ABSTRACT

In this paper, the control performance of Circular Tuned Liquid Column Dampers (CTLCD) to torsional response of offshore platform structure excited by ground motions is investigated. Based on the equation of motion for the CTLCD-structure system, the optimal control parameters of dampers are given through some derivations supposing the ground motion is stochastic process. The influence of systematic parameters on the equivalent damping ratio of the structures is analyzed with purely torsional vibration and translational-torsional coupled vibration, respectively. The results show that CTLCD is an effective torsional response control device.

INTRODUCTION

The resource in land is almost extinct and the exploitation of resource in sea is becoming more and more important with the development of human society. The offshore platforms, served as the base of sea work, should be safe and comfortable enough to guarantee the production and life of workers. However, most offshore platforms are located in seismic regions and the platforms are easily to be seriously damaged by earthquakes. Hence, It is necessary to research into the seismic response and vibration control of offshore platforms.

Tuned liquid column damper (TLCD) as a passive control device can suppress the structural vibration by the motion of liquid in a column container. The potential advantages of liquid vibration absorbers include: low manufacturing and installation costs; the ability of the absorbers to be incorporated during the design stage of a structure, or to be retrofitted to serve a remedial role; relatively low maintenance requirements; and the availability of the liquid to be used for emergency purposes, or for the everyday function of the structure if fresh water is used. TLCD is an effective control device developed from Tuned Liquid Dampers (TLD), which increases structural damping through the vibration of liquid in the U-shaped container to suppress the structural dynamical response.

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