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In recent years, development of effective devices for seismic energy dissipation in structures has become more important to keep response of structure in elastic range. Dampers are used in structures to reduce response and effect of seismic forces. Also, using secondary mass technology can help seismic energy dissipation. Among these systems one can mention tuned mass damper and tuned liquid column damper, working base on secondary inertia in structures. In this paper, hybrid system of tuned mass & liquid column dampers in series was considered with mass ratios 0.035-0.005, 0.03-0.01 and 0.02-0.02. Time history analysis using the Northridge, Tabas and Loma Prieta earthquakes for 20 story structures were modeled in Simulink Matlab software considering shearing structure and damper modeling in every blocks separately. Effect of damper to structure is determined as forces applying on corresponding story. Performance indices using software outputs such as root mean square and Maximum of displacement and acceleration of stories were calculated. Performance of single and hybrid systems has been compared due to different earthquakes. Also effect of hybrid systems in series was studied by increasing head loss coefficient. Results show that performance of hybrid systems is dependent on earthquake characteristics that improves with increasing secondary mass ratio. For example under the Northridge earthquake, hybrid system in series tuned mass & liquid column damper with mass ratios 0.035-0.005, 0.03-0.01 and 0.02-0.02 decrease root mean square of displacement of stories 45, 27 and 2 percent respectively and also by selecting optimum frequency ratio based on responses of structure. For example maximum acceleration of hybrid system of tuned mass & liquid column damper in series with mass ratio 0.035-0.005 is optimum frequency ratio in 2.9 and also by selecting this frequency ratio decrease maximum acceleration of up and down stories in 20 story structure. By comparing effects of hybrid system Tuned Mass & Liquid Column Damper in series with different mass ratios on two structures with periods of 1.5 and 2.44 second are considering where by increasing stiffness of structure, performance of hybrid system was improved leading to decrease of acceleration responses and reduction of displacement responses. For example, J1 in 20 story structure with period 1.5 second is 0.71 whereas in other structure is 0.79 that show hybrid system has better performance in structure with period 1.5 second. Hybrid system in series damper with mass ratio 0.035-0.005 have best performance to reduce displacement stories of 20 story structure with period 1.5 second as J3=0.56 means decrease 44%. Also in other structure, hybrid system with mass ratio 0.035-0.005 has best performance to reduce displacement at top floor with J4=0.56. Also performance of hybrid system to reduce maximum displacement of stories was improved by increasing head loss coefficient in tuned liquid column damper

Keywords: Hybrid system in series Tuned Mass & Liquid Column Damper, passive control, Optimum Frequency Ratio

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