Stochastic response of compliant platforms to irregular waves

Response of a compliant platform to irregular waves is determined using finite element method. The tower is idealized by 2-D beam elements with an elastic support at the guy lines location. The flexural characteristics of the beam correspond to the four corner members of the trusses. The guying system is modelled by an axial element with linear load deformation characteristics. A computer program based on the linearized Morison's equation and the linear (Airy) wave theory, is developed to calculate the total force based on the storm wave height data at different levels of the structure. The response of the structure to random waves is based on the spectral approach. The direct and cross spectral densities of the generalized wave forces are determined and used to obtain the spectral densities of the generalized modal coordinates and mean square response at each level. Possible extension of the method is indicated to compute the evolutionary response to nonstationary wave forces.