The coupled response of a tension leg platform (TLP) for random waves characterized by a long crested sea spectrum is investigated. The response analysis is based on simulation technique which duly considers various nonlinear effects such as relative velocity squared drag force, variable added mass due to variable submergence and nonlinearity due to large excursion. It also accounts for variable tension in tethers due to variable submergence, variable buoyancy and vertical wave forces. Variable tether tension tends to produce sub-harmonic resonance which is critically examined. Also, the phenomenon of super-harmonic resonance which is introduced by variable submergence effect is investigated. The responses are obtained by employing a time integration scheme in which iterations are required at each time station due to nonlinear coupling of all six degrees of freedom. A detailed parametric study is reported that includes maximum, minimum, mean and standard deviation of responses in all six degrees of freedom. Some typical power spectral density functions of responses are shown to illustrate the effects of sub-harmonic and super-harmonic resonances in the system. Copyright (C) 1996 Elsevier Science Ltd
