Large-scale shaking table test on tall buildings with viscous dampers considering pile-soil-structure interaction

A series of large-scale shaking table tests of tall buildings with nonlinear viscous dampers on soft soils in pile group foundations are performed to better understand the effect of the seismic pile-soil-structure interaction (PSSI) on the dynamic responses of the pile, soil, structure and the performance of the viscous dampers. Two different models are investigated, including a fixed-base structure with viscous dampers, representing the situation ignoring the soil-structure interaction (SSI) and a structure with viscous dampers supported by 3-by-3 pile group foundation in soft soil within a shear laminar soil container. The superstructure is a 12-story reinforced concrete (RC) frame. The seismic excitations of Shanghai Bedrock waves, 1995 Kobe earthquake and 1999 Chi-Chi earthquake events are selected and used in the shaking table tests. Finally, a three-dimensional numerical model is developed and verified to be appropriate for capturing the dynamic responses of soil-pile-structure with viscous dampers. Based on the experimental results, the PSSI system has longer natural periods and the frequencies decrease more lightly than the fixed-base structure after the tests. In addition, the influences of PSSI on the frequencies are much greater than the damping ratio. Moreover, by comparing with the fixed-base conditions, PSSI tends to decrease elastic-plastic inter-story drift of the structure more greatly than the acceleration and shear force. However, the overall deformation of the structure may increase due to the obvious and large rocking and translational components. More interestingly, the hysteretic performance and the efficiency of viscous dampers on mitigating the structural dynamic responses are reduced by the PSSI effect compared with the fixed-base models. Consequently, ignoring the SSI effects may result in unrealistic results of the seismic responses of the superstructure and overstate the performance of the nonlinear viscous dampers. It is of great importance to consider the seismic SSI effect in the design of viscous dampers and structures.