Experimental and numerical studies of the dynamic coupling effect in the primary-secondary system

Many complicated dynamic coupling effects(DCE) exist in the primary-secondary system(PS system) under earthquakes, among which the dynamic interaction and tuning effect have a more significant influence. However, the existing numerical analysis methods and experimental works are mostly based on the assumption of a small mass ratio, resulting in no significant interactions within the coupled system to be discussed. Therefore, a series of dynamic characteristics tests and shaking table tests were conducted to determine the working of the DCE works on the PS systems with appropriate mass ratios, and test results were used for the validation of an analysis method without the mass limitation and for the extended numerical analyses. According to the results, the dynamic interaction could reduce the responses of the secondary system(S system), and the reduction was positively related to the mass ratio, the tuning effect could cause a divergence of the natural frequencies and about 10-40% decrease in the primary system(P system) response and approximately 7-34 times increase in the S system response. The results of the extended analysis demonstrate the effectiveness of increasing the damping of connection, and decoupled analysis will yield more than double the security redundancy.