Integrity of an Offshore Structure Subjected to Waves: a Stochastic Analysis

Abstract

A fatigue analysis procedure was developed to evaluate the structural integrity of a drilling tower welded to an offshore platform. The tower is built from welded steel plates and it has uncertainties on the thickness of the plates and on the welds. The weld between the tower and the offshore platform is critical for fatigue and the knowledge of the probability distribution of the stress cycles on this critical point of the structure is necessary to estimate its fatigue life. The stresses on this point are given by the dynamics of the tower and the excitation of the tower is given by the dynamics of the platform (base excitation) which in turn is given by the wave loads.