Publishing and copyright information

The BSI copyright notice displayed in this document indicates when the document was last issued.

The following BSI references relate to the work on this document:

Committee reference WEE/37
Drafts for comment 13/30102062 DC; 15/30329661 DC

Publication history

First edition April 1993
Second (present) edition March 2014

Foreword

Publishing information

This British Standard is published by BSI Standards Limited, under licence from The British Standards Institution, and came into effect on 31 March 2014. It was prepared by Technical Committee WEE/37, Acceptance levels for flaws in welds. A list of organizations represented on this committee can be obtained on request to its secretary.

Supersession

BS 7608:2014+A1:2015 supersedes BS 7608:2014, which is withdrawn.

Information about this document

Guidance on general fatigue design philosophy is given in Annex A, which also contains a brief description of the method of using this British Standard. A more general method for assessing welded joints using the hot-spot stress, only included previously for assessing tubular joints, is also included.

The relevant application standard or specification for the particular product being assessed specifies the following:

the loading to be assumed for design purposes, including its magnitude and frequency;
the required life of the structure;
the environmental conditions;
the required nominal probability of failure.

BS 7608:2014 was a full revision of the standard, and introduced the following principal changes [1]:

Introduction of the hot-spot stress method with guidance on finite element stress analysis (FEA).
New correction for both plate thickness and applied bending with allowance for welded joint proportions.
Additional weld details; some have been reclassified.
Weld quality requirements based on fitness for purpose.
Revised sea water corrosion fatigue data.
New rules for bolts.
Design data to resist shear fatigue failure.
Guidance on stress calculation for combined loading.
Revised cumulative damage rules.
Comprehensive guidance on use of weld toe improvement methods.
New guidance on acceptance fatigue testing and statistical analysis of results.

European standards containing fatigue rules for steel structures and pressure vessels have been published since the 1993 edition of this British Standard. It is therefore not applicable to product areas covered by them. It is applicable to a wide range of other steel product areas that do not have specific fatigue rules.

Text introduced or altered by Amendment No. 1 is indicated in the text by tags . Minor editorial changes are not tagged. The principal changes are to Table 4 to Table 10, Clause 14, Clause 16, Table 18, new Table 21, Annex C and Annex F.

Use of this document

As a guide, this British Standard takes the form of guidance and recommendations. It should not be quoted as if it were a specification or a code of practice and claims of compliance cannot be made to it.

Presentational conventions

The guidance in this standard is presented in roman (i.e. upright) type. Any recommendations are expressed in sentences in which the principal auxiliary verb is “should”.

Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element.

Contractual and legal considerations

This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

1 Scope

1.1 General

This British Standard gives methods for assessing the fatigue life of parts of steel products that are subject to repeated fluctuations of stress. It is applicable to all areas of industrial application that are not covered by other British Standards containing fatigue assessment rules.

NOTE Some British Standards have specific product acceptance tests for fatigue life, but do not have assessment rules. In such cases the guidance in this British Standard might be applicable for product development purposes.

1.2 Applications not covered

This British Standard is not applicable to the following application areas;

lighting columns (see BS EN 40);
concrete building and civil engineering structures (see BS EN 1992);
steel building and civil engineering structures [see BS EN 1993 (all parts)];
composite steel and concrete building and civil engineering structures [see BS EN 1994 (all parts)];
unfired pressure vessels (see BS EN 13445); and
fixed offshore structures (see BS EN ISO 19902).

1.3 Materials

This British Standard covers:

wrought steel material products;
welds in fully machined areas of steel casting;
ferritic alloy and low alloy steels;
austenitic and duplex stainless steels;
unprotected weathering steels; and
threaded fasteners.

It is applicable to yield strengths in the range 200 N/mm² to 960 N/mm² and ultimate tensile strengths in the range 360 to 1 200 N/mm² for material thicknesses 3 mm and greater.

This British Standard is not applicable to the following:

proprietary fasteners;
steel castings;
cold drawn products;
wire ropes; and
steel for reinforcement in concrete.

1.4 Manufacturing processes

This British Standard is applicable to machined products with the following exceptions:

rough sawn surfaces;
surfaces requiring high quality surface finish (e.g. lapping, polishing, honing, fine grinding); and
machined details with sharp corners (e.g. key ways, un-radiused shoulders).

The following manufacturing processes are also covered:

cold formed wrought products;
weld toe improvement methods;
arc welded joints, with the exclusion of joints between rectangular and square hollow sections;
in-line butt welds made by power beam or friction welding;
tensioned and un-tensioned bolted joints and hot-driven riveted lap joints loaded in shear; and
thermal cutting.

This British Standard is not applicable to the following manufacturing processes:

resistance welding processes and brazing;
contact joints under pressure where fretting occurs;
adhesively bonded joints;
shearing and punching; and
surface hardening.

1.5 Environment

The fatigue design data in this British Standard are applicable to internal and external air environments. They are applicable to structural steel products exposed to sea water.

They are not applicable to unprotected stainless or weathering steel products in sea water or aggressive corroding environments (e.g. chloride, sulphide, strong acid or alkali).

The data are applicable to products operating at temperatures below the creep range of the steel.

This British Standard is not applicable to products operating in the creep regime.

2 Normative references

3 Terms and definitions

4 Symbols and units

5 Fatigue assessment procedure

6 Design life

7 Fatigue loading

8 Environmental considerations

9 Factors on fatigue life

10 Features influencing fatigue behaviour

11 Fracture mechanics

12 Classification of details

12.1 General

12.2 Classification of details

13 Unclassified details

13.1 General

13.2 Post-welding treatments

14 Workmanship and Inspection

14.1 General

14.2 Quality aspects detrimental to fatigue

14.3 Control of quality for fatigue

15 Stress calculations

15.1 General

15.2 Stress range in parent material

15.3 Stress range in fillet welds

15.4 Effective stress range for details in unwelded members in which the whole or part of the stress is compressive

15.5 Calculation of stresses

15.6 Calculation of nominal stresses

15.7 Calculation of hot-spot stresses

15.8 Axial stresses in bolts

15.9 Derivation of stress spectrum

16 Allowable fatigue stresses

16.1 Tensile stress limitations

16.2 S-N curves

16.3 Modifications to basic S-N curves

16.4 Treatment of low stress cycles

16.5 Treatment of high stress cycles

16.6 Joints subjected to a single stress range

16.7 Joints subjected to a stress spectrum

Bibliography

BS 7608:2014+A1:2015

Guide to fatigue design and assessment of steel products

Current, Under Review

Published:

31 Mar 2014