An Experimental Study Of Tuned Liquid Dampers And The Control Of Mistuned Effects

A tuned liquid damper(TLD)can be made of a fire tank on the roof,with the advantages of low cost,small space,easy maintenance,no complex mechanical structure,no fatigue problems and can be effective in small vibration amplitude,is an effective solution to the wind vibration comfort of high-rise buildings.However,there are still key technical problems in engineering applications which restrict its wide application and development,including the lack of concise and accurate design model and the mistuned effect caused by water level deviation or earthquake damage of the main structure.To solve the problems,a large scale TLD shaking table test was conducted to obtain the dynamics characteristics of a TLD,and an equivalent model of TLD considering the nonlinearity of frequency and damping is proposed.A passive liquid replenishment system to reduce the water level deviation and a water depth control strategy with lower water depth control standard deviation requirement are proposed.A probabilistic statistical method is used to evaluate the negative effect of the mistuned TLD due to the plastic damage of main structure under earthquake.The maximum response amplification coefficient due to the mistuned is provided.The main results are as follows:(1)A shaking table tests of a TLD was conducted with a large-sized water tank.The real-time dynamic wave height was captured based on dynamic recognition technology.The full-time reaction force,wave height,and damping ratio of TLD were obtained under different excitation loads,flow-damping devices and water depth conditions for large-scale TLD.The nonlinear frequency and damping ratio of TLD under these different conditions were obtained.(2)A new nonlinear stiffness and damping model based on equivalent wave height(NSD-h)for TLD was proposed with the principle of equal potential energy.The equations for frequency correction coefficient,and damping ratio which are related to dimensionless relative wave height,are given.The deviations of the prediction of time history peak value and root mean square value of TLD under wind and earthquake loads by the new NSD-h model and the original NSD model are compared with experimental results.Under wind load,the accuracy of the NSD-h model is significantly higher than that of the NSD model,while under earthquake conditions,the NSD-h model is slightly better than the NSD model.The equivalent linearization equation of stiffness and damping obtained from the NSD-h model showed good agreement with experimental results under harmonic and wind load.(3)The frequency response function of a tuned damper is presented.The effects of factors such as mass ratio,damping ratio,and stiffness ratio of the tuned damper on the fundamental frequency and vibration reduction efficiency of the main structure are studied and verified in a practical engineering structure.The effect of the tuned damper on the fundamental frequency of the main structure was verified based on the frequency response function.The impact of increasing mass ratio and damping ratio on the vibration reduction efficiency was also studied when there is a frequency deviation of TLD.(4)A passive water replenishment system for maintaining the water level stability of the TLD(TLD-SRS)is proposed.The water depth stability in the TLD was achieved,by adding a sub-tank which is far away from the frequency of main structure.Based on experimental results,the TLD-SRS system is proved to significantly improve the stability of water depth control during the sloshing process.Based on the experimental data analysis,the TLD-SRS system can reduce the water level overshoot(the percentage of tank water level over the target level)in the tank from 17%(using the common float replenishment device)to no more than2%,and the reduction of the acceleration RMS rises from 10～22% to 14～33%.(5)The vibration reduction efficiency distribution of the double water tank TLD under different water depth was studied,based on an actual structure.By the assumption of normal distribution,a water depth control strategy with lower water level standard deviation control requirements under the same guarantee rate is proposed.The water level control strategy in which the water level is lower than the target and higher than the other one,is prove to be effective in reducing the requirement of the water level.The standard deviation of the water level increases from 2.5% to 10% at the same guarantee rate of 95% and minimum vibration reduction rate of-5%,which greatly reducing the difficulty of water level control.(6)An assessment of the maximum negative effect on structural response is conducted considering the frequency deviation of the tuned dampers due to the plastic damage of the main structure under seismic conditions.Based on the responses of plastic model under 183 natural wave of earthquakes,the negative response dynamic amplification coefficients of the top displacement of the main structure and the dynamic effect of the tuned dampers were proposed under a 99% guarantee rate under medium and large earthquakes.The maximum dynamic amplification coefficient of the structure is 1.02-1.04 and that of the tuned dampers is 3.78.