Shaking table tests for structures with viscous dampers considering SSI effect

In order to investigate influences of soil-structure interaction (SSI) on aseismic effect of viscous dampers in structures, shaking table tests for a steel frame energy-dissipating structure model with viscous dampers on rigid and pile group foundations were conducted. The similarity relationship between the original structure and the tested model was determined according to the dimensional analysis. The soil used in tests was silty clay and a laminar shear type soil box was adopted to reduce the boundary effect. The super-structure of the model was a 5-storey steel frame structure, its energy-dissipating elements were viscous dampers. The data of structural dynamic characteristics, floor accelerations and displacements of the model with and without viscous dampers under different seismic excitations and different base conditions were obtained with shaking table tests. For the pile group supported model, strains of plies and contact pressures of soil-pile interfaces were measured. The results indicated that for structures without viscous dampers, the damping ratio of the structure system has a considerable increase due to SSI effect; however, for structures with viscous dampers, SSI effect has little influence on the damping ratio of the structure system; SSI effect has a significant influence on floor acceleration responses, SSI effect reduces the seismic responses of the super-structure of the model, the larger the seismic inputs, the greater the SSI effect, the aseismic efficiency of dampers for pile group foundations has a bigger decline compared with that for rigid foundations; for structures on a pile group base, the viscous dampers can not only reduce seismic responses of the super structure, but also reduce those of the base, the safety of both the super structure and the base is improved.