Frequently Asked Questions
Any type of loading which produces a stress history of a cyclical nature (i.e. with a succession of peaks and troughs) is potentially capable of producing fatigue cracking. Some common sources of cyclic loading, any or all of which may be relevant in particular applications, are:
- fluctuating loads
- acceleration forces in moving structures
- pressure changes
- temperature fluctuations
- mechanical vibrations
- environmental loading (wind, currents and waves, particularly when vortex shedding is induced)
Particular care should be taken to assess dynamic magnification effects when loading frequencies are close to one of the natural frequencies of the component or structure.
It should be noted that cyclic loading from different sources may be significant at different phases of the life of a structure, such as construction, transport, installation and in-service, and they may involve different loading frequencies.
See Clause 1.7 of BS 7608: 1993 Code of Practice for 'Fatigue design and assessment of Steel structures'.
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