Tuned liquid column damper (TLCD) has been used extensively to improve the seismic behavior of structures, and different methods have been proposed for optimal design of TLCDs on linear structures. For improving the effectiveness of TLCDs, multiple tuned liquid column dampers (MTLCDs) have been proposed, and each TLCD has different dynamic parameters. In this paper designing optimal MTLCDs and assessment of its effectiveness in mitigating the response of structures under earthquake excitations have been studied. The parameters of TLCDs have been determined based on minimizing the maximum displacement of structure through solving an optimization problem. Genetic algorithm (GA) has been used for solving the optimization problem. For illustration, the method has been used for designing optimal MTLCDs for a ten-storey linear shear frame subjected to a white noise excitation. According to the results of numerical simulations it could be said that the proposed method for designing optimal MTLCDs has been effective regarding the simplicity and convergence behavior of the method. Based on designing MTLCDs for different values of MTLCDs total mass ratio, it has been concluded that MTLCDs total mass affects significantly the performance of MTMDs where its increasing has led to improve MTLCDs performance. Also, testing the optimal MTLCDs structure under different testing excitations has shown that the performance of MTLCDs depends on the characteristics of earthquakes. 1. Introduction During past decades different structural control systems including passive, active, semiactive, and hybrid control mechanisms have been proposed to protect the structures under environmental loads such as wind and earthquake loads [1]. Extensive researches have been conducted theoretically and experimentally to study the efficiency of the proposed control systems whose results show that each of control systems has its individual benefits and limitations regarding the practical and economical issues. In the passive control systems area, it has been found that these kinds of mechanisms are simple and attractive in practical applications. Hence, different mechanisms such as mass damper [2], multiple tuned mass dampers [3–5] viscoelastic dampers [6, 7], tuned liquid dampers, and tuned liquid column dampers [8] have been proposed in this area. The efficiency of single TLCD in improving the response of structures under wind and earthquake loads has been studied in some researches. Sakai et al. [8] proposed tuned liquid column damper to mitigate excessive vibrations as a passive control
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