Optimal design of TMD under long-term nonstationary wave loading

Traditionally, the use of a tuned mass damper (TMD) is to improve the survi ability of the primary structure under extraordinary loading environment wh ile the design loading condition is described by either a harmonic function or a stationary random process that can be fully characterized by a power spectral density (PSD) function. Aiming at prolonging the fatigue life of a n offshore platform, this study considers an optimal design of TMD for the platform under long-term nonstationary loading due to long-term random sea waves characterized by a probabilistic power spectral density (PPSD) functi on In principle, a PPSD could be derived based on numerous ordinary PSD fun ctions; and each of them is treated as realization of the corresponding PPS D. This study provides a theoretical development for the optimal TMD design by minimizing the cost function to be the mean square value of the expecte d long term response. A numerical example is presented to illustrate the de veloped design procedure.