Dynamic soil-structure interaction of a shallow founded shear frame and a frame equipped with viscous dampers under seismic loading

Abstract

It is not uncommon for buildings requiring good seismic performance, with objectives of immediate occupancy and continuous operation, to be equipped with supplemental damping devices. Oil dampers are a popular type of velocity-dependant devices that can be fitted into a structure without incurring considerable changes to the frame stiffness. Seminal experimental work into the seismic performance of structures with viscous dampers is based primarily on large-scale testing of prototype frames fixed to rigid shaking tables overlooking ground flexibility effects. Most literature examining the effects of soil-structure interaction (SSI) on the behaviour of structures with viscous dampers use highly idealised representations of the foundation-soil system stiffness and damping characteristics. This paper utilises high gravity dynamic centrifuge testing to investigate the effects of different base fixity conditions on the seismic behaviour of two model shear structures; one fitted with miniature oil dampers and one left bare for comparison. The base fixity conditions replicated are full base fixity and shallow embedment into dry, dense and loose sand. Experimental results indicate that the damped frame is less responsive to changes in ground compliance relative to its bare frame counterpart. Any apparent drop in damper control with reduced base fixity is driven by improvements in the seismic performance of the bare frame benchmark rather than an increase in the dynamic response of the damped structure. Despite the adverse effects of reduced base fixity on the energy dissipated by the dampers, SSI did not negatively affect the performance of the damped frame.