Effect of supplemental damping on seismic response of base isolated frames under near & far field accelerations

摘要

The seismic isolation, as a passive control method of structures and an innovative approach in resistant seismic design, significantly reduces the response of structural systems induced by strong ground motions. The performance of these systems in Near Fault (NF) ground motions with large pulses is different from that of Far Fault (FF) ground motions. It is indicated that the effects of near field earthquake with large velocity pulses can bring the seismic isolation devices to critical working conditions. To overcome this problem, the application of viscous damper is represented as an approach to improve the performance of these systems in near field earthquakes. In the present paper, through modeling six base isolated structures, the seismic responses were studied under near field and far field earthquakes. Nonlinear time history analyses were performed, applying the finite element software of ABAQUS to study the influence of various values of supplemental damping (5% similar to 40%) on the responses of base isolated structures. The results demonstrated that, generally, by increasing supplemental damping ratio under near field earthquakes, the base displacement decreases; however, the stories relative displacements and accelerations increase. It is observed that by increasing supplemental damping ratio under far field earthquakes, the base displacement and the stories relative displacements decreases; however, the stories accelerations increase. Based on the analyses, these variations proved to be more prevalent under near field earthquakes and taller structures.