DMRB VOLUME 3 SECTION 4 PART 16 - Standards …

1 VOLUME 3 highway structures: inspection and maintenance SECTION 4 assessmentpart 16Bd 61/10the assessment of composite highway Bridges and structuressummaryThis Standard gives requirements and guidance for the assessment of existing composite highway bridges and structures on motorways and other trunk roads. This is a revised document to be incorporated into Design Manual for Roads and Bridges. It supersedes and replaces BD 61/96 and BA 61 for use1. Remove existing contents pages for VOLUME 3 and insert new contents pages for VOLUME 3 dated June Remove BD 61/96 and BA 61/96 from VOLUME 3, SECTION 4 and archive as Insert BD 61/10 into VOLUME 3, SECTION 4, Part Please archive this sheet as : A quarterly index with a full set of VOLUME Contents Pages is available separately from The Stationery Office manual for roads and BridgesJune 2010design manual for roads and Bridges Bd 61/10 VOLUME 3, SECTION 4, part 16 The assessment of composite highway Bridges and StructuresSummary.

2 This Standard gives requirements and guidance for the assessment of existing composite highway bridges and structures on motorways and other trunk roads. This is a revised document to be incorporated into Design Manual for Roads and Bridges. It supersedes and replaces BD 61/96 and BA 61 highways agencytransport scotland welsh assemBly government llywodraeth cynulliad cymruthe department for regional development northern irelandJune 2010volume 3 SECTION 4 part 16 Bd 61/10registration of amendmentsamend nopage nosignature & date of incorporation of amendmentsamend nopage nosignature & date of incorporation of amendments registration of amendmentsJune 2010volume 3 SECTION 4 part 16 Bd 61/10registration of amendmentsamend nopage nosignature & date of incorporation of amendmentsamend nopage nosignature & date of incorporation of amendments registration of amendmentsvolume 3 highway sructures.

3 Inspection and maintenance SECTION 4 assessmentpart 16Bd 61/10the assessment of composite highway Bridges and structurescontentsChapter1. Introduction 2. assessment of Strength3. Use of Appendix A, BS 5400-5:2005 and BD 16 (DMRB )4. References 5. EnquiriesAppendix A Amendments to BS 5400-5:2005 and Annex A of BD 16 for assessmentAppendix B BD 61/10 The assessment of composite highway Bridges and Structures in English DBFO Schemesdesign manual for roads and BridgesJune 2010 June 2010volume 3 SECTION 4 part 16 Bd 61/101. This Standard, which replaces BD 16 for assessment purposes, gives requirements and guidance for the assessment of existing composite structures and structural elements.

4 It must be used in conjunction with BD 21, BD 37, BD 86, BD 56, BD 44 and other relevant documents. The revisions in the present Standard mainly concern the changes in the British Standard BS 5400-5:2005 and improvements to existing clauses based on the use of the earlier assessment Appendix A of this Standard contains the relevant assessment clauses and annexes which have been presented in the same format as the design clauses in BS 5400-5:2005. These clauses have been specifically developed to suit assessment conditions and, therefore, must not be used in new design or construction. The commentary is contained alongside the assessment clauses. It contains explanations for the main changes from the design code, BS 5400-5:2005, and gives advice on the interpretation of the assessment requirements.

5 Also included are comments and references which provide additional information, and sometimes assessment criteria, appropriate to special situations. Where such situations arise, any special method of analysis or variation of criteria proposed for an assessment should be agreed with the Technical Approval Authority (TAA). All references to characteristic strength should be to characteristic strength or to worst credible The major changes to the Standard compared to the earlier version are as follows:a) A single BD with mandatory clauses including commentary/guidance replacing the previous BD and BA ) To cover old forms of construction cast iron and wrought iron have been inserted in addition to ) Loading Standards BD 37 and BD 86 have been added since the scope of assessment has ) Clarifications have been made to a number of clauses based on the use of the earlier assessment ) The latest revisions to BS 5400-5 have been included in the This Standard gives requirements for the assessment of existing steel/concrete composite highway bridges and structures on trunk roads and motorways.

6 For use in Northern Ireland, this Standard is applicable to all The construction of highway structures will normally be carried out under contracts incorporating the Specification for highway Works (MCHW 1). In such cases products conforming to equivalent Standards or technical specifications of other states of the European Economic Area and tests undertaken in other states of the European Economic Area will be acceptable in accordance with the terms of the 104 and 105 Series of clauses of that Specification. Any contract not containing these clauses must contain suitable clauses of mutual recognition having the same This Standard must be used forthwith for the assessment of steel/concrete composite highway bridges and structures.

7 The requirements must be applied to assessments already in progress provided that, in the opinion of the Overseeing Organisation, this would not result in significant additional expense or delay. Its application to particular assessments must be confirmed with the Overseeing sections Sections of this document which form part of the Standards of the Overseeing Organisations are highlighted by being contained in boxes. These are the sections with which the Design Organisations must comply or must have agreed a suitable departure from standard with the relevant TAAs. The remainder of the document is commended to Design Organisations for 1 introductionJune 2010volume 3 SECTION 4 part 16 Bd 61/102.

8 assessment of The objective of this Standard is to produce a more realistic assessment of the strength of composite elements than has previously been possible using the requirements of the existing design code. This in part is achieved by taking advantage of the information available to an assessing engineer in respect of the material strength, geometrical properties and imperfections which can only be predicted at the design Many of the criteria given in the design code are based on experimental evidence which in some cases have been either conservatively interpreted for use in design or updated by later evidence allowing a less conservative interpretation. For assessment purposes such criteria have been reviewed and amended where The following assessment criteria differ in some respects from criteria used in design:a) There is relaxation or partial relaxation of some design criteria which are of significance in a minority of ) Measured characteristic strength with modified safety factors may be used in place of design ) Forms of shear connection, strengthening and stiffening, including incidental forms, are taken into account where their presence can be ) It may be appropriate to assess some structures on the basis that composite action exists, even though they were not designed as composite structures.

9 This standard contains certain requirements on partial and combination factors for abnormal vehicles. In assessment for Special Types General Order (STGO) and Special Order (SO) vehicle loading, and associated Type HA or Authorised Weight (AW) vehicle loading, the fl values and combination factors must be in accordance with BD 86. partial safety factor for loads, assessment loads QA* must be obtained by multiplying the nominal loads, Qk by fL, the partial safety factor for loads. The relevant values of fL are given in BD 21, BD 37 and BD 86, as appropriate. The assessment load effects, SA* must be obtained by the relation: SA* = f3 (effects of QA*)where f3 is a factor that takes account of inaccurate assessment of the effects of loading, unforeseen stress distribution in the structure and variations in dimensional accuracy in construction.

10 F3 must be taken as for the ultimate limit state and for the serviceability limit state. When measurements have been taken to verify the dimensional accuracy and the measured stresses closely resemble the load effects f3 may be reduced to at the ultimate limit state with the agreement of the TAA. partial safety factor for materials, An important feature of the design code is the application of the partial safety factor for material strength, m, to the characteristic values. In assessment , a reduced value of m may be used as an alternative based on the results of laboratory tests. limit Although BD 21 (DMRB ) specifies that assessments must be carried out at the ultimate limit state, this Standard requires that serviceability limit state checks need to be carried out in a number of cases.