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Calculating allowable stress for cyclic loaded structures


Frequently Asked Questions

In the UK, you should consult BS7608:1993 'Code of practice for fatigue design and assessment of steel structures' which provides guidance on allowable cyclic stresses for welded joints. Similar rules will be found in BS8118 Part 1 1991 'Structural use of aluminium - Code of practice for design' for joints in aluminium alloys. The allowable stress is strongly dependent on joint geometry; for example, fillet welds have a lower fatigue strength than butt welds. The standards provide a series of sketches of typical joints showing potential failure sites, and give the fatigue performance for each in terms of an S-N curve (where S is the allowable nominal cyclic stress range and N is the fatigue design life in cycles). Similar data are published by other national standards organisations.

See also 'Fatigue Strength of Welded Structures', by S J Maddox, 2nd Edition, Abington Publishing, 1991. (ISBN 1 85573 013 8)

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