Download - Ba 82-00 Formation of Continuity Joints in Bridge Decks

November 2000

DESIGN MANUAL FOR ROADS AND BRIDGES

VOLUME 2 HIGHWAY STRUCTURES:DESIGN(SUBSTRUCTURES ANDSPECIAL STRUCTURES)

SECTION 3 MATERIALS ANDCOMPONENTS

PART 7

BA 82/00

FORMATION OF CONTINUITY JOINTSIN BRIDGE DECKS

SUMMARY

This Advice Note gives guidance on the construction ofcontinuity joints in trafficked concrete bridge decks.Only the potential effects of early-age vibration andrelative deflection of the decks are addressed; designmatters such as consideration of creep, shrinkage andsettlement are not within the scope of this document.

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1. Remove IM5, which is superseded by BA 82/00and archive as appropriate.

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Note: A complete new index for DMRB is availablefrom HMSO quarterly.

BA 82/00

Formation of Continuity Jointsin Bridge Decks

Summary: This Advice Note gives guidance on the construction of continuity joints intrafficked concrete bridge decks. Only the potential effects of early-agevibration and relative deflection of the decks are addressed; design matterssuch as consideration of creep, shrinkage and settlement are not within thescope of this document.


* A Government Department in Northern Ireland

THE HIGHWAYS AGENCY

THE SCOTTISH EXECUTIVE DEVELOPMENTDEPARTMENT

THE NATIONAL ASSEMBLY FOR WALESCYNULLIAD CENEDLAETHOL CYMRU

THE DEPARTMENT FOR REGIONAL DEVELOPMENT*

Volume 2 Section 3Part 7 BA 82/00

November 2000

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VOLUME 2 HIGHWAY STRUCTURES:DESIGN(SUBSTRUCTURES ANDSPECIAL STRUCTURES)

SECTION 3 MATERIALS ANDCOMPONENTS

PART 7

BA 82/00

FORMATION OF CONTINUITY JOINTSIN BRIDGE DECKS

Contents

Chapter

1. Introduction

2. Design Issues

3. Safety

4. Construction Requirements

5. Bibliography

6. Enquiries


November 2000


November 2000 1/1

Chapter 1Introduction

1. INTRODUCTION

General

1.1 When a bridge deck is to be widened, built instages or reconstructed in stages, the need to maintaintraffic on the deck may necessitate longitudinalconstruction joints and the use of narrow, typically0.5m - 1.0m wide, concrete in-fill strips. In certaincircumstances, an extension may be cast directlyagainst the deck carrying traffic without using an in-fillstrip, if differential deflection between the existingconcrete and the new deck is small.

1.2 Where construction joints are designed to enablethe completed deck to act monolithically, it is essentialto ensure that the completed structure is not adverselyaffected during the early life of the joint by traffic-induced vibration, deflections and stresses.

Scope

1.3 This Advice Note gives guidance on theconstruction of extensions to bridge decks and in-fillstrips. However, only the potential design issues due toeffects of vibration and relative deflection at theconcrete setting stage of the decks are addressed here;detailed design requirements to counter effects of creep,shrinkage and possible differential settlement betweenold and new parts of the structure are not within thescope of this document.

Implementation

1.4 This Advice Note should be used forthwith forall relevant schemes currently in preparation, providedthat in the opinion of the Overseeing Organisation thiswould not result in significant additional expense ordelay. Design Organisations should confirm itsapplication with the Overseeing Organisation.


Chapter 2

lso if the slump is high, traffic induced vibrationsesult in lower bond and compressive strengths.leeding in freshly placed concrete also may be causedy intermittent vibration during the period of initial set.2. DESIGN ISSUES

General

2.1 The designer should assess and consider thedesign constraints and structural implications that mayaffect the construction of a widened section of a bridgedeck with or without in-fill strips. Importantconsiderations are the volume, composition and speedof the traffic (discussed in chapter 4), consequent trafficinduced vibration effects and differential deflectionwhile fresh concrete is hardening. The designer mustensure that any constraints on construction are clearlystated in the contract documentation.

Detailed Design Issues

2.2 The designer in widening a concrete deck shouldconsider differential deflection effects. This maydirectly affect the decision on whether to:

a. construct the new extension attached to thetrafficked deck or

b. build a parallel deck and construct the in-fill stripas a second stage.

The second is generally preferable, but where the firstmethod is unavoidable, the designer should ensure thedifferential deflection is limited to a maximum of 1mm.

2.3 In calculating the possible differential deflection,the development of the concrete strength and the elasticmodulus and the sequence of removal of shuttering areassociated aspects that need careful consideration. Earlyremoval of shuttering will lead to a higher initialdeflection in all forms of composite construction.Propping can be considered to limit differentialdeflection, but designers must carefully assess thestructural implications.

2.4 Consideration should be given during the designprocess to carry out a dynamic analysis of the structuretaking into account the early life properties of theconcrete coupled with monitoring for deflections andvibrations. The peak particle velocity of the structure inparticular has been found to give an indication of risk ofdamage to immature concrete. As a guide, for concreteless than 24 hours old, it has been suggested thatvibrations during construction should be limited to apeak particle velocity of 5mm per second.

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.5 It should be noted that the theoretical calculationf peak particle velocity is not an easy process. Whereossible and appropriate, vibrations should be measuredn a trafficked deck, in advance or during construction.f this is to be undertaken during the constructionrocess then the contract documents should clearlytipulate the requirement, and due provision should beade to consequent changes to design, construction,

emporary propping and traffic restrictions that maynsue.

ormwork

.6 When in-fill strips are to be adopted theormwork design should ensure that vibration due toraffic is not transmitted at the first stage of paralleltrip construction. This can be achieved in mostocations by keeping formwork independent of therafficked deck.

.7 In order to ensure resistance to vibrations andhe forces exerted by differences in movements, thenfill strip should not be concreted until the new deckas gained sufficient strength. Support to the infill stripay utilise the strength of the existing deck and the

ew deck in most circumstances with suitably placedransverse supports between beams.

.8 In all forms of construction, where peak particleelocity at the construction joint is likely to exceed thepv limit, temporary propping to the trafficked deck orraffic restrictions should be considered. Whereropping is proposed the designer must re-assess thetructural implications. Additional traffic restrictionshould also be considered.

oncrete

.9 Well proportioned concrete mixes are tolerant ofow-amplitude, low-frequency vibrations during theeriod of setting and early strength development.

.10 Laboratory research has shown that high slumponcrete mixes are especially sensitive to segregation.2/1

Mixes with high cement content and low water/cementratio are less prone to bleeding. A reduction in bleeding


Chapter 2Design Issuesmay be obtained by appropriate concrete mix designand the use of admixtures.

2.11 To avoid adverse effects from concrete mixsegregation, reduction in bond and strength, the in-fillconcrete should:

i) be at least Grade 40 or the grade applicable to thenew works, whichever is greater;

ii) have a minimum cement content of 340 kg/m3;

iii) have a maximum free water-cement ratio of 0.4;

iv) have a slump of between 25mm and 50mm;

v) have low bleed characteristics - concrete withbleed water less than 10%, when tested inaccordance with ASTM C232-92 (Bleeding ofConcrete) - Method B, may be considered toexhibit low bleed characteristics.

For special situations other mixes of high early strengthand workability with appropriate reinforcement may beused.

Reinforcement Details

2.12 When the in-fill strip construction method is tobe employed the reinforcement from the existingstructure should not extend into the main body of thenew work, but only into the connecting strip to lap withthe new reinforcement.

2.13 It is preferable not to use hooked reinforcementas voids may develop between the bar and freshconcrete. The other alternative for congested locations,use of reinforcement couplers also should beconsidered. Advice on this subject is available onSpecification for Highway Works, Clause 1716.

2.14 The connection of the reinforcement should beas rigid as possible with longitudinal bars fixed in boththe top and bottom layers of the steel. Thereinforcement should be securely tied at all barintersections.

2.15 Existing concrete shall be removed to exposesufficient reinforcement to provide the necessary bondlength, using suitable tools and minimum force toexpose a sound, even surface to receive fresh concrete.The concrete interface shall be kept wetted for at leastfour hours, but surface water shall be removed withinan hour before placing fresh concrete.November 20002/2


November 2000 3/1

Chapter 3Safety

3. SAFETY

General

3.1 The problems associated with maintaining trafficduring construction include the safety of the public andthe construction workforce. It is preferable to do asmuch of the work as possible prior to the removal ofexisting kerbs and parapets. Details of minimum trafficcontrol standards for construction and maintenanceoperations are given in Chapter 8 of the Traffic SignsManual and Notes for Guidance on Safety atRoadworks. These are minimum standards for normalsituations and analysis should consider each stage ofconstruction. When special complexities or hazardsprevail, additional protective measures should beemployed.


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Chapter 4Construction Requirements

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4. CONSTRUCTION REQUIREMENTS

General

4.1 Experience and research (see bibliography) hasshown that satisfactory joints can be formed intrafficked decks provided that the following factors aretaken into account.

Road Surface Condition

4.2 Because vibrations are primarily the result ofvehicles passing over an irregularity in the bridgeapproach or deck surface, the most effective way toreduce the amplitude of traffic-induced vibrations is tomaintain a smooth riding surface. Particular attentionshould be given to patching potholes and maintaining asmooth transition at expansion joints and temporaryramps.

4.3 Where flexible bearings are employed such aselastomeric type, consideration should be given toinserting temporary packings to limit vertical movementat the support. In such cases due regard should be givento their effect on the overall structure whilst in place.

Traffic Restrictions

4.4 Designers should establish the criteria forcontrolling vehicle speeds and limiting weight in thetrafficked deck adjacent to the fresh and immatureconcrete on the basis of engineering judgement, usingthe guidelines identified in Chapter 2. Generally speedshould not exceed 50 mph during the casting of in-fillstrips or concrete adjacent to the joint and for a periodof 24 hours thereafter. However in many sites the speedrestriction may be more onerous due to safetyrequirements. Provided that attention has been paid tothe adjacent road surface condition it is usuallyunnecessary to impose a vehicle weight restriction forconcrete setting requirements but vibration can beminimised by timing of concreting operations to timesof low HGV traffic.

4.5 Similarly safety considerations will dictate theminimum clearance of vehicles from the edge of theconstruction joint. However, in order to minimisevibrations the wheels of vehicles should be kept aminimum of 600mm from the construction joint. Otherrestrictions may also be necessary in this situation.


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Chapter 5Bibliography

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5. BIBLIOGRAPHY

1. Effects of Traffic-Induced Vibrations on BridgeDeck Repairs - NCHRP Synthesis of Highway PracticeNo. 86, Transportation Research Board, Washington,D.C. 1981.

2. Traffic-Induced Vibrations and Bridge DeckRepairs - Concrete International, May 1986, pp 36-42,Discussion, March 1987, pp 77 & 78.

3. Guide for Widening Highway Bridges - ACIStructural Journal, July - August 1992, pp 451-466.

4. A survey of traffic induced vibrations ACWhiffin & DR Leonard, RRL Report LR 418:1971.


November 2000 6/1

6. ENQUIRIESAll technical enquiries or comments on this Advice Note should be sent in writing as appropriate to:

Divisional DirectorQuality Services Civil Engineering DivisionThe Highways AgencySt Christopher HouseSouthwark Street A J PICKETTLondon SE1 0TE Divisional Director

Director, Road Network Management andMaintenance DivisionThe Scottish Executive Development Department N B MACKENZIEVictoria Quay Director, Road Network ManagementEdinburgh EH6 6QQ and Maintenance Division

Chief Highway EngineerThe National Assembly for WalesCynulliad Cenedlaethol CymruGovernment BuildingsCathays Park J R REESCardiff CF10 3NQ Chief Highway Engineer

Assistant Director of EngineeringDepartment for Regional DevelopmentRoads ServiceClarence Court10-18 Adelaide Street D OHAGANBelfast BT2 8GB Assistant Director of Engineering

Chapter 6Enquiries

CONTENTSINTRODUCTIONDESIGN ISSUESSAFETYCONSTRUCTION REQUIREMENTSBIBLIOGRAPHYENQUIRIES