Passive Devices for Wave Induced Vibration Control in O shore Steel Jacket Platforms

Performances of tuned mass dampers and friction dampers to mitigate the wave induced vibrations in jacket type o shore platforms have been compared in this study. Due to the random nature of ocean waves, a full stochastic analysis method has been used to evaluate the response of the structures equipped with these devices. A stochastic linearization technique has been used to take the nonlinear behavior of friction dampers into account. The developed mathematical formulation has been applied to evaluate the response of realistic models, and to nd out the optimal values for the adjustable parameters of friction dampers. The results have been veri ed in comparison with time domain nonlinear analyses results. Also, a computer utility has been provided in FORTRAN to perform the spectral fatigue analysis of platforms and together with a Genetic Algorithm utility, it has been used to nd out the optimal parameters of a tuned mass damper to dissipate the wave induced vibrations of the platforms. Although the eciency of both dissipative systems increases for more exible platforms due to the dominancy of the dynamic response, the functionality of TMD devices is more dependent on the dynamic characteristics of the platform; friction dampers seem to be more ecient for xed steel jacket platforms.