Experimental study on the dynamic characteristics of the pile group foundation of a base-isolated structure on variable stiffness groud

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Journal of Vibration and Shock ›› 2024, Vol. 43 ›› Issue (2) : 208-218.

YU Xu1,SHAN Zhicheng2,ZHUANG Haiyang3,CHEN Guoxing2

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Abstract

By controlling the intensity and duration of input ground motions, this paper proposes a shaking table test method for pile foundation isolated structure on a variable-stiffness foundation. On this basis, combined with the completed shaking table model tests of isolated structures on different foundations, the influence of the foundation stiffness change on the dynamic characteristics of the pile group foundation of the isolated structure is also analyzed. The results show that the relative stiffness ratio of structure to soil and the strength of the input ground motion significantly affect the moment response of the pile group foundation of the isolated structure. With the increase of the relative stiffness ratio of structure to soil under strong earthquake motion, the upper moment response amplitudes of the middle piles in the pile group foundation of isolated structure grow remarkably, while the lower moment amplitude of the middle pile is relatively small. When the peak acceleration of the input motion and the relative stiffness ratio of structure to soil are greater than a certain limit, the seismic settlement of the pile group foundation increases significantly, and the rotation response of the pile group foundation cap is strong. Meanwhile, the horizontal displacement of grouped pile foundation pile top appears obvious unilateral cumulative horizontal displacement after the main earthquake. It indicates that the pile top of the pile group foundation of the isolated structure tends to occur earthquake damage during the process of foundation stiffness change, while the joint action of the seismic settlement of the pile group foundation and strong rotation reaction of foundation cap may be the main reason for the sharp increase of the pile upper bending moment.

Key words

Variable stiffness foundation / Pile group foundation / Base-isolated structure / Shaking table test / Earthquake response

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YU Xu1,SHAN Zhicheng2,ZHUANG Haiyang3,CHEN Guoxing2. Experimental study on the dynamic characteristics of the pile group foundation of a base-isolated structure on variable stiffness groud [J]. Journal of Vibration and Shock, 2024, 43(2): 208-218

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