Vibration Control Of An Offshore Platform Based On Variable Stiffness Tuned Mass Damper

The purpose of this thesis is to investigate the control effect of a semi-active vibration absorber developed for an offshore platform and a vibration control system is also designed. The vibration of the structure is suppressed by installing the new and innovative variable stiffness tuned mass damper (VSTMD) on the top deck of the platform. Under the irregular wave force, the deviation of the acceleration response of the top deck motion is used as the cost function to optimize the parameters of the control device. Tuned to the optimum parameters, the VSTMD reduces the top deck acceleration by 21% averagely. To make the control system feasible and easy to operate, a new scheme is put forward. The acceleration information of the top deck motion is used as input data and an empirical formula is used to obtain the optimum parameters of the VSTMD. The analysis demonstrates that under the sea condition measured in Mexico Gulf in 1996, the deck acceleration deviation can be reduced by 20 % averagely compared with that of without VSTMD. The result indicates that VSTMD can provide a reliable and inexpensive means to mitigate the vibration of the offshore structures. The realization of this scheme not only can improve the working and living condition on the platform but also can prolong its operational life span. This is bond to bring huge economic profit to offshore engineering, so it has a promising future. To validate the effectiveness of this vibration control method experimentally, a real control system is made to control the vibration of an oil platform model under simulated wave loadings and the experiment will be conducted in the next term.