Seismic Response Control Of Eccentric Structures Using Tuned Liquid Dampers

From theoretical analysis and seismic disasters, it can be concluded that the seismic response is not only in translational direction, but also in torsional direction. There are two reasons that are responsible for the torsional response of structures. First, there exists torsional component for the motion of ground or phase delay for the different sites of ground under earthquake. Second, structures exist eccentricity for the inconsistency between the center of mass and stiffness. The torsional component can aggravate the destroy of structures especially for the eccentric structures. So, the control problem of eccentric structures under earthquake is very important The thesis focus on the seismic response control of eccentric structures using tuned liquid dampers and the main contents are summarized as follow:(1) The parameters of Circular Tuned Liquid Column Dampers (CTLCD) are analyzed. The motion of equation for CTLCD is established and the nonlinear damping of CTLCD is equivalently linearized. The optimal parameters of CTLCD under purely torsional condition are studied and the equation of the optimal frequency ratio and damping ratio are derived. The expression of equivalent damping ratio for purely torsional vibration and torsionally coupled vibration is acquired. The effects of parameters of controlled system on the equivalent damping are analyzed. The results show that CTLCD is an effective control device on torsional response.(2) The control method for eccentric buildings using TLCD and CTLCD under seismic is presented. The expression of stochastic response of torsionally coupled system is derived. The optimization method for the parameters of liquid dampers is given based on Genetic Algorithm. The results show that the liquid dampers with optimal parameters can effectively reduce the translational and torsional response of eccentric buildings if the objective function of optimization is selected to consider each degree of freedom.(3) A 8-story eccentric steel building, with two TLCDs on the orthogonal direction and one CTLCD on the mass center of the top story, is analyzed. The optimal parameters of liquid dampers are optimized by Genetic Algorithm. The structural response with and without liquid dampers under bi-directional earthquakes are calculated. The results show that the torsionally coupled response of structures can be effectively suppressed by liquid dampers with optimal parameters.(4) The shake table test was carried to verify the control effect of liquid dampers to eccentric buildings. A steel model of building with eccentricity only in one direction was designed. One TLCD and CTLCD were placed on the top story of experimental model. The building mode with and without liquid dampers were experimented on the shake table. The experimental results show that the liquid dampers can effectively suppress the torsionally coupled response of eccentric buildings.(5) The beat phenomenon for the vibration control using CTLCD is studied. The undamped control system, linearly damped structure with undamped CTLCD and damped control system, are analyzed respectively to understand the beat phenomenon from a mathematical point of view. The results show that the beat phenomenon on the free vibration of structure can be disappeared for CTLCD with higher damping. The transient response of the structure can not be degraded promptly when beat phenomenon appears, so there would be large errors if only consider the stead response of structure.(6) A novel control law for semi-active tuned liquid dampers, market-based control (MBC) is presented. The equation of motion for structure-TLCD control system is established the MBC semi-active control strategy is illustrated. The results indicate that MBC semi-active TLCD control method facilitates reducing structural vibration with a lower energy expenditure and the control effect is better than passive TLCD.(7) To improve the performance of passive adjustable frequency TLCD, Semi-active Variable Stiffness Tuned Liquid Column Damper (SAVS-TLCD) is presented, with the stiffness of additional spring online adjustable. The state of stiffness can be ON or OFF according to the requirements of control system during the vibration. The results indicate that SAVS-TLCD has larger frequency width of reduction and can still be effectiveness if there is a little error between the frequency of TLCD and the structure.