Response of a tension leg platform to stochastic wave forces

Abstract

The equations of motion and the response of a Tension Leg Platform with a single tendon undergoing planar motion are presented. The hull is represented by a rigid cylindrical body and the tendon as a nonlinear elastic beam. Tendons have often been modeled as massless springs, which neglects contribution to the response by the wave forces on the tendons and its varying stiffness due to changes in its tension. The structure is subjected to random wave loading. Linear wave theory is applied and the random wave height power spectrum is transformed into a time history using Borgman's method. The surge and pitch responses for the hull, and the surge response along the tendon are presented for two cases. Case 1 represents a tendon with a hull mass two orders of magnitude smaller than the tendon's mass. In Case 2, the hull mass is two orders of magnitude greater than the tendon. Inclusion of tendon forces were found to significantly increase the amplitude of the surge response for Case 1 but not for Case 2.