used traditionally in non-integral bridges. Inpresenting new forms of substructure, the guide draws on technology that has beendeveloped over the past three decades in the Offshore oil and gas construction industry.

Use of steel in the substructure to bridges saves in dead load, provides material ductility andpermits speedier construction, all of which are significant advantages on many bridgeschemes. The use of prefabricated steel deck beams and steel piling saves site occupancytime and minimises the traffic interruption for replacement bridge projects. It is hoped thatthis Guide will encourage designers and constructors to consider a steel substructure optionmore frequently during the conceptual and preliminary design phases of projects and therebyto take advantage of the available potential to build more efficiently.

During the preparation of the publication, comment was received from the following people,and their advice is gratefully acknowledged:

Mr S G Griffiths Buckinghamshire County CouncilMr B Simpson Ove Arup & PartnersMr J L Vincett Tony Gee & PartnersMr R E Craig WS Atkins

Funding for the initial studies and for part of the cost of preparing the text of this publicationwas provided by British Steel, Sections, Plates & Commercial Steels and by British SteelTubes & Pipes. The assistance of Mr W Ramsay, Mr J Wilson and Mr E F Hole of BritishSteel is also gratefully acknowledged.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

ivP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

vP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003

CONTENTSPage No.

SUMMARY viii

1 INTRODUCTION 1

2 WHAT IS AN INTEGRAL BRIDGE? 22.1 Definition and terminology 22.2 Frame abutment integral bridges 22.3 Pinned integral bridges 32.4 Bankseat integral bridges 42.5 Jointless deck bridges 52.6 Additional considerations when choosing integral construction 6

3 WHY CHOOSE AN INTEGRAL BRIDGE? 93.1 Experience with non-integral construction 93.2 Highways Agency requirements 103.3 Advantages of integral bridges 103.4 Practical aspects of the site that influence choice 113.5 Whole life costing 123.6 The use of steel piles in integral bridges 12

4 HISTORICAL BACKGROUND 154.1 Integral bridges in Europe and the USA 154.2 Examples of integral bridges in the United Kingdom 174.3 Offshore experience with tubular hollow sections 19

5 SUBSTRUCTURES FOR INTEGRAL BRIDGES 215.1 Frame abutment integral bridges 215.2 Bankseat integral bridges 255.3 Pinned integral bridges 265.4 Jointless deck configuration 285.5 Intermediate supports 295.6 Bearings 315.7 Skew bridges 33

6 STEEL SECTIONS FOR INTEGRAL BRIDGE PIERS AND ABUTMENTS 356.1 Continuous wall steel pile sections 356.2 Box piles 376.3 Tubular piles 386.4 H-Piles 396.5 Installation tolerances 40


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

viP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003

6.6 Environmental factors associated with driven piles 416.7 Driveability 416.8 Corrosion allowances 42

7 DESIGN BASIS 467.1 General principles 467.2 Design standards 467.3 Limit state design 507.4 Loading effects on foundations 517.5 Observational Method for foundation design 517.6 Design report 527.7 Design for fatigue 53

8 DESIGN METHODOLOGY 548.1 Design sequence 548.2 Preliminary stages 568.3 Design of embedded retaining wall abutments 578.4 Design of column-pile abutments and piers 638.5 Design of bankseat integral bridges 658.6 Deck design 66

9 SITE INVESTIGATION AND SOIL DATA FOR DESIGN 679.1 Soil data required for design 679.2 Site investigation 679.3 Selection and evaluation of soil parameters 689.4 Soil parameters for design of integral bridges 68

10 ABUTMENT WALLS - EMBEDDED WALL STABILITY 7010.1 Cantilever and propped walls 7010.2 Methods of analysis for stability against overturning 71

11 ABUTMENT WALLS - SOIL-STRUCTURE INTERACTION 7611.1 Soil-structure interaction approach 7611.2 Mobilisation of earth pressure and soil-structure interaction 7611.3 Soil-structure interaction analysis methods 7711.4 Global analysis of integral bridges 7911.5 Available soil-structure interaction analysis software 7911.6 Boundary conditions at the deck to abutment connection 81

12 ABUTMENT WALLS - RESPONSE TO THERMAL DECK MOVEMENTS 8412.1 Bridge temperatures 8412.2 Soil behaviour under cyclic loading 8512.3 Earth pressures due to wall displacement 86


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

viiP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003

12.4 Requirements of BA 42/96 8812.5 Comparison of Kp values in BA 42/96 with BS 8002 90

13 STEEL PILES - AXIAL LOAD RESISTANCE 9313.1 Ultimate axial capacity and load transfer 9313.2 Vertical settlement and serviceability 9413.3 Ultimate capacity in cohesive soils 9513.4 Ultimate capacity in cohesionless soils 9613.5 Ultimate capacity in rock 9613.6 Mobilisation of wall friction on a retaining wall 9713.7 Determination of friction surface area 9813.8 Determination of end bearing area 9913.9 Buckling aspects of fully and partially embedded piles 99

14 STEEL COLUMN-PILES - LATERAL LOAD RESISTANCE 10114.1 Lateral loads from soil 10114.2 Lateral forces at pile head 10114.3 Analysis of pile groups 10314.4 Behaviour of a spill-through column-pile abutment 10714.5 Integral bridges and crash resistance 109

15 COMPOSITE DECK DESIGN 11015.1 Axial Loading 11015.2 Moments due to frame action 111

16 REFERENCES 112


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

viiiP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003

SUMMARY

Integral bridge construction is now being actively pursued as a means to avoiddurability problems associated with the movement joints used in traditionalbeam-type bridges.

This publication explains what is meant by an integral bridge and illustrates thevarious structural configurations that may be used. A key aspect of theperformance of an integral bridge is that the bridge supports, and the soil that theyretain, are displaced by the cyclic thermal strains experienced by the bridge deck.Bridge designers will need to learn how to deal with the response of the soil andsupport structures to such displacements and to develop expertise in this newconcept.

Guidance is provided on the design basis for integral bridges and the designmethodology that will need to be followed, both for bridges with retaining wallabutments and for bridges on bankseats or individual pile supports.

The use of steel piling in the bridge supports offers a compliant structural elementthat is well suited to integral bridge construction. The behaviour of the steelsupports under the loads from the deck and pressure from the soil is explained.

The requirements of the Highways Agency are discussed and compared with otherstandards and design rules relating to soil behaviour. The interaction between thestiffnesses of the deck, the supports and the soil is explored and the requirementsfor the connection between the two are examined.

Reference is made to the companion publications Steel integral bridges: Design ofa single-span bridge - Worked example and Steel integral bridges: Design of amulti-span bridge - Worked example, which illustrate many of the aspects coveredin this publication.

Pont en acier de type intgral: guide de dimensionnement

Rsum

La construction de ponts de type intgral est actuellement en plein essor car ellepermet dviter les problmes de durabilit lis aux appuis mobiles des ponts poutres traditionnels.

La publication explique le concept de pont intgral et illustre les diffrentesconfigurations structurales qui peuvent tre utilises. Un point trs important quiconditionne le bon comportement de ce type douvrage est celui des dplacementsprovoqus, dans les appuis et le sol quils retiennent, par les mouvements dutablier du pont dus aux variations thermiques. Il est indispensable que lingnieurprojeteur soit bien au courant de ce problme et puisse le prendre en compte demanre correcte.

Le guide couvre les points principaux du dimensionnement des ponts de typeintgral et expose la mthodologie suivre tant pour le dimensionnement du pont,pour les murs supports situs aux extrmits du pont et pour les piles de ponts.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

ixP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003

Lutilisation de piles en acier comme appuis du pont convient particulirement bienpour ce type de constructions. Le comportement de ces supports en acier estexpliqu tant sous les charges provenant du tablier du pont que sous la pousse desterres.

Les exxigences des autorits responsables des routes sont discutes et compares dautres codes et rgles de dimensionnement relatifs au comportement des sols.Linteraction entre les rigidits du tablier, des appuis et du sol est analyse et desrecommendations sont formules pour atteindre un bon comportement densemble.

Le guide fait rfrence deux publications consacres au mme sujet et intitulesPonts en acier de type intgral: dimensionnement dun pont simple porte -exemple dapplication et Ponts en acier de type intgral: dimensionnement dunpont portes multiples - exemple dapplication qui illustrent de nombreuxaspects couverts dans cette publication.

Rahmenbrcken aus Stahl: Anleitung zur Berechnung

Zusammenfassung

Der Bau von Rahmenbrcken wird aktiv verfolgt als ein Mittel, Probleme derDauerhaftigkeit zu vermeiden, die sich bei gewhnlichen Balkenbrcken infolge vonbeweglichen Auflagern ergeben.

Diese Verffentlichung erklrt den Begriff Rahmenbrcke und zeigt dieverschiedenen statischen Systeme. Ein entscheidender Gesichtspunkt des Verhaltenseiner Rahmenbrkke ist die Verformung im Bereich der Auflager und des gesttztenBodens infolge zyklischer, thermischer Dehnungen des Brckenbalkens.Brckenplaner mssen lernen, mit der Antwort des Bodens und der Auflager auf dieVerformungen umzugehen und Erfahrung mit diesem neuen Konzept zu sammeln.

Grundlagen zur Berechnung von Rahmenbrcken und die anzuwendendeBerechnungsmethodik werden vermittelt, sowohl fr Brcken mit Widerlagerwndenals auch fr Brcken mit Auflagerbnken oder Auflagem aus Pfhlen.

Stahlpfhle fr die Brckenauflager sind ein gnstiges bauliches Element, das gutzum Bau von Rahmenbrcken pat. Ihr Verhalten unter der Belastung aus demBrckenbalken und dem Erddruck wird erklrt.

Die Anforderungen der Straenbaubehrde werden besprochen und mit anderenVorschriften und Berechnungsregeln hinsichtlich des Bodenverhaltens verglichen.Die Interaktion zwischen der Steifigkeit des Brckenbalkens, der Auflager und desBodens sowie die Anforderungen fr die Verbindung zwischen den beiden, werdenuntersucht.

Auf die begleitenden Publikationen Rahmenbrcken aus Stahl: Berechnung einereinfeldrigen Brcke - Berechnungsbeispiel und Rahmenbrcken aus Stahl:Berechnung einer mehrfeldrigen Brcke - Berechnungsbeispiel wird Bezuggenommen; sie illustrieren viele der Aspekte, die in dieser Verffentlichungbehandelt werden.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

xP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003

Ponte integrali in acciaio: guida progettuale

Sommario

Il notevole interesse recentemente manifestato per il sistema costruttivo dei pontiintegrali risulta motivato dalla possibilit di evitare, con riferimento ai tradizionalisistemi di ponte a travata, i problemi di durabilit imputabili agli spostamenti deigiunti.

Questa pubblicazione introduce il significato di ponte integrale e presenta levarie tipologie strutturali che possono essere utilizzate. Un aspetto peculiare delcomportamento di ponti integrali rappresentato dal fatto che gli appoggi daponte, unitamente al suolo che li sostiene, non sono soggetti agli effetti provocatidalle escursioni termiche dellimpalcato del ponte. I progettisti di ponti dovrannodi conseguenza essere in grado di trattare la risposta del terreno e degli appoggidella struttura in relazione a tali spostamenti, sviluppando quindi esperienza inquesto nuovo settore.

Viene presentata una guida per la progettazione di base di ponti integrali, conriferimento alla metodologia di calcolo da utilizzare, sia per ponti con spalle aparete sia quelli che poggiano su argini o su singole pile.

Luso di pile in acciaio per lappoggio della travata rappresenta una soluzioneestremamente conveniente, bene integrabile con il sistema costruttivo in esame. Eanalizzato il comportamento degli appoggi da ponte in presenza dei carichitrasmessi dallimpalcato e delle azioni esercitate dal terreno.

I requisiti di queste strutture imposti dagli enti preposti alla viabilit sono discussie paragonati con altri criteri generali e con regole di dimensionamento legate alcomportamento del terreno. Linterazione tra la rigidezza di impalcato, appoggie terreno analizzata e sono esaminati i requisiti dei collegamenti.

Viene fatto riferimento alle pubblicazione sulla stessa tematica Ponti integrali inacciaio: progettazione di un sistema a campata singola - esempio applicativo ePonti integrali in acciaio: progettazione di un sistema a pi campate - esempioapplicativo, le quali trattano molti degli aspetti affrontati in questa guidaprogettuale.

Puentes de acero integrales: Gua de Proyecto

Resumen

Actualmente la construccin de puentes integrales se ve favorecida con un intentode evitar los problemas de durabilidad asociados al movimiento de las juntastradicionalmente utilizadas en los puentes de vigas.

Esta publicacin explica lo que se entiende por puente integral e indica lastipologas estructurales utilizadas. Un aspecto clave en el funcionamiento de unpuente integral es el desplazamiento impuesto por las deformaciones trmicascclicas del tablero a los apoyos y al suelo retenido por aquellos. Los proyectistasde puentes debern familiarizarse y hacerse expertos en el tratamiento de larespuesta del suelo y las estructuras de soporte ante aquellos desplazamientos.

En la obra se dan indicaciones sobre las bases de proyecto de puentes integralesas como sobre la metodologa que debe seguirse tanto para puentes con estribos


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

xiP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003

de contencin como para puentes con soportes tipo durmiente o con pilaresindividuales.

El uso de pilas de acero en los apoyos permite disponer de un elemento flexiblemuy adecuado para la construccin integral. Su comportamiento bajo las cargasdel tablero y de la presin del suelo se explica cuidadosamente.

Tambin se analizan los requisitos establecidos por la Highway Agency,comparados con otras Normas y Reglas de buena prctica relativas alcomportamiento del suelo.

Se estudia la interaccin entre las rigideces del tablero, soportes y suelo, as comolos requisitos de unin entre aqullos.

A lo largo del trabajo se hace referencia a la publicacines gemelas tituladasPuentes integrales de acero: ejemplo desarrollado para un puente de un vano ePuentes integrales de acero: ejemplo desarrollado para un puente de variosvanos que en una serie de hojas de clculo ponen de manifiesto muchos de lostemas contenidos en esta obra.

ndskrmsbroar i stl: Dimensioneringsvgledning

Sammanfattning

ndskrmsbroar har brjat anvndas i allt hgre utstrckning fr att undvika deunderhllsproblem som r frknippade med rrelsefogarna i traditionellastlbalksbroarna.

Denna publikation frklarar verkningssttet och olika konstruktionslsningar frndskrmsbroar. En frga som tas upp r vad som hnder nr bron utvidgar ochdrar ihop sig i lngsled, p g a temperaturndringar. Brokonstruktren fr hr lrasig att hantera jordtryck och stdkonstruktioner samt allmnt bygga upp kunskapenom denna konstruktionstyp fr stlbroar.

Det ges vgledning i dimensioneringsfrutsttningar och dimensioneringsgng frndskrmsbroar med olika typer av upplag.

Anvndandet av stlplar som broupplag erbjuder en konstruktionslsning som rvl lmpat fr ndskrmsbroar. Det redogrs fr hur stlfundamentet pverkas avlaster frn brodck och jordtryck.

Brittiska Vgverkets krav behandlas och jmfrs med andra standarder ochdimensioneringsregler rrande jordtryck. Interaktionen mellan frstyvningarna avbrodcket, brostden och marken r utforskad och kraven p samverkan mellandem r utredda.

Hnvisningar grs ven till publikationerna Steel integral bridges: Design of asingle-span bridge - worked example och Steel integral bridges: Design of amulti-span bridge - worked example, som illustrerar mnga av de aspekter somomfattas av denna publikation.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

xiiP:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t

1P:\CMP\Cmp657\pubs\P163\P163-Final.wpd 15 September 2003

1 INTRODUCTION

A modern beam-type bridge comprises two essential structural components - a deckto span the gap and the supports. The deck has roadway surfacing, and thatsurface must match against the surfaces of the approach roads at either end. Sincethese bridge structures flex, expand and contract, it has been customary to useseparation joints between the ends of the deck and the approach structures, and toprovide simple bearings on the supporting structures. The object has been not toconstrain the thermal expansion or contraction of deck beams nor to restrain theirrotation at supports.

Multiple span bridges can then be formed from a series of simply-supported beams,with similar separation joints between the ends of the separate decks - this wasparticularly popular in construction in reinforced concrete. However, structuralcontinuity over intermediate supports has always been easy to achieve withcomposite decks, and this has little effect on the support structure, other than aredistribution of the vertical reactions, but it does afford some economy in the deckconstruction.

The consequence of providing simple support details and separation joints is thatthe abutting interface between bridge road surface and approach surface sees arange of movement as the bridge temperature changes. For very small bridges thiscan be accommodated by a narrow gap that opens and closes, but for larger bridgesa fabricated movement joint must be provided, so that the gaps are never largeenough to cause a hazard to the road users.

The structural form of a beam-type bridge with movement joints may be contrastedwith that of a traditional masonry arch. The arch will change its shape slightlyunder load as it springs load in compression to the abutments, but the roadwayis effectively continuous, laid on approach road base foundations and then on fillover the arch barrel. Such structural deformations as occur are accommodatedwithin the fill, road base and surfacing materials. With a masonry arch bridge,there is no gap, no discrete interface, no relative movement between the bridgeroadway and the approach roadway, because the arch, its abutments and the soilbehind all act together, or integrally.

With beam-type bridges there have been many problems in practice with leakingjoints, both over intermediate supports and at end supports, leading to poordurability and consequent high maintenance costs. As a result, the HighwaysAgency (HA), would like to see greater use of integral construction i.e. withoutmovement joints, particularly for bridges shorter than 60 m.

This publication is based on findings from studies carried out by the SCI for BritishSteel(1); it provides an introduction to the concepts relating to integral bridges andillustrates ways in which the ordinary composite beam-and-slab deck bridge can beadapted to become an integral bridge. Also, the opportunity to use steel in placeof reinforced concrete for the supports is explored. Steel piles offer a degree offlexibility at supports that is particularly suited to the movements that occur in anintegrated structure; guidance is included to facilitate the consideration of steelpiled substructures. Reference is made throughout to two companionpublications(2)(3) that illustrate by worked examples many of the design aspectscovered in this publication.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


2 WHAT IS AN INTEGRAL BRIDGE?

2.1 Definition and terminologyGenerally, an integral bridge is one where the bridge deck is made without anymovement joints at the abutments or between spans. The use of the terms integralbridge, integral abutment and integral construction have not been consistent todate and the extent of the integrity between the deck and supporting structurevaries. To avoid confusion a more rigorous system of definition is required.

Bridges without movement joints can be conveniently divided into two basic classes,termed integral, and jointless deck. The difference between the two, and theprincipal features of various forms of each, are explained below.

The use of the term integral abutment is avoided in this publication, except whenreferring to its use in the USA.

The term endscreen, or endscreen wall, is used in relation to both integral andjointless deck bridges to describe the stub wall at the end of the deck that retains theadjacent road construction.

2.1.1 Integral bridgesAn integral bridge is one that has structural continuity between the deck and thestructural elements that support it. There is no relative translational movement atany interface between the deck and the supporting structure.

Three forms of integral bridge are described in this publication - frame abutment,pinned and bankseat, described in Sections 2.2, 2.3 and 2.4 respectively.

2.1.2 Jointless deck bridgesA jointless deck bridge differs from an integral bridge in that movement bearingsare provided between the deck and the substructure that supports it, ensuring thatthe supporting elements are not subject to displacement as a result of thermalexpansion/ contraction or of deflection under load.

2.1.3 SupportsIntegral bridges can have wall abutments, column piers or bankseat supports orcombinations. The foundations can be either spread footings or piles. Conventionalabutments comprise retaining walls where either concrete types or sheet piles areused. Other types of abutment include pier abutments that are essentiallyfall-through column abutments with endwalls and side slope configurations.

2.2 Frame abutment integral bridgesThe frame abutment integral bridge is a fully integral bridge with the abutment wallsworking integrally with the soils that surround them (and thus derive some of theirresistance from them to lateral loads in bending). In addition, the supportingelements carry the axial loads which are the end shear forces from the deck beams.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial is

cop

yrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


Sway restraint is provided by the soil between the 'foundation' and the top of theframe abutment but the degree of restraint is dependent on the soil characteristicsand the geometrical configuration of the supporting element.

To illustrate the effects that must be considered in the design of the fully integralbridge, a diagrammatic illustration of the deflections due to a temperature increaseand due to live loading on the bridge are given in Figures 2.1 and 2.2. Noparticular form of foundation is shown in order that the diagrams can be taken torepresent either a wall on a strip or spread footing, a wall on a pile cap foundation,or the upper part of piles driven to a greater depth.

Figure 2.1 Integral bridge - displacements due to expansion

Figure 2.2 Integral bridge - displacements due to vertical loading

No intermediate support is shown in these Figures. A configuration withintermediate supports would behave in a similar manner at the end supports and theprinciples illustrated would not be affected. For further comments on the behaviourat intermediate supports, see Section 2.6.4.

2.3 Pinned integral bridgesIn a frame abutment integral bridge, displacements due to temperature (thermalstrains) and load on the deck induce reverse curvature at the head of the abutmentwall, as shown in Figures 2.1 and 2.2, and adequate moment capacity is requiredin the connection. This can involve a complex reinforcement detail in reinforcedconcrete endwalls and capping beams to ensure moment and force transfer.

The introduction of a pin at the connection between the deck beams and anabutment removes these large hogging moments at the bridge end. This can beefficient where there is judged to be little to be gained from an integral connection.Such a pin can be achieved with a relatively simple pinned bearing; the detail ofhow this may be achieved is discussed in Section 5.3.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


The effects of introducing a pin on the deflections of the bridge structure isillustrated diagrammatically in Figure 2.3.

Figure 2.3 Pinned integral bridge - retaining wall displacements due todeck thermal expansion

2.4 Bankseat integral bridgesA bankseat support structure is a common detail for highway bridges. A bankseatcan be made part of an integral bridge by fully connecting it to the deck to makethem structurally continuous. Since a bankseat only sits on the soil, the structurefoundation will move relative to the ground as a result of thermal expansion andcontraction, and can rotate under deck loading.

Such a bridge can be formed by an endscreen wall (across the ends of the deckbeams) that has a footing foundation, thus combining the functions of verticalsupport to the deck and lateral support to the abutting road construction.

A diagrammatic illustration of the deflections due to temperature and load effects ona bankseat integral bridge is given in Figure 2.4 and Figure 2.5.

Figure 2.4 Bankseat integral bridge - displacements due to expansion

Figure 2.5 Bankseat integral bridge - displacements due to verticalloading


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


A key aspect to note is that the foundation face which bears on the ground can slideon the soil under certain combinations of loading (that include significant thermalstrain) and may also rock as the deck deflects under live loading. Depending on thesoil type, the soil may be affected by these cyclic movements, and the possibility ofdegradation of the bearing strength needs to be taken account of in deciding apermissible bearing pressure. Long term settlement could result beneath such bridgeends. Therefore bankseat integral bridges should only be used where the soils havehigh strength, and the total length of the bridge is small (short bridges have lesserend movements and rocking under load).

2.5 Jointless deck bridgesAs explained in Section 2.1.2, a jointless deck bridge eliminates movement jointsat the road surface, but the supports are not integral with the deck structure.However, like a bankseat integral bridge, an endscreen wall is formed across theends of the beams, presenting a vertical face to support the abutting roadconstruction.

An arrangement of a jointless deck bridge on a bankseat support is shown inFigure 2.6. Vertical loads are carried directly in bearing onto the soil. There is amovement interface between the deck beams and the support, arranged as a narrowhorizontal gap under the endscreen wall (see Section 5.4 for further details).

Sliding bearing

Figure 2.6 Jointless-deck bridge - bankseat support

An arrangement on a piled support is shown in Figure 2.7. A suitable detail wouldneed to be provided at the bottom of the end wall, which moves relative to theground beneath, so that any drainage water is conducted away from the piles.

Sliding bearing

Figure 2.7 Jointless-deck bridge - piled support

Like conventional non-integral bridges, access must be provided to permit inspectionof the bearings during the life of the bridge and provision made in the constructionto allow for jacking up the deck for bearing replacement. The principal feature istherefore the absence of deck joints.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


2.6 Additional considerations when choosingintegral construction

2.6.1 The deck-end/road construction interfaceThe degree of restraint provided by the soil and road construction against anendscreen face to a deck, to the retaining wall or piles, may reduce but can nevereliminate expansion and contraction movements due to thermal strains in the bridgedeck. Indeed, studies(1) show that a significant proportion of the free thermalmovements still take place in an integral bridge deck. It is therefore futile to try tocompletely restrain such thermal movements by attempting rigid abutment design.

Where the bridge deck length is small, thermal movements can be accommodatedat the bridge ends by an asphaltic plug joint in the road surface immediately behindthe end of the bridge. The joint can be expected to perform elastically withoutcracking. However, when deck lengths and movements are larger, cracking is likelyto develop in the road surface in the joint area, allowing salt-laden runoff water topercolate down the back of the structure.

Opinions vary as to the effectiveness of asphaltic plug joints but the prudent bridgedesigner should pay attention to detail at the buried end of the deck and makeprovision for surface water leakage regardless of the claims about so-called elasticbehaviour of joints. The difference in vertical stiffness between the road and theend wall will concentrate any movement at the junction. Consequently, the surfacerun-off on the road will doubtless find its way through cracks to the back of theabutment wall. There is a concern for the maintenance authority that anydeterioration that results will be entirely hidden and un-inspectable.

For bridge lengths in excess of about 10 metres it is therefore perceived to bedifficult to produce a totally satisfactory and durable joint at the junction of theendscreen wall and the road construction.

2.6.2 Approach slabsThe problems described in Section 2.6.1 can be moved away from the end of themain deck structure and supports by the use of an approach slab and this has beena standard detail in the USA. However the practice has had mixed success on somebridges in the USA(4) and in Scotland(5). Failures appear to be mainly due to theinadequacy of the connection between the slab and the end wall. Clearly, such aslab must have structural ties to the deck end and be properly keyed to the structureso that they move together, and will need to be designed with sufficient strength inbending that it can span over any local settlement due to traffic vibration.

Thermal deck movement can cause longitudinal compression in the approach slabor associated heave of the underlying fill due to lateral displacement of the endscreenwall or abutment wall, and this can compound the other problems identified andexplained in the above references(3).

The arrangement of an approach slab is shown diagrammatically in Figure 2.8.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


Integralbridgedeck

Road surface

Road base

Approach slab

Steel bearingpiles

Asphaltic plug joint

Select granularfill

Embankment fill

Figure 2.8 Typical arrangement of an approach slab as used in the USA

The maintenance problem at the joint is transferred from the bridge structure to theroad construction with an approach slab, but it is possible that two structuraljunctions are created at the changes in stiffness between deck/approach slab andapproach slab/road construction. Due to the likelihood of cracking at eitherjunction, it is considered that provision must be made to collect any surface waterthat could percolate through such cracks at both, and to lead it away from theadjacent bridge structure.

Any leakage at the movement joint can be captured by transverse drains at roadformation level and led away to the normal carriageway drainage system that isremote from the structure, but careful attention to detail of the bridge end shape isnecessary to make such provision really effective.

Approach slabs have not been favoured by the Highways Agency for use in non-integral bridges because of a poor track record. Their preference seems to be toconcentrate on the use of controlled backfills to bridge end-walls and attention tocareful compaction to prevent settlement. Whether this proves to be effective forintegral bridges remains to be seen.

2.6.3 Retained and unretained approachesThe clear opening provided by a bridge or by the end span of a multi-span bridgemay either be bounded by a vertical face, or the ground beneath the bridge may besloped upward to the underside of the bridge. Both arrangements are shown in theFigures in this Section and either can be used, regardless of whether the bridge isapproached by embankments or spans across a cutting.

When the opening is to be bounded by a vertical face, the length of deck isminimised, but a retaining wall is needed to support the road formation and theunderlying fill or the soil face in a cutting. Conventional arrangements are toprovide either a reinforced concrete wall or a steel sheet pile wall and to support thedeck beams on top of the wall capping beam.

When a retained configuration is to be incorporated into an integral bridge, there isa choice as to whether the supporting and retaining functions are separated orcombined. If they are combined, the head of the retaining wall is subjected to deckthermal displacements and this complicates the retaining wall design.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


Alternatively, if the approaches are not retained and have natural earthworks slopesor reinforced earth slopes instead, column-pile integral bridges and jointless bridgescan be used with bankseats on footings or on piles as already described.

For motorway or trunk road replacement bridges, individual steel bearing piles orsheet pile walls can be driven through the existing embankment fill or cutting faceto found on deeper soils before any new earthworks are started.

For new integral bridges on green-field sites, steel column-piles can be driven toprovide an upstanding length of column as an alternative to conventional concreteconstruction; this can save site occupancy time.

2.6.4 Intermediate supportsIn the preceding definitions and Figures, the bridge is taken to be a single span forsimplicity. Many bridges, however, are of more than one span. Clearly, to beintegral, the deck beams must be continuous over any intermediate supports, butthis arrangement is already quite normal for composite construction. However,there remains the question of whether the behaviour of intermediate supports has anyeffect on the overall integral behaviour.

If the intermediate supports are provided with sliding bearings offering no rotationalrestraint, then clearly they will have no effect on the deck behaviour due totemperature change. If the supports are pinned to the beams (but still with norotational restraint) - perhaps in order to offer restraint to the support againstcollision loads - then they will be displaced by deck thermal strains unless it is thecentral support to a symmetrical bridge configuration. This displacement is shownin Figure 2.9.

Generally, thermal movements will be proportional to the distance from a nullpoint in the middle of the bridge, but if the spans are unsymmetrically disposed, orif the stiffnesses at the ends are unequal, the null point will not be central.

Figure 2.9 Displacement of intermediate supports pinned to deck beams

Intermediate columns that need to be designed to resist vehicle collision loads canbe more effective when they are restrained at the top by the bridge deck, perhapsthrough a crossbeam. Unless they are at the null point, the deflections due tothermal movements will then have to be taken into account in the column design.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


3 WHY CHOOSE AN INTEGRAL BRIDGE?

3.1 Experience with non-integral constructionOver the past thirty years, engineers have become more aware of the pitfallsassociated with the use of expansion joints and expansion bearings.

C Joints are expensive to buy, install, maintain and repair; repair costs can be ashigh as replacement costs.

C Successive carriageway repaving will ultimately require that joints be replacedor raised.

C Even so-called waterproof joints will leak over time, allowing runoff water,often salt-laden, to penetrate through the joint and thus accelerate corrosiondamage to girder ends, bearings and supporting substructures.

C Accumulated dirt, stones and rubbish may fill recesses, which can, for example,lead to failure of elastomeric bearing glands.

C Hardware for joints can be damaged and loosened by snow ploughs and heavytraffic.

C Bearings are expensive to buy and install and costly to replace. C In time certain types of steel bearing may tilt and/or seize up because of loss

of lubrication or build-up of corrosion.

C Elastomeric bearings can split and rupture as a result of unanticipatedmovements, or ratchet out of position.

C Seized expansion joints and malfunctioning expansion bearings can also lead todamage of the main structural members.

In 1985 in the USA, a survey carried out by the Federal Highway Administrationfound(6) that 75% of the bridges built using expansion joints and bearingsexperienced movement contrary to their designers intent. The survey report pointedout that vertical movements were noticeably greater than horizontal movements,where the magnitudes of these vertical movements in many instances were due to theinward movement of the abutments.

In the UK, a survey was carried out by Maunsell and Partners for the Departmentof Transport in 1989. The report of that survey(7) identified a number of factorswhich contributed to the inadequate durability of many bridge structures. The mostserious sources of damage were found to be salt water leaking through joints in thedeck or service ducts and poor or faulty drainage systems. Also, damage occurreddue to splashing or spraying of salt water from de-icing salts on to bridge abutments,piers, parapet edge beams and deck soffits. Poor workmanship was found to be anextremely frequent problem. Most critical was the failure to achieve the specifiedconcrete cover to steel reinforcement. This led to deterioration, particularly whenit occurred in association with joint leakage. Cracking was the other main problem,particularly that due to early thermal effects.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


3.2 Highways Agency requirementsBased partly on the findings of the Maunsell report, the Highways Agency publishedtheir Standard, BD 57/95 Design for Durability and the accompanying Advice NoteBA 57/95(8). BD 57 specifies that bridges with lengths not exceeding 60 m andskews not exceeding 30E shall ... be designed as integral bridges ... withoutmovement joints for expansion or contraction.

That Standard is concerned mainly with the Agencys principles of design; detailsof the Agencys advice on the design of integral bridges are given in their AdviceNote BA 42/96 Design of Integral Bridges(9) that was published in November 1996.See Sections 7 and 12 for further discussion on BA 42/96.

3.3 Advantages of integral bridgesClearly, the first advantage is the elimination of the cost of, and additional workassociated with, the provision of movement joints at the ends of the bridge. Thisadvantage is confirmed by experience in the USA (see Section 4), where it wasfound that the initial capital costs of integral bridges were cheaper than bridges withexpansion joints, even when the extra work associated with ensuring structuralcontinuity were taken into account (see Burke(10)).

The benefits of reduced maintenance costs and reduced risk of damage arising fromleaky joints is less quantifiable, but is probably the major benefit in most cases.

Apart from these two principal advantages, other benefits can be seen, dependingon particular circumstances and configurations. These include:

Substructure design

The restraint to retaining wall abutment structures provided by the deck (which canact as both a prop and a rotation restraint) can lead to economies in the wall design.

Resistance to accidental and seismic loadings

The increased longitudinal restraint to the deck, and in frame abutment integralbridges, the moment restraint, provide extra load paths against the effects ofaccidental and seismic events. In particular, where seismic loading is a significantconsideration, considerable savings can be achieved by avoiding the need forenlarged bearing seat widths and restraining devices.

Torsional restraint of deck at supports

Substantial endscreen or abutment walls ensure that all the deck beams, and the fullwidth of wall, rotate equally and thus tend to distribute loads more evenly betweenthe deck beams.

Faster construction

With piled abutments, only vertical piles are needed (no rakers), which bothsimplifies and speeds construction. Where permanent bearings are omitted, a time-consuming operation is eliminated.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


Tolerance requirements reduced

The close tolerances required for setting expansion bearings and joints areeliminated. (Although other tolerance requirements may be introduced, dependingon the connection detail).

Greater end span ratio ranges

It is normal practice for non-integral bridges to limit the ratio of the end-span lengthto that of the adjacent span to approximately 0.6, to avoid the occurrence of upliftconditions under extreme loading; if uplift can occur, expensive hold-downarrangements will usually be needed. The continuity at the ends of a fully integralbridge automatically provides uplift restraint; even a compact integral bankseat detailacts as an additional counterweight.

Other advantages are listed by Burke(10), such as the elimination of the risk ofleakage at the ends, which is of particular benefit with girders of weathering steel.Such girders in non-integral bridges commonly need to be painted at the ends foradded protection.

3.4 Practical aspects of the site that influencechoice

The main practical factors influencing the choice of an integral configuration are:

C The overall length of the bridge.C The geometrical arrangement of the end supports (e.g. whether there are side

slopes, cut or fill earthworks).

C The type of soil(s) on which the bridge is founded.C The practicality of replacing bearings and access for maintenance.C The retained height of fill.C The construction method to be used.

Where the bridge is a replacement, or is built over an existing road, speed and easeof construction will also have an important influence on the choice. This isparticularly so where lane rental charges apply and traffic disruption cost has to beconsidered. Advances in steel bridge design and construction are providing bridgeengineers with deck structures that can be fabricated to a large extent off-site andtherefore require less time for erection. It is therefore logical to develop anyapplications of steel for the support elements of the integral bridge that can alsominimise site occupation time.

When electing for an intermediate support to the bridge, the need to make use of thedeck to provide restraint to the top of the support to assist in resisting collision loadsis an important factor in detailing the structural framing and the connections. Thesuitability of concrete, steel or composite construction at the connection will be animportant consideration at all supports. In addition, a more economic substructuremay be possible by considering compliant steel piled supports.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


3.5 Whole life costing In BD 36/92(11), the Highways Agency requires that, in comparing alternativedesigns for bridges, the whole life cost is considered, i.e. the capital cost plus thedirect and indirect costs of maintenance throughout the life of the structure. Sincethis Standard predates both BD 57/95(8) and BA 42/96(9), there is no mention ofintegral construction in it, but it would seem sensible that the choice betweenintegral and non-integral construction should be considered in the same way.

The savings in whole life cost by choosing an integral bridge concept can be:

C Reduced construction cost.C Elimination of the cost of maintenance and replacement of movement joints.C Elimination of the cost of maintenance and replacement of bearings (where they

are omitted, or a reduced cost where simpler bearings are used).

C Reduced allowance for the maintenance cost for the deck slab (because theworst potential source for deck reinforcement corrosion is eliminated).

Note that it is not entirely necessary to eliminate bearings to reduce maintenancecosts. For example, simple steel rocker or knuckle bearings provide an effectivepinned connection, but do not need anything more than an occasional clean andrepaint as there are no moving parts that can seize up. Further information isgiven in Section 5.6.

3.6 The use of steel piles in integral bridgesSteel piling can be used for elements in substructures and foundations for integralbridges, such as:

C Bridge abutments.C Intermediate piers.C Wing walls.C Retaining walls.

Steel pile sections have been used successfully in non-integral bridges in the UK andelsewhere in the world and provide a prefabricated, high quality foundation ofknown structural integrity that fulfils the requirement for minimum constructiontime. Not only can piles be driven rapidly in the vast majority of soil types but theyare capable of being loaded immediately, which is a distinct advantage in fast-trackconstruction projects.

The advantages of steel piling are described in the Steel bearing piles guide(12) andmay be summarised as the follows:

C Construction is significantly quicker when compared to in situ reinforcedconcrete foundations.

C There is no requirement to excavate for foundations.C There is no disturbance of the existing ground during piling.C The steel components are shop quality not site quality.C Piles can easily be made aesthetically pleasing.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


C Piles can be placed in advance of other works.C Piles have immediate load carrying capacity.C Sheet pile walls provide a curtain walling to contain the working site.

3.6.1 Structural advantages of piling in integral bridgesFor integral bridges, steel piling provides a sufficiently stiff but flexible structuralelement in the substructure for integral bridges. It offers a compliant foundation thatwill not crack in bending and that can reduce retaining wall bending moments,relative to a rigid reinforced concrete alternative.

Compliant is a term that neatly summarises the characteristics of steel substructuresthat are beneficial to integral bridge behaviour.

3.6.2 Types of bridge with steel pilingDifferent types of frame abutment, pinned and bankseat integral bridge areillustrated in Figure 3.1.

Tubular column-pile pier Tubular column-pile pier

Retaining wall Retaining wall

BankseatPinnedFrame

Carriageway CarriagewayPiled bankseat

Figure 3.1 Types of integral bridge with steel piles

Some types of jointless bridge with steel substructures are illustrated in Figure 3.2.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial is

cop

yrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


BankseatCantilever/Propped

Retaining wall

Tubular column-pile pier

Carriageway

Slidingsupport

Flexible seal

H piles

Figure 3.2 Types of jointless bridge with steel piles

3.6.3 Appearance of piled substructure of integral bridgesSteel piles for bridges can be very dominant features on the urban and rurallandscape. Careful design can make a considerable improvement to their appearancewithout leading to a significant increase in cost.

Apart from having to satisfy the functional requirements, steel piling can be madeto blend in with its surrounding environment as far as possible and to beaesthetically pleasing. The aspects that are important are:

C Height of abutment/pier and inclination of its front face.C Anchorages in the face.C Wing wall angle of return affecting the elevation of the wall.C Gradient and surface treatment of the adjacent ground.C Surface textures and paint colour of the facing walls, and the expression and

position of vertical and horizontal construction joints.

C Concrete footing walls.C The coping/capping beam of the abutment.

The appearance of a pile can be improved by providing features in the finished faceor by decorative facings or claddings.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


4 HISTORICAL BACKGROUND

4.1 Integral bridges in Europe and the USABridges where joints within the deck of the bridge are omitted are not new conceptsin design. In some countries it has been usual practice to build bridges withoutjoints, and bridge spans longer than 100 m have been built. There are nowexamples of modern integral construction in many countries including Australia andSweden, but the country with the greatest experience to date is the USA. Only afew integral bridges have been built in the UK.

In Sweden, bridges are built without expansion joints and even withouttransition/approach slabs. Various integral bridge types are in use without specialabutments in the embankments. Single-span slab-frame integral bridges have beenused for over 50 years and the longest continuous slab-frame bridge was one builtin 1968 which had five spans and a total length of 120 m. Sweden has theadvantage of rock foundations that permit the generation of stiff reactions to restrictbridge movements.

4.1.1 Examples of integral bridges in the USAIn the USA, the move towards integral and jointless construction has led to amuch greater use of continuous construction for multiple spans (it is now favouredby over 85% of state transportation departments) and to the design of integralabutments (fully integral and semi-integral bridges in our terminology). Experienceon the performance of integral bridges constructed in the USA is reviewed in apaper by Burke(4).

The terminology used to describe the types of integral bridge in the USA, however,differs from the definitions proposed in Section 2 of this publication. Althoughsimilar concepts have been used, the lack of rigour in definition of bridge type canlead to some confusion.

Generally, the US design of integral abutments appears to have been somewhatempirical, based on what is judged to have worked satisfactorily before, rather thanby rigorous analysis. The latter would demand more understanding of the behaviourof such structures so that it can be incorporated into a design procedure.

Most of the integral abutment details described in journals and other publishedpapers involve the use of piles (normally steel H piles) to carry the vertical reaction.A typical configuration is that used in Tennessee(13), as shown in Figure 4.1. Steelbearing piles are cast into the abutment and provide flexibility under lateraldisplacement.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


H piles

Bearing

ReinforcementPrestressedconcrete beamsSelected

granular fill

Drainageaggregate

Figure 4.1 Tennessee integral abutment detail

The introduction of rotational continuity can generate high bending stresses in theabutment detail, and this is either accepted or Freysinnet hinge details wereintroduced into the reinforced concrete wall. Examples of severe cracking andsplitting have been documented at Freysinnet hinges and the long term durabilityof the integral abutment details used is not known.

The use of coated reinforcement bars appears to be normal procedure for suchabutments in USA now because they are concerned about the durability aspects ofspalled concrete cover. However, the design life for bridges in the USA is only 50years(14). Consequently, care should be exercised before adopting any reinforcementdetails or connection details from US practice.

Figure 4.2 Freysinnet concrete hinge detail (ref. Ohio detail(15))

A region of potential weakness in a variety of integral abutment details is the keyingof the abutment to the deck slab or to the approach slab. Failures of inadequatedetails have been reported in the USA(16). The evidence suggests that the design ofthe connection must include very careful design and detail of the tyingreinforcement. To do this effectively requires a better fundamental understanding


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


of how connections work and of the stress distributions involved than is presentlyavailable in the USA.

Many lessons can be learnt from the US experience. Burke(4) has identified a list ofdesign recommendations to assist an engineer considering an integral bridge design.These have been considered in Section 3 of this Guide. Skew integral bridges

A nationwide survey in the USA has shown that skewed and curved integral bridgeswhere the deck is rigidly connected to the supporting wall structure are common,and Greiman et al(17) summarized the findings of a survey of the HighwayDepartments of all 50 States to obtain information on the design and performanceof skewed bridges with integral abutments. It was found that there was a lack oftheoretical and experimental research in this area(18)(19), with the result that moststates designed integral abutments on skewed bridges on the basis of empiricalexperience without adequate theoretical analysis.

4.2 Examples of integral bridges in the UnitedKingdom

Portal bridges with monolithic abutments have been built in Britain - perhaps thebest known are the twin span concrete overbridges on the original section of the M1motorway, designed by Sir Owen Williams & Partners in the early 1960s. Thistype of construction is particularly massive and was not adopted on later motorways.

Recent examples of integral bridges include the Stockley Park Canal bridge nearHeathrow Airport; the A41 Stone Bridge, Aylesbury, Buckinghamshire; the ChadBrook Bridge in Suffolk; the Bridgend-By-Pass overbridge; that all used steel piledsupports. Several others are currently being constructed.

The above named bridges all have reinforced concrete decks, but their featuresnevertheless illustrate general principles that are applicable to both concrete andcomposite deck bridges. The principle features are described below.

Stockley Park Canal Bridge

The Stockley Park canal bridge (Figure 4.3) has a clear span of 19 m and wasdesigned as an integral bridge such that the mid-span bending moment was aminimum, in order to provide adequate canal traffic head clearance without raisingthe road elevation. The deck is monolithic with the reinforced concrete abutmentwalls, and live loads are carried by transferring moments into the abutments. Theabutments are founded on a single line of 600 m diameter steel tubular piles that areembedded in the abutment retaining end wall. This has been designed by includingthe rotational stiffness of the abutment fill in the overall stiffness of the bridgestructure. The design concept assumed that the abutment fill not only acted as aload on the abutment but also provided an additional component of restraint in thebridge structure. This example of an integral bridge demonstrates an elegant formwith construction economies. Further information is given in a paper by Low(20).


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


LC

LC Canal

19m

600 tubular bearingpiles @ 1700 centres

Figure 4.3 Stockley Park canal bridge

A41 Stone Bridge, Aylesbury, Buckinghamshire

The replacement to the A41 Stone Bridge just north of Aylesbury (Figure 4.4) hasa single span of 18 m over the River Thame. The new bridge was designed as anintegral bridge. The integral bridge arrangement permitted increased freeboard tothe river when in flood, whilst maintaining the existing vertical alignment of theroad over a low floodplain. This avoided the further expense of associatedroadworks. To provide the required freeboard, it was necessary to minimise thedeck beam construction depth to just 600 mm. This was achieved by mobilisingabutment fixed-end-moments to reduce the bending moments at mid-span. Thedeck was propped at mid-span during its construction and then connected tomoment-carrying in situ concrete capping beams on sheet piled abutments.Permanent High Modulus steel sheet piling was chosen to provide a compliantretaining wall foundation of adequate stiffness and to enable a practical constructionprocedure that permitted construction in the dry with minimal excavation in the softalluvial soils. A paper by S. Griffiths of Buckinghamshire County Councildescribing design and construction aspects of the replacement bridge is to bepublished in The Structural Engineer in 1997.

21490

In-situ reinforced concrete deck slab

Precast deck beams

Concrete pile cap

17900

formed from 914x305 UBwelded to sheet pile facing wall

High modulus pile web

Figure 4.4 A41 Stone Bridge, Aylesbury

A134 Chad Brook Bridge, Suffolk

Another example of a replacement integral bridge is that constructed over ChadBrook in Suffolk (Figure 4.5). In this case the bridge span is approximately 11 m.The configuration of the bridge is similar to the A41 bridge in Aylesbury in whichsteel sheet piled abutments are provided and where the pile head is integral with thebridge deck end capping beams. However, on this site steel box beams wereprovided for deck beam support. The sheet piling permitted construction in the dry


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial is

cop

yrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


and the span to be reduced to a minimum. Further information pertaining to thisbridge can be found in a paper(21) by McShane.

10.90m square spanRoad level Reinforced concrete deck

Extent of sheet pilewing wall

Box pilesforming portal

Grass block pavingto stream banks

21 Extent of

bank facing

Figure 4.5 A134 Chad Brook Bridge, Suffolk

Bridgend-By-Pass

The Bridgend-By-Pass railway bridge is a twin 25 m span replacement frameabutment integral bridge on steel sheet pile abutments and with an H-piled centralreservation pier built for Railtrack plc. The abutments are constructed in Larssen 6sheet piles of approximate length 22 m. A reinforced concrete capping beamprovides the connection between the sheet piles and the reinforced concrete bridgedeck.

4.3 Offshore experience with tubular hollowsections

Structural steel circular hollow sections have been used extensively in the UKoffshore oil and gas industry over the last 25 years. During that time, a technologyhas been developed which, through experimental research and testing, has producedindustry accepted practice and enabled codes, standards and guidance to be writtenand comprehensive design procedures to be developed. The leading codes ofpractice have been the American Petroleum Institute codes of practice (API) whichare being updated constantly to embody technical developments in the Oil and GasIndustry. The code of practice relevant to steel structures is API RP2A(22) whichcovers all aspects of design and construction, thereby enabling international designconsultants, fabricators and installation contractors to work to a common standard.

Extensive information is available on circular hollow sections because they arechosen for the major structural components of offshore platforms including the mainsupport columns and legs, bracing and piling. Multi-million pound researchprogrammes have enabled comprehensive tests to be performed to study and simulatethe behaviour of tubular frames. This has included tests to analyse materialstrength, welding, durability and fatigue aspects specific to the environmentalconditions that are present during their in-service life.

Over the past three decades, the offshore industry has invested heavily in R & D intubular steel piling technology. This has included:-

C Instrumented pile load tests in both granular and cohesive soils.C Improved soil investigation methods and tools, e.g. Dutch cone CPTs.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


C Analysis of pile behaviour and calibration of design prediction methods.C International pooling of knowledge and best practice.

This has resulted in consensus amongst practising experts in the profession as to thebest geotechnical design methods to use for tubular steel piles. The methods havea sound theoretical basis but the limitations of theory are recognised by includingempirical adjustment factors. These methods have been validated by the SCI andare presented in the Steel bearing piles guide(12).


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


5 SUBSTRUCTURES FOR INTEGRALBRIDGES

Traditional non-integral bridges have generally used reinforced concrete for thesupports of both composite steel/concrete and reinforced/prestressed concrete deckconstruction. Where piles are needed, both steel and concrete have been usedbeneath abutment walls, bankseats and for intermediate supports.

For integral and jointless deck bridges, both types of deck construction will needdifferent support configurations to respond to the need to accommodatedisplacements due to thermal strain and the bending of the deck.

This Section presents a variety of configurations for supports to each of the typesof integral and jointless deck construction, with particular emphasis on the use ofsteel in the substructure, since that offers a versatile and compliant form that is wellsuited to efficient integral construction. Outline details of supports and connectionzones are illustrated.

5.1 Frame abutment integral bridgesAs explained in Section 2.2 this type of bridge is essentially a simple portal frame,and this means that the end supports will be subject not only to bending due topressure of retained soil and axial load as a result of supporting the deck, but alsoto additional bending as a result of increased soil pressure when the deck expandsand contracts thermally, and to moments and longitudinal forces transmitted to thetop of the wall from the deck.

Initial considerations by the SCI indicated that it would appear difficult to adapt thetraditional reinforced concrete wall-type abutment to accommodate significantthermal displacements and the reverse curvature imposed on a stiff wall. For frameabutment integral bridges the substructure elements need to be compliant inaccommodating displacements due to thermal strain, and steel construction is wellsuited to act in this manner. Consequently, much of this publication concentrateson the use of steel supports, primarily for frame abutment and pinned integralbridges, but also for other types of support, e.g. steel column-piles.

5.1.1 Steel pile retaining wallsSteel sheet piling is commonly used for retaining wall construction in bridges, andis competent to carry the vertical and lateral loading. Where the wall is subject tosignificant bending, High Modulus Piles (UB sections welded to Frodingham sheetpiling - see Section 6) can provide increased stiffness and strength. For both typesof wall the vertical loads and moments are introduced at the top of the wall via asuitable connection detail.

For frame abutment bridges, where significant pile head bending moments will beintroduced by a pile capping beam, High Modulus Piles may be needed for all butthe shortest of bridges.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


Apart from the design of the wall section to carry the forces, the most importantaspect of the substructure to this type of bridge is the analysis and design of themoment connection between the deck and the pile wall abutment. Furtherinformation is given in the companion publications Steel integral bridges: Design ofa single-span bridge - Worked example(2) and Steel integral bridges: Design of amulti-span bridge - Worked example(3).

Concrete capping beam connection

The most versatile method of connecting the deck to a pile wall is a reinforcedconcrete pile capping beam. This is effectively an adaptation of a traditional r.c.capping beam used with sheet pile walls in order to enable moments to betransmitted. The in situ form of construction accommodates the practical tolerancesthat have to be allowed for in the positioning and alignment of the pile wallinstallation and for placement of the deck beams. Capping beam connections canbe used with both composite steel/concrete and in situ/precast concrete beam deckconstruction.

A moment connection for a High Modulus Pile wall is shown in Figure 5.1.

UBSheetpile

Constructionjoint

Reinforcedconcrete pilecapping beam/wall

Concrete deck Asphalticplug joint

Deckbeam

Note:Similar arrangementfor reinforcedconcrete deck beam

High ModulusPile

Figure 5.1 A built-in connection for a High Modulus Pile retaining wall

Effective transfer of moment from deck beams is possible, provided that the concretecapping beam has sufficient moment and torsional capacity to distribute the loadingover the full width of the sheet pile wall. Shear studs, hoops or brackets need to bewelded to the sheet pile and to steel plate girder deck beams in order to ensureeffective transfer of forces (see the Steel bearing piles guide(12).)


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


The connection is formed by using a construction joint within the pile capping beam.This enables the lower part to be cast around the High Modulus Piles and providesa level surface on which to land the deck beams. The reinforcement cage in thecapping beam can then be completed and the concrete upper part cast.

The benefits of using a concrete pile cap beam may be summarised as:

C Effective load distribution from individual deck beams to a group of piles.C Accommodation of a deck girder or beam spacing that is different to the

spacing of the UB sections of the High Modulus Piles.

C Permitting the deck structure interface detail (e.g. holding-down bolts for asteel superstructure or starter bars for a reinforced concrete superstructure) tobe attached to the heads of the piles.

C Accommodation of differences between nominal and as-built geometry of boththe piles and the superstructure. The most serious of these is generally believedto be the position of the piles, but in practice this is not always so - errors ingirder geometry and alignment do sometimes occur.

C Acceptance of a relatively large range of level in pile heads, that can beexpected after trimming to length following driving.

C Construction is unaffected by local damage to pile heads during driving.

As mentioned above, steel pile walls can be used with precast concrete beam decks -an arrangement that has been used is shown in Figure 5.2.

Precast deck beams

In-situ reinforced concrete deck slab

Concrete pile capping beam

High ModulusPiles

Figure 5.2 Concrete beam supported on High Modulus Piles

Steel-to-steel connections

Where the bridge arrangements are such that spacing of deck beam and HighModulus Pile UBs are similar, then individual steel connection details may beconsidered. However, due to positional tolerances, potential fatigue problems, andthe on-site fit-up required, steel-to-steel connections of this type are consideredimpractical at the present time.

5.1.2 Steel column-pilesAs mentioned in Section 2, frame abutment bridges can also be built using individualbearing piles, supporting each deck beam, rather than a retaining wall. Thesecolumn-pile supports are subject to much less resistance from the soil than walls,and they are also more flexible to the lateral displacement due to thermal andbraking loads. Consequently, they attract less induced moment from the deck.


Discuss me ...Cr

eate

d on

06

Febr

uary

200

7Th

is m

ater

ial i

s co

pyrig

ht -

all r

ight

s re

serv

ed. U

se o

f thi

s do

cum

ent i

s su

bject

to the

term

s and

cond

itions

of th

e Stee

lbiz L

icenc

e Agre

emen

t


Steel bearing piles, in the form of box piles or tubular piles, are ideally suited to usein this situation. As part of a frame abutment they will be subject to some inducedmoment from the deck and the detail of this connection will be a very signif

Date post:	21-Nov-2015
Category:	Documents
Upload:	james-mcguire
View:	51 times
Download:	6 times

Integral Bridges

Documents