Codeofpracticefor
Fatigue design and assessmentofsteel structures
Committeesresponsibleforthis BritishStandard
Standards Policy Committee (WEE/-) to Technical Committee WEE/44 upon The preparation of this British Standard was entrusted by the Weldingwhich the following bodies were represented:
AEA TechnologyAssociation of Consulting EngineersBritish Constructional Steelwork Association Ltd. British Railways BoardDepartment of TransportDepartment of Transport (Transport Research Laboratory)Electricity Association ESDU International Ltd.Federation of Manufacturers of Construction Equipment and CranesInstitution of Structural Engineers Institution of Civil EngineersMinistry of DefenceProcess Plant AssociationRailway Industry Association of Great Britain Society of British Aerospace Companies LimitedUnited Kingdom Offshore Operators AssociationWelding Institute
Amendments issued since publication
Amd. No. Date Comments8337 February 1995 Indicated by a sideline in the margin
BSI 03-1999
The following BSI referencesCommitteereferene WEE/44 relate to the work on this standard:Draft for ment 87/77328 DC
ISBN 0 580 21281 5
Contents
Inside front cover PageCommittees responsible Foreword ivSection 1. General1.1 1.2 Seope References 1 11.3 Definitions 11.4 1.5 Symbols and units Assessment 3 31.6 Design life 31.7 1.8 Basis of fatigue analysis Fatigue loading 3 41.9 Factors on fatigue life 41.10 Features influencing fatigue behaviour 51.11 Fracture mechanics Section 2. Classification of details 52.1 General 92.2 2.3 Classification of details Unclassified details 24 62.4 Workmanship and inspection 24Section 3. Stress calculations 2.5 Welded steel decks 253.1 General 273.2 3.3 Stress range in parent material Stress range for welds 27 273.4 Effective stress range for details in unwelded members in3.5 which the whole or part of the stress is pressive Calculation of stresses 27 273.6 Geometrical stress concentrations 873.7 88 Axial stresses in bolts Stresses in welds attaching shear connectors3.9 Derivation of stress spectra 30Section 4. Allowable fatigue stresses4.1 4.2 S-N curves Tensile stress limitations 31 314.3 Modifications to basic S-N curves Treatment of low stress cycles 31 334.4 4.5 Treatment of high stress cycles 344.6 Joints subjected to single stress range Joints subjected to a stress spectrum 34Annex A (normative) Fatigue design philosophy 4.7 34 46Annex B (normative) Explanatory notes on detail classification 47Annex C (normative) Guidance on the calculation of stress concentration factors 51Annex D (normative) Guidance on the use of fracture mechanics 61define design stresses Annex E (normative) Fatigue testing and the use of test data to 69Annex F (normative) Cycle counting by the reservoir method 71Annex G (informative) Background notes on sources of data
PageFigure 1 - Weld quality category determined by adjacent detail Annex H (informative) Bibliography 80Figure 2 - Reference stress in parent metal 35 36Figure 3 - Reference stress in weld throat 36geometrical discontinuity Figure 4 - Typical example of stress concentrations due to 37geometrical hard spot Figure 5 - Typical example of stress concentration caused by a 38Figure 6 - Stress concentration factors 39Figure 7 - Example of hot spot stresses in a nodal joint Figure 8 - Summary of mean-line S-V curves 40 41Figure 9 - Summary of standard basic design S N curves 42Figure 10 - S /UTS-N curves for bolts with cut or ground or rolled threads under axial loading (class X) 43Figure 11 - Toe grinding to improve fatigue strength 44Figure 12 - Grinding of weld at tubular nodal joint Figure 13- Typical S -V relationship 45 45Figure B.1 - Edge distance 52Figure B.2 - Failure modes at weld ends Figure B.3 - Failure modes in cruciform and T-joints 52 53Figure B.4 - Failure modes in transverse butt welds 53Figure B.5 - T-junction of two flange plates Figure B.6 - Cruciform junction between flange plates 54 53Figure B.7 Alternative method of joining two flange plates 54Figure B.8 - Local grinding adjacent to cope hole in type 7.1 joint Figure B.9 - Use of continuity plating to reduce stress 55concentrations in type 8.1 and 8.2 joints 55Figure B.11 - Single fillet corner weld in bending Figure B.10 - Example of type 8.3 or 8.4 joint 56 56Figure B.12 - Example of a third member slotted through amain member Figure C.1 Types of misalignment and distortion 57 61Figure D.1 - - Flaw dimensions 63Figure D.2 -Transverse load-carrying cruciform joint Figure F.1 - Example of cycle counting by reservoir method 64 70Figure G.1 - Comparison of proposed S-N curves for bolts in axialTable 1 - Classification of details: plain material free from welding loading with curves from ESDU data sheets 79 7Table 2 Classification of details: bolted or rivetted spliced or lappedTable 3 - Classification of details: fasteners and shear connectors connections 8 9Table 4 - Classification of details: continuous welded attachments 10essentially parallel to the direction of applied stress Table 5 - Classification of details: welded attachments on theTable 6 - Classification of details: full penetration butt welds surface or edge of a stressed member 12between co-planar plates 13Table 7 - Classification of details: transverse butt welds in sections and tubes 15
PageTable 8 - Classification of details: load carrying fillet and T-butt joints between plates in different planes 17Table 9 - Classification of details: slotted connections andpenetration through stressed members Table 10 - Classification of details: cireular tubular members 0% 21Table 11 - Classification of details: seam welds 22Table 12 - Classification of details: branch connections Table 13 - Upper limits of flaw area of planar flaws and slaginclusions in transverse butt welds 96Table 15 - Nominal probability factors Table 14 - Details of basic S-N curves 32 33Table D.2-Values of g and f Table D.1 -Values of M M and M 66Table E.1 - Fatigue test factor F 67Table G.1-Sources of the content 72of various types of threaded connection expressed in Table G.2 Experimentally determined fatigue strengthsterms of stress range/UTS List of references Inside back cover 77
