Influence of nonlinear fluid viscous dampers in controlling the seismic response of the base-isolated buildings

Abstract

Recently, many buildings have originally been designed as base-isolated to mitigate the structural vibration. However, buildings with base isolation systems can undergo displacement/amplification demand due to the inherent nonlinear behaviour of the base isolators, especially in earthquake-prone regions. Hence, in some cases it could be necessary to control the seismic response of the base-isolated buildings using supplemental damping device. This paper investigated the effectiveness of nonlinear fluid viscous damper (NFVD) considering design parameters for the base-isolated buildings with lead rubber bearing (LRB). For this, 10-storey benchmark steel moment resisting frame isolated with LRB having a series of isolation periods (T) of 3, 3.5, 4, and 5 s was used. These base-isolated frames consist of three bays and NFVDs having different damping exponents (α) of 0.15, 0.30, 0.50, and 0.70 were inserted in the mid, corner, and all bays of each base-isolated frame at the ground level. The case studied frames were modelled with a finite element program in which LRB elements were characterized by bi-linear hysteretic behaviour while NFVD elements were represented considering the Maxwell model having an elastic spring and a viscous dashpot in series. The nonlinear response of the frames with LRB and NFVD were evaluated by the nonlinear time history analyses using five ground motion records. The analysis of the results were comparatively evaluated considering certain engineering demand parameters such as the storey, bearing, and relative displacements, roof and inter-storey drift ratios, absolute acceleration, base shear, base moment, input energy, and hysteretic curves. One of the main findings of this study is that the base-isolated building with the passive damping device as control attenuation satisfactorily responded when associated with appropriated design parameters.