Generation and application of a standardised load-time history to critical ship structural details

Marine structures always experience variable amplitude loading during their service periods. The fatigue crack growth behaviour of marine structures and materials has been proved from laboratory tests to be sensitive to the loading sequence encountered. In order to take account of the load sequence effect, fatigue life prediction should be based on fatigue crack propagation theory rather than the currently used cumulative fatigue damage theory. A unified fatigue life prediction method for marine structures has been developed in the authors' group. In order to apply the unified fatigue life prediction method for newly designed structures, authorities such as the classification societies should provide a standardised load-time history such as the TWIST and FALSTAFF sequences for transport and fighter aircraft. This paper is mainly aimed to propose a procedure how to generate the standardised load-time history for marine structures based on a short-term load measurement and how to use the resulting standardised load-time history to a critical ship structural detail based on the unified fatigue life prediction method.