Implications of Tendon Modeling on Nonlinear Response of TLP

Abstract

This paper studies the implication of the tendon modeling on the global response of tension leg platforms (TLPs) in general, and on the surge motion (low-frequency response) and the limits of the tendon forces (high-frequency response) in particular. The tendons are modeled as massless elastic springs connected to the hull or as flexural beam elements with mass and hydrodynamic forces. For the latter, a complete nonlinear large-displacement coupled analysis is performed. The TLP studied is subjected to regular waves with various heights and periods in different water depths. Among other conclusions, the results show that while the simple elastic spring modeling of the tendons with constant lateral stiffness is satisfactory in computing the surge response (horizontal motion) amplitude, the hydrodynamic forces on the tendons are very important in accurately predicting the surge mean value (offset). The hull setdown (vertical displacement associated with the horizontal motion) also significantly affects the tendon forces, particularly for not very deep water.