Nonlinear Dynamic Analysis of Guyed Tower Platforms

A method of analysis is presented to predict the nonlinear dynamic behavior of compliant offshore structures, in particular guyed tower platforms. The structural model is analyzed in time domain using the normal mode superposition approach. Nonlinearities due to fluid-structure interaction are considered. The nonlinear stiffness of the mooring system is included by suitable modification of the forcing function. Secondary overturning effects due to large deflection are introduced by equivalent lateral forces at each mass point. In analogy to the treatment of the nonlinear mooring stiffness, the nonlinearity of the soil-pile foundation can be accounted for by applying external forces and moments. By way of example, the results of dynamic analyses performed on a guyed tower designed for the North Sea are included.