Abstract
The jacket structure is a fixed offshore structure. Its natural frequency of vibration is higher than the peak ocean wave frequency. Generally, the response of the jacket structure platform is significantly small in comparison to other floating offshore structures. But, the small response is good enough to generate significant stress at the joint level of jacket members. This is due to the rigid connection between the members at the joint level. In literature also, it’s well-studied that the joint of the jacket structure is vulnerable to stress developed and shows fatigue damage. Further, a reduction in the response of jacket structure using conventional design procedures may have a huge financial burden. So, dynamic response control of such a structure to reduce the effect of fatigue damage at the joint of members is the most economical and practical approach. In this paper, a tuned liquid column damper (TLCD) is used as a passive control device to control the response of the jacket structure. The control in response is achieved by tuning the TLCD at the natural frequency of the Jacket structure. This gives control only at the natural frequency of the structure, but the response at excitation frequency remains unchanged. This way, the total control achieved is not good enough. Further, TLCD is converted to semi-active TLCD by changing the pressure at the column. The fuzzy control algorithm is used to guide the pressure changes in the TLCD column so that optimum control at the natural frequency of the jacket and excitation frequency can be achieved. Further, the robustness of Semi-active TLCD is also shown based on a change in the nature of excitation.
