Investigation on main dynamic characteristics of base-isolated structures under ambient excitation

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Journal of Vibration and Shock ›› 2011, Vol. 30 ›› Issue (11) : 266-271.

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Investigation on main dynamic characteristics of base-isolated structures under ambient excitation

Han Jian-ping 1, 2; Wang Hong-tao 1; Liu Yun-shuai 1, 2; Du Yong-feng 1, 2; Li Hui 1, 2

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Abstract

Ambient vibration tests were conducted on the two base-isolated buildings. Modal frequencies，mode shapes and modal damping ratios were identified using Stochastic Subspace Identification (SSI) and Rational Fraction Polynomial (RFP) methods. The identified results show that under ambient excitation, fundamental frequency of these two base-isolated structures is much larger than the value under frequently occurred earthquake level. And the equivalent viscous damping ratio is as low as the value of non-isolated structure, so base-isolated structures can be considered as the classical proportional damping system under ambient excitation. Furthermore, taking one of the two buildings as case study, identified modal parameters were used as the updating benchmark and the actual equivalent horizontal stiffness of isolation layer was inversed using the multi-objective optimization method. The results show that the actual stiffness value is 10.9 times of that in the design case under frequently occurred earthquake level. Finally, preliminary finite element model were updated based on the inversed stiffness of the isolation layer and the updated model was analyzed numerically. Comparison of the results between analysis and test indicates that the updated model can represent the dynamic characteristics of the base-isolated structure under ambient excitation more reliably.

Key words

based-isolated building / dynamic characteristics / ambient excitation / modal parameter identification / multi-objective optimization / finite element model updating

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Han Jian-ping;;Wang Hong-tao;Liu Yun-shuai;;Du Yong-feng;;Li Hui;. Investigation on main dynamic characteristics of base-isolated structures under ambient excitation[J]. Journal of Vibration and Shock, 2011, 30(11): 266-271