Application of Shape Memory Alloy Tuned Mass Damper in Vibration Control of Jacket type Offshore Structures

The effort has been made in this research to reduce the vibrations of the jacket platforms vibrated by irregular waves through dynamic vibration absorbers (DVAs). The production of intelligent materials and their application in the design of control devices have made significant progress in the past two decades. The shape memory alloy (SMA) is an intelligent material highly capable of damping vibrations. Hence, use has been made in this study, of the shape memory alloy tuned mass damper (SMA-TMD) to control the vibrations of the offshore jacket platforms. Here, the equations governing the platform/damper vibrations have been developed by simulating them as a multi-degree of freedom lumped mass system and analyzed by the direct integration method. To evaluate the structural damping force and the SMA hysteretic behavior, the extended Rayleigh damping model and idealized multi-linear constitutive model have been used, respectively. As a case study, a 90 m-high jacket platform (in 80 m-deep water) has been equipped with SMA-TMD and its dynamic responses have been estimated. An average decrease of 16 percent in the root mean square of the deck displacements and 75 percent reduction in the power spectral density function (in the resonance state) are the results of jacket platform equipped with optimized SMA-TMD.