Bending stiffness reducer for brace to hull connection

Abstract

Semi-submersibles are subjected to loading from waves, causing racking, longitudinal shear and parallelogramming, or differential movement of the pontoons. The cyclic wave loading makes the various connections, where stress concentrations occur, susceptible to fatigue damage throughout the hull structure. This is most evident at the connections between the braces and the main hull structure. A revised brace to main hull connection with reduced bending stiffness is employed to reduce the moment being transferred from the brace to the hull, thereby reducing the bending stress and susceptibility to fatigue damage. This improved connection employs an internal member to transfer the loads between the brace and hull structure mainly as tension and compression. As a consequence of the improved fatigue performance, the structural weight of the connection can be greatly reduced, thus increasing the capacity with which the semi-submersible hull can operate.