Fatigue under Wide Band Random Stresses

A method for predicting high cycle fatigue under stationary gaussian wide band stress processes is developed. The rainflow cycle counting method is used as the basis for predicting fatigue damage. Stress simulations from various spectral density models were analyzed using the rainflow method. Statistical analysis of these results provided a closed form expression for fatigue damage. A principal application of the method is to predict fatigue in the welded joints of offshore structures, an example of which is provided. A long term nonstationary sea state is modelled as a sequence of stationary sea states. Thus the example also illustrates how fatigue under certain types of nonstationary stress processes can be analyzed.