May 2004 DESIGN MANUAL FOR ROADS AND BRIDGES VOLUME 1 HIGHWAY STRUCTURES: APPROVAL PROCEDURES AND GENERAL DESIGN SECTION 3 GENERAL DESIGN PART 5 BD 60/04 THE DESIGN OF HIGHWAY BRIDGES FOR VEHICLE COLLISION LOADS SUMMARY This Standard gives criteria for the design of highway bridges for vehicle collision loads. It updates and replaces in Part BD 37/01. INSTRUCTIONS FOR USE This is a new document to be incorporated into the Manual. 1. Remove Contents pages for Volume 1. 2. Insert new Contents pages for Volume 1, dated May 2004. 3. Insert BD 60/04 into Volume 1, Section 3, Part 5. 4. Please archive this sheet as appropriate. Note: A quarterly index with a full set of Volume Contents Pages is available separately from The Stationery Office Ltd.
Transcript
May 2004
DESIGN MANUAL FOR ROADS AND BRIDGES
VOLUME 1 HIGHWAY STRUCTURES:APPROVAL PROCEDURESAND GENERAL DESIGN
SECTION 3 GENERAL DESIGN
PART 5
BD 60/04
THE DESIGN OF HIGHWAY BRIDGESFOR VEHICLE COLLISION LOADS
SUMMARY
This Standard gives criteria for the design of highwaybridges for vehicle collision loads. It updates andreplaces in Part BD 37/01.
INSTRUCTIONS FOR USE
This is a new document to be incorporated into theManual.
1. Remove Contents pages for Volume 1.
2. Insert new Contents pages for Volume 1, datedMay 2004.
3. Insert BD 60/04 into Volume 1, Section 3, Part 5.
4. Please archive this sheet as appropriate.
Note: A quarterly index with a full set of VolumeContents Pages is available separately from TheStationery Office Ltd.
BD 60/04
The Design of Highway Bridgesfor Vehicle Collision Loads
Summary: This Standard gives criteria for the design of highway bridges for vehiclecollision loads. It updates and replaces in part BD 37/01.
DESIGN MANUAL FOR ROADS AND BRIDGES
THE HIGHWAYS AGENCY
SCOTTISH EXECUTIVE
WELSH ASSEMBLY GOVERNMENTLLYWODRAETH CYNULLIAD CYMRU
THE DEPARTMENT FOR REGIONAL DEVELOPMENTNORTHERN IRELAND
Volume 1 Section 3Part 5 BD 60/04
May 2004
REGISTRATION OF AMENDMENTS
Amend Page No Signature & Date of Amend Page No Signature & Date ofNo incorporation of No incorporation of
amendments amendments
Registration of Amendments
Volume 1 Section 3Part 5 BD 60/04
May 2004
REGISTRATION OF AMENDMENTS
Amend Page No Signature & Date of Amend Page No Signature & Date ofNo incorporation of No incorporation of
amendments amendments
Registration of Amendments
VOLUME 1 HIGHWAY STRUCTURES:APPROVAL PROCEDURESAND GENERAL DESIGN
SECTION 3 GENERAL DESIGN
PART 5
BD 60/04
THE DESIGN OF HIGHWAY BRIDGESFOR VEHICLE COLLISION LOADS
Contents
Chapter
1. Introduction
2. The Requirements
3. References
4. Enquiries
Appendix A: HGV/Bridge Collision Statistics
Appendix B: HGV/Bridge Collision Photographs
Appendix C: Guidance for Steel and Steel/CompositeBridge Decks
DESIGN MANUAL FOR ROADS AND BRIDGES
May 2004
Volume 1 Section 3Part 5 BD 60/04
Chapter 1Introduction
1. INTRODUCTION
1.1 Accidental collisions of heavy goods vehicleswith the supports and superstructures of highwaybridges occur quite frequently on a national scale.Statistics gathered from such accidents (see AppendixA) show that collisions take place with bridge decks ofstandard (or greater) headroom clearance and on roadsof most categories. Although, so far, only one trunkroad bridge has been completely dislodged by acollision, several footbridges and sign/signal gantrieshave been partly or totally removed from their supportsand hence the potential is there for a major catastropheunless appropriate action is taken both for existingbridges and in respect of future bridges. Appendix Bshows photographs of some collisions with bridges.
1.2 The Department of Transport set up a workingparty to examine ways of protecting existing bridgesfrom large goods vehicle collisions. The working party,which originally concentrated on railway over-bridgestrikes, considered highway bridges. Variouspreventative measures were considered, some of whichwere implemented. The Highways Agency also assessedand strengthened bridge supports that were consideredto be particularly at risk with respect to collision loads;the requirements are contained in BD 48(DMRB 3.4.7).
Purpose
1.3 The purpose of this Standard is to promulgate thecollision loading requirements for new highway bridgesand foot/cycle track bridges, as a revision of AppendixA Clauses 6.8 and 7.2 of BD 37/01 (DMRB 1.3), whichit supersedes [except for the design of certain foot/cycletrack bridge supports (see 2.2)]. For bridges other thanhighway or foot/cycle track bridges, such as railbridges, over a highway, the application of thisStandard shall be agreed with the appropriate authority.The revised loading represents, more realistically, thepossible effects of heavy goods vehicle collisions and isconsistent with other national and internationalrequirements. This Standard contains the loading, broadprinciples for its application and some specificguidelines for design.
May 2004
Sign/Signal Gantries and Lighting Columns
1.4 This Standard does not cover the design of sign/signal gantries, lighting columns or lightweight maststructures such as CCTV masts.
Geotechnical Structures
1.5 This Standard does not cover the design ofgeotechnical structures, such as corrugated steel buriedstructures or reinforced soil abutments.
Implementation
1.6 This Standard should be used forthwith for allschemes currently being prepared provided that, in theopinion of the Overseeing Organisation, this would notresult in significant additional expense or delayprogress. Design Organisations should confirm itsapplication to particular schemes with the OverseeingOrganisation.
Terminology
1.7 For licensing purposes an HGV (Heavy GoodsVehicle) has been recently renamed as an LGV (LargeGoods Vehicle). The term HGV is used throughout thisdocument.
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Volume 1 Section 3Part 5 BD 60/04
Chapter 2The Requirements
2. THE REQUIREMENTS
Vehicle Collision Loads on Highway and Foot/CycleTrack Bridge Supports and Superstructures
2.1 Vehicle collision loads on supports andsuperstructures shall be considered for the design ofbridges as secondary live loads, as defined in BD 37(DMRB 1.3), and shall be applied in Load Combination4, also described therein. No other live load shall beconsidered as coexistent.
2.2 Where bridges over carriageways have supportsof which any part is located less than 4.5m from theedge of a carriageway (see BD 37 (DMRB 1.3) fordefinition) these shall be designed to withstand thevehicle collision loads given in Table 3. Where bridgesupports are located equal to or greater than 4.5m fromthe edge of carriageway, the Designer is required toanalyse the vulnerability of the supports to vehicularimpact. The Designers should use engineeringjudgement and risk assessment techniques to ascertainthe level of risk and vulnerability. Where theassessments indicate that the potential risk of vehicularimpact is severe, the supports shall be designed to thosecollision loads given in Table 3 or appropriateadditional mitigation measures, eg safety barriers, shallbe provided. The Designer’s choice of action in thisrespect and the design collision loads shall be recordedas appropriate eg in AIP in accordance with BD 2(DMRB 1.1). As a general guidance, it is intended thatthe definition of above-mentioned ‘severe potential riskof vehicular impact’ would only apply to special cases
ch as footbridges with single column support, majorng span bridges etc. However, where foot/cycle trackidge ramps and stairs are structurally independent ofe main highway-spanning structure, their supportsay be designed to the loads specified in Appendix Aause 6.8 of BD 37/01 (DMRB 1.3), as shall all bridgepports with a carriageway clearance equal to oreater than 4.5m except where considered vulnerable the Designer and where additional mitigationeasures are not provided (see Table 1). In the case ofulti-level carriageways, such as those encountered inotorway, trunk or principal road interchanges, thellision loads are to be considered for each level ofrriageway separately. Vehicle collision on abutmentsed not normally be considered as they are assumed tove sufficient mass to withstand the collision loads forobal purposes. Where bridges have a headroomearance of less than 5.7 metres plus sag radiusmpensation and deflection of structure in accordanceith TD 27 (DMRB 6.1), the vehicle collision loads onperstructures shall be considered (see Table 2). Theinimum headroom clearance shall be in accordanceith TD 27 (DMRB 6.1). The vehicle collision loads onperstructures are not applicable to the superstructure foot/cycle track bridges, as these are required to haveadroom exceeding the applicable limit to mitigate thefects of their lightweight nature. However adequatestraint on the deck shall be provided to prevent theck being removed from the support under the action vehicle collision forces given in Table 4.
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Volume 1 Section 3Part 5 BD 60/04
Chapter 2The Requirements
Collision loads on supports Clearance from edge of carriageway
< 4.5m ≥≥≥≥≥ 4.5m
Highway bridges:
Piers Table 3 Appendix A Clause 6.8 & Table 15 of BD 37/01
ORTable 3, where applicable and whereadditional mitigation measures are
not provided
Foot/cycle track bridges:
Main piers including ramps and stairs Table 3 Appendix A Clause 6.8 & Table 15of BD 37/01
ORTable 3, where applicable and where
additional mitigation measuresare not provided
Ramps and stairs that are structurally Appendix A Clause 6.8 & Appendix A Clause 6.8 &independent of the main highway- Table 15 of BD 37/01 Table 15 of BD 37/01spanning structure
Table 1: Vehicle collision loads on supports of bridges over highways
Collision loads on superstructures Headroom clearance
< (5.7m + sag ≥≥≥≥≥ (5.7m + sagradius compensation + deflection of radius compensation + deflection of
structure) structure)
Highway bridges: Table 4 Not required
Foot/cycle track bridges: Not applicable Not required
Table 2: Vehicle collision loads on bridge superstructures over highways
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Chapter 2The Requirements
Nominal Loads on Supports
2.3 The nominal loads are given in Table 3 togetherwith their direction and height of application, and shallbe considered as acting horizontally on bridge supports.
Srns
Load normal to the Load parallecarriageway below carriageway
Main load kN kNcomponent 500 1000
Residual load 250 500component (100) (100)
Table 3: Nominal Collision Loads on Su
Note: Figures within brackets are applicable for
Nominal Loads on Superstructures
2.4 The nominal loads are given in Table 4 togetherwith their direction of application. The load normal tothe carriageway shall be considered separately from theload parallel to the carriageway. The loads shall beconsidered to act as point loads on the bridge
sasGetod
Load normal to the Load parallecarriageway below carriageway
kN kN
250 500
Table 4: Nominal Collision Loads on Highway
General Principles
2.5 The intention behind these requirements is thatthe overall structural integrity of the bridge should bemaintained following an impact but that local damageto a part of the bridge support or deck can be accepted.
Supports and Superstructures of Bridges
2.6 Design checks shall be carried out in two stagesas described below:
Stage 1. At the moment of impact. A check is to bemade at ULS only, using the nominal impact loads withpartial factors γfL appropriate to load combination 4. Noother live load is to be included in this check. Local
dtrtalorbsossimmtrmEth
May 2004
upports shall be capable of resisting the main andesidual load components acting simultaneously. Loadsormal to the carriageway shall be consideredeparately from loads parallel to the carriageway.
l to the Point of application on bridge below support
At the most severe point between 0.75 m and 1.5 mabove carriageway level
At the most severe point between 1m and 3m abovecarriageway level
pports of Bridges over Highways
foot/cycle track bridges (see paragraph 2.7)
uperstructure in any direction between the horizontalnd vertical. The load shall be applied to the bridgeoffit, thus precluding a downward vertical application.iven that the plane of the soffit may follow a super-
levated or non-planar (curved) form, the load normal the carriageway may be applicable in either sideways
irection.
l to the Point of application on bridge below superstructure
On the soffit in any inclination betweenthe horizontal and the (upward) vertical
Bridge Superstructures over Highways
amage is to be ignored. It is to be assumed that fullansfer of the collision forces from the point of impactkes place. For the bridge, as in design for all otherad cases, the designer shall determine a likely and
easonable load-path to transfer the impact loads to theearings, supports and foundations (in the case ofuperstructure strikes) or to foundations, bearings orther supports (in the case of support strikes). Eachtructural element in the load-path is to be considered,tarting with the element which sustains the immediate
pact. If it is assumed or found to be inadequate, itay nevertheless be assumed to have effected theansfer to the next element(s) in the load-path, but itust be neglected in carrying out the Stage 2 check.ach element in the load-path shall be considered one same basis. It should be noted that inadequacy at
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Chapter 2The Requirements
this stage is not a cause for concern, since suchinadequacy generally helps to absorb the impact force.In order to prevent the whole structure being bodilydisplaced by the impact, its bearings or supports shallbe designed to be fully adequate to resist the impactloads. Additionally, the Overseeing Organisation mayrequire that certain other elements shall be adequate toresist the impact loads.
Stage 2. Immediately after the impact. Immediatelyafter the event, the bridge has to be able to stand upwhilst still carrying traffic which may be crossing.Since the check is one of survival and the likely trafficis of an every-day intensity, it shall be carried out atULS only but using the partial load factors normallyappropriate to SLS.
Combination 1 shall be used. The partial factors γm andγf3 should take their usual ULS values. HA loading and/or a maximum of 30 units of HB loading shall beapplied for bridges carrying public highways. For thischeck, the designer has to judge what local damagemight reasonably have occurred and must ignoreelements which were assumed or found to beinadequate at Stage 1. If the structure does not satisfythe Stage 2 check then Stage 1 will have to be repeatedwith different assumptions about the adequacy of someelements in the load-path. To justify such amendedassumptions, elements may need to be redesigned toensure their adequacy. Some guidance on possible localdamage and the way impact forces are transmitted inthe case of steel and steel/composite bridge decks isgiven in Appendix C.
Foot and Cycle Track Bridges
2.7 For the design of supports of foot and cycle trackbridges where Table 3 loading is required (see 2.2),robust plinths of 1.5m height shall be provided to carrythe supports and to resist the main and residual loadcomponents given in Table 3 with other appropriateloads in accordance with 2.1. The supports themselvesshall be designed to the reduced residual loadcomponents shown within brackets in Table 3.
Elastomeric Bearings
2.8 For elastomeric bearings, the effects due tovehicle collision loads on supports and onsuperstructures should only be considered at theserviceability limit state. The γfL to be applied to thenominal loads shall have a value of 1.0.
F
2fo(Dap
(a
(b
2/4
oundations
.9 Foundations shall be designed to resist the impactrces transmitted from the collision using BD 30MRB 2.1) and/or BD 32 (DMRB 2.1), aspropriate, with the following qualifications:
) Only ULS checks are required, both for structuralelements and soil-structure interaction.
) When checking against the sliding of the baseand bearing capacity, even for piled foundations,the collision loads shall be reduced by 50% butfull loading shall be considered for checkingagainst overturning.
Chief Highway EngineerTransport DirectorateWelsh Assembly GovernmentLlywodraeth Cynulliad CymruCrown Buildings J R REESCardiff Chief Highway EngineerCF10 3NQ Transport Directorate
Director of EngineeringThe Department for Regional DevelopmentRoads ServiceClarence Court10-18 Adelaide Street G W ALLISTERBelfast BT2 8GB Director of Engineering
Chapter 4Enquiries
Volume 1 Section 3Part 5 BD 60/04
May 2004
APPENDIX A: HGV/BRIDGE COLLISION STATISTICS
A/1
Appendix AHGV/Bridge Collision Statistics
FIG A/1 DISTRIBUTION OF BRIDGE DECK COLLISIONS(England and Wales 1986 - 1990)
Height Clearance
60
50
40
30
20
10
0
Over 5.6m 5.3-5.6m 5-5.2m 4-4.9m Under 4.0m
Rail / B, C, U
Rail / A or M
Foot, Accom / A or M
Road A / or M
Bridge Type
Nu
mb
er
of
Co
llis
ion
s
HGV COLLISIONS (1986 – 1990)
Height Clearance by Bridge Type
Volume 1 Section 3Part 5 BD 60/04
May 2004A/2
Appendix AHGV/Bridge Collision Statistics
FIG A/2 DISTRIBUTION OF BRIDGE SUPPORT COLLISIONS(England and Wales 1986 - 1990)
40
30
Nu
mb
er
of
Co
llis
ion
s
20
10
0
Over 4.5m
3.0- 4.5m
2.0 – 2.9m
1.0 – 1.9m
0.5 – 0.9m
0 – 0.4m
Rail / B, C, U
Foot, Accom / A or M
Rail / A or M
Road A / or M
Bridge Type
HGV COLLISIONS (1986 – 1990)
Width Clearance by Bridge Type
Width Clearance
Volume 1 Section 3
Part 5 BD
60/04
May 2004
APPEN
DIX
B: HG
V/BR
IDG
E CO
LLISION
PHO
TOG
RA
PHS
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Appendix B
HG
V/B
ridge Collision Photographs
PLATE 1 COLLISION OF HGV WITH REINFORCED CONCRETE SUPPORT M20 MOXLEY ROAD BRIDGE(Photograph by kind permission of Director of Highways and Transportation, Kent County Council)
Volume 1 Section 3
Part 5 BD
60/04
May 2004
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Appendix B
HG
V/B
ridge Collision Photographs
PLATE 2 COLLAPSE OF A DECK SPAN FOLLOWING A COLLISION FROM AN EXCAVATOR TRANSPORTED ON A LOW LOADERA2 PARK PALE ACCOMMODATION BRIDGE(Photograph by kind permission of Director of Highways and Transportation, Kent County Council)
Volume 1 Section 3Part 5 BD 60/04
May 2004 B/3
Appendix BHGV/Bridge Collision Photographs
PLATE 3 COLLISION DAMAGE TO REINFORCED CONCRETE CENTRAL SUPPORTM74 LAIRS FLYOVER - B7078
Volume 1 Section 3Part 5 BD 60/04
R STEEL AND STEEL/S
Appendix CGuidance for Steel and Steel/Composite Bridge Decks
C.1 The following guidance on possible local damagein various types of steel and steel/composite bridgedecks is based on advice from the Steel ConstructionInstitute and is being included in this Standard withtheir agreement.
Composite Girder and Slab Bridge
C.2 For a conventional girder-and-slab bridge withintermediate transverse bracing, impact on a bottomflange is likely to cause local plastic deformation andpossibly a small amount of tearing of the flange. Theflange may also be torn locally from the web. Theremay be considerable twisting (rotation) of the flangeabout its line of fixture to the web, or, in some cases, ofthe flange and the web about a line some distance upthe web. If impact occurs at a ‘hard point’ (eg attransverse crossbracing) there may be slightly morelocal deformation than at ‘softer’ positions (eg betweenbracing).
Design against impact for such a bridge could thereforeassume that in Stage 1 the specified impact force iscarried as follows:
(a) Horizontal force is spread from the point ofimpact along the length of the girder, by bendingand shear in the plane of the bottom flange, topoints of lateral restraint, ie at transverse bracing.From such positions it is transferred through thebracing members to connected members. Ifinclined bracing members are present the impactforces will be transferred to the top flanges of thegirders and into the plane of the deck slab. At thesupports the force is carried down through thesupport bracing to the bearings and into thesubstructutre if transverse fixity is provided.
(b) Vertical force is applied upward in the line of theweb and transferred by global bending, of thewhole deck, back to the supports.
(c) Inclined forces are simply resolved intocomponents of horizontal and vertical forces.Local effects from an inclined force on the tip ofa flange may cause only local damage, and thisneed not be checked.
The possibility of damage to more than one main beamshould be considered.
CclifobCrdlowoccprs
Pas
B
Cwteda
Cdfth
Cbthlidsobdc
APPENDIX C: GUIDANCE FOCOMPOSITE BRIDGE DECK
May 2004
.3 For survival in Stage 2, the effect of the damageould be as follows. As a tension element, the flange iskely still to be quite effective. It would be reasonableor a designer to make only a small allowance for lossf effective section although the moment of inertia maye significantly reduced due to the twisting described in.2. However, as a compression element, ie in the
egion close to an intermediate support, the localamage may be sufficient to initiate large deflectioncal buckling, particularly if the flange is torn from theeb locally. It may be prudent to presume the creationf a pin joint in the beam which has been struck andarry out a global analysis accordingly. The shearapacity of the webs should be considered carefully,resuming an ineffective flange and possibly a smalleduction of web area; the effects of web rotation onhear capacity may be considerable.
rovided that the design of the bracing and itsttachment is adequate for the Stage 1 check, therehould be no significant damage to those members.
ox Girder Bridge
.4 For a box girder bridge, local deformation of theeb-flange junction is likely, possibly with minor localaring. If the impact is at or very close to an internaliaphragm or cross-frame, some internal damage maylso result.
.5 In Stage 1 the forces would be transferred byistortional behaviour back to diaphragm or cross-rame positions and then by torsion and bending back toe supports.
.6 Under Stage 2 for mid-span regions there shoulde little reduction in ultimate moment capacity, as fore beam-and-slab bridge; torsional capacity is alsokely to be largely retained. Adjacent to supports theeformation of the web-flange junction will lead toome loss of moment capacity, but it is likely that thether lower corner will continue to provide someending strength. The designer will have to judge,epending on proportions and plate thicknesses, whatapacity might remain.
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Volume 1 Section 3Part 5 BD 60/04
Appendix CGuidance for Steel and Steel/Composite Bridge Decks
Half-through Bridge
C.7 The deck of a half-through bridge will providecontinuous and direct restraint to the bottom flangeagainst impact forces. Some tearing of the bottomflange might occur. If the connection or cross-beamwhich provide U-frame restraint could be damaged bythe impact, then Stage 2 should consider the structuralaction without that restraint at one cross-beam. As forgirder and slab bridges, the effective area of the tensionflange should be reduced appropriately.
