AN INTEGRATED DYNAMIC ANALYSIS APPROACH FOR OFFSHORE FATIGUE DAMAGE PREDICTION AND STRUCTURAL MEMBER DESIGN

The use of a full dynamic analysis in the frequency domain, employing a modal superposition method with a pseudo-static correction technique, is applied to the structural design of offshore platforms. It is shown that it is possible to adopt a unified analysis strategy for design purposes, which has the advantage of avoiding the need for several different model discretisations with distinct mesh refinements. For structural systems subjected to time-varying loads, such as offshore structures, fatigue analysis must be performed using a complete three-dimensional model discretisation in order to obtain true stress-time histories for each joint. It is shown that a phase difference between member forces significantly affects the results for checking for member failure and joint capacity, so that it is necessary to adopt a detailed structural model such as is used for fatigue analysis.