DMRB VOLUME 1 SECTION 3 PART 8 - Standards …

1 August 2001 DESIGN MANUAL FOR ROADS AND BRIDGESVOLUME 1 HIGHWAY STRUCTURES:APPROVAL PROCEDURESAND GENERAL DESIGNSECTION 3 GENERAL DESIGNPA RT 8BA 57/01 DESIGN FOR DURABILITYSUMMARYThe existing Standard and Advice Note (BD 57 andBA 57) have been updated to include:a)Lifting of the moratorium on internal groutedpost-tensioned construction (excluding internalgrouted post-tensioned segmental structures).b)Improvements to durability that can be made bythe use of controlled permeability formwork,dense near surface concrete, corrosion inhibitorsand other materials such as lightweight aggregateconcrete, and stainless steel )To include references to thaumasite )To rationalise references and FOR USEThis revised Advice Note is to be incorporated in document supersedes BA 57/95, which isnow BA 57/95, which is superseded byBA 57/01, and archive as BA 57/01 in VOLUME 1, SECTION 3, part this sheet as : A quarterly index with a full set of VolumeContents Pages is available separately from TheStationery Office Ltd.

2 BA 57/01 Design for DurabilitySummary:The existing Standard and Advice Note (BD 57 and BA 57) have been updatedto include:a) Lifting of the moratorium on internal grouted post-tensioned construction(excluding internal grouted post-tensioned segmental structures).b) Improvements to durability that can be made by the use of controlledpermeability formwork, dense near surface concrete, corrosion inhibitorsand other materials such as lightweight aggregate concrete, and stainlesssteel ) To include references to thaumasite sulfate ) To rationalise references and MANUAL FOR ROADS AND BRIDGESTHE HIGHWAYS AGENCYSCOTTISH EXECUTIVE DEVELOPMENT DEPARTMENTTHE NATIONAL ASSEMBLY FOR WALESCYNULLIAD CENEDLAETHOL CYMRUTHE DEPARTMENT FOR REGIONAL DEVELOPMENTNORTHERN IRELANDV olume 1 SECTION 3 part 8 BA 57/01 August 2001 REGISTRATION OF AMENDMENTSA mendPage NoSignature & Date ofAmendPage NoSignature & Date ofNoincorporation ofNoincorporation ofamendmentsamendmentsRegistration of AmendmentsVolume 1 SECTION 3 part 8 BA 57/01 August 2001 REGISTRATION OF AMENDMENTSA mendPage NoSignature & Date ofAmendPage NoSignature & Date ofNoincorporation ofNoincorporation ofamendmentsamendmentsRegistration of AmendmentsVOLUME 1

3 HIGHWAY STRUCTURES:APPROVAL PROCEDURESAND GENERAL DESIGNSECTION 3 GENERAL DESIGNPA RT 8BA 57/01 DESIGN FOR Affecting Durability - The Conceptual Durability - Problem Durability - Detailed Requirements - Steel MANUAL FOR ROADS AND BRIDGESA ugust 2001 VOLUME 1 SECTION 3 part 8 BA 57/01 August 20011/1 Chapter 1 Introduction1. from the inspection and maintenanceprogramme of highway structures has highlighteddurability problems even where materials, specificationand construction practices have been satisfactory. Theseproblems can often be linked to a design philosophy inwhich minimising the initial cost was consideration may have been given to thelong-term performance of the structure either in thechoice of structural form or in the design ofconstruction details.

4 This has, in too many cases,resulted in maintenance problems requiring costlyrepair. Consequently the Overseeing Organisations arekeen to promote the concept of design for durability,thereby shifting the emphasis to a lowest whole life costdesign from the assessment and strengtheningprogramme has shown that some structures particularlydating from the 1960s and 1970s were substandard. Inmany cases the assessed capacity was not compromisedby any deterioration in condition, but was mainlyinfluenced by the introduction of more onerous designrequirements in the period since their considerations of future changes to designstandards are outside the scope of this Advice Note, andare matters for evaluation as part of the design processand technical approval existing Standard and Advice Note (BD 57 andBA 57) published in 1995 have been updated toinclude:a)Lifting of the moratorium on internal groutedpost-tensioned construction (except for segmentalconstruction).

5 B)Improvements to durability that can be made bythe appropriate use of controlled permeabilityformwork, dense near surface concrete, corrosioninhibitors and other materials such as lightweightaggregate concrete and stainless steel )To include references to thaumasite )To rationalise references and of Serviceability, is the ability of structures to fulfil,without restriction, all the needs which they aredesigned to satisfy. In the design of a highway structure,these needs include:i)the ability to carry without restriction all normaltraffic permitted to use the structure;ii)maintenance of user safety by provision ofadequate containment, separation of classes ofusers, effective evacuation of surface water etc;iii)maintenance of user comfort by avoidingexcessive deflections, vibrations, uneven runningsurfaces etc;iv)avoidance of public concern caused by excessivedeflections, vibrations, cracking of structuralelements etc.

6 V)maintenance of acceptable appearance byavoiding unsightly cracking, staining, the design of structures, however, the first ofthe above needs is supplemented by a separate check onthe maximum load carrying capacity, known as theultimate limit state. The ability to carry abnormalvehicles is also a need which the OverseeingOrganisations new structures must satisfy, but theoccurrence of such loading is deemed to be infrequentand not relevant to the maintenance of the structure is the ability of materials or structuresto resist, for a certain period of time and with regularmaintenance, all the effects to which they are subjected,so that no significant change occurs in theirserviceability.

7 In the design of highway structures thetarget period during which structures must remaindurable, corresponds to the design life as defined inBS 5400: part is influenced by the following factors:i)design and detailing;ii)specification of materials used in construction;iii)quality of 1 SECTION 3 part 8 BA 57/01 August 20011/2 Chapter control of items (ii) and (iii) is achievedthrough the use of accepted Standards and the design of structures is not so readilyassociated with the achievement of durability, beyondsuch considerations as cover to reinforcement, crackwidth limitation or minimum steel plate lack of attention to the durability aspect of designhas resulted in a premature loss of serviceability inmany highway of Advice objective of this Advice Note is to improvethe durability of highway structures by drawing to theattention of designers aspects of design which arerelevant to the durability of structures, but not coveredadequately in the existing requirements for the designof these advice contained in this document.

8 Whichelaborates and supplements the requirements of BD 57( dmrb ), covers areas of design and detailingwhich are relevant to design for durability. The AdviceNote considers various ways in which the design cancontribute to the durability of a structure and identifiesaspects of structural form and detail which requirespecial attention. Many items covered in this documentare acknowledged by designers as being good practicebut their use has not been as widespread as would bedesirable. Certain aspects of inspection, maintenance,specification of materials and construction practicesrelating to durability, which are dealt with in moredetail in the Specification for Highway Works(MCHW 1) and the Notes for Guidance (MCHW 2), arealso briefly main points of this Document concerningimproved durability are included in BD 57 ( ).

9 It should be emphasised that this Advice Note isnot comprehensive and designers should use theirjudgement and experience to ensure that durabilityaspects are catered for adequately in new figures incorporated in this Advice Note areonly indicative. Designers should satisfy themselves asto the suitability of the suggested details to Advice Note is to be implementedforthwith for all schemes currently being preparedprovided that, in the opinion of the OverseeingOrganisation, this would not result in significantadditional expense or delay progress. Designorganisations should confirm its application toparticular schemes with the Overseeing 1 SECTION 3 part 8 BA 57/01 August 20012/1 Chapter 2 Factors Affecting Durability2.

10 FACTORS AFFECTING survey of 200 highway concrete bridges,commissioned by the Department of Transport, TheMaunsell Report (reference 1), identified a number offactors which contributed to the inadequate durabilityof many of the Department s structures. Most of themwere in areas where amendments to existingspecification requirements, or to inspection andmaintenance procedures, should provide improveddurability of structures in the future. The mostimportant of these are briefly discussed , there are a number of important aspectsrelating to durability which need to be addressed byimprovements in conceptual design or in designdetailing; these topics are often not adequately dealtwith in BS 5400, and are discussed further in , Joints and far the most serious source of damage is saltywater leaking through joints in the deck or serviceducts, and poor, faulty or badly maintained drainagesystems.