Fatigue analysis of offshore platforms subject to sea wave loadings

The fatigue damage calculation for random loading on offshore platforms takes the form of a rainflow analysis of the dynamic response of individual members to various sea states. This procedure is lengthu and consequently this paper attempts to provide a theoretical method for determining random load fatigue damage. This dynamic response for many joints leads to a broad band random loading but despite this, previous theoretical methods have simplified the loading to narrow band. This has not been done in the present case; instead, an analysis based on broad band random loading has been produced. This theoretical approach gives a fatigue life estimate which is slightly (6.6%) more conservative, for a typical example, than a rainflow analysis.