FATIGUE DAMAGE ASSESSMENT OF SHIP STRUCTURES BASED ON THE LONG-TERM DISTRIBUTION OF LOCAL STRESSES

Abstract

The paper addresses the evaluation of the fatigue life of ship structures based on a probabilistic approach that considers the stochastic nature of the ocean environmental loading and the service profile of the ship. The method is based on a linear spectral analysis of the stress range response. The local stress range response transfer functions are obtained by using a three-dimensional finite element model. The response process for each short-term sea state is modelled by a Rayleigh distribution. The long-term response period and long-term stress range distribution are then determined and are fitted as a Weibull distribution. The Palmgren-Miner linear cumulative damage model is applied. An example calculation is presented for a tanker and the influence of several scatter diagrams on the fatigue life of structural details is examined.