Investigation of Fatigue Damage for Stiffened Plates in Splash Zone for a Semi-Submersible

Fatigue damage at side structures are widely reported for ships because the external wave pressure reaches maximum at still-water level. At the same time, the ship side structures also withstand noticeable hull girder loads (vertical and horizontal bending moments). Correct assessment of the fatigue damage due to global and local load effects is of vital importance for side structures of marine vessels. Little research, however, has been carried out for the side structures of semi-submersibles. Like ships, the semi-submersible side structures experience both global and local load effects. Especially for external pressure, the effect of intermittent wet and dry surfaces on the side shell near or above the waterline needs to be considered. In this paper, a global analysis model of the Gjøa semi-submersible, shown in Figure 1, is built and the local response for the side structure is investigated. The contribution of fatigue damage due to global and local load effects are compared and presented.