Enhancing the performance capabilities of seismically isolated buildings using multi-stage friction pendulum sliding bearings

摘要

One concern in the design of seismically isolated structures is the selection of bearing properties so that optimal performance is achieved over a range of excitations and performance metrics.For example,to withstand very severe near-fault motions,isolation bearings frequently become so large,stiff and strong that they provide little isolation during moderate or severe events.Experimental and numerical investigations are presented to characterize isolation bearings capable of progressively exhibiting different hysteretic properties at different stages of response and the feasibility of targeting these properties to achieve specific performance goals for a range of ground motion intensities and structural dynamic characteristics.A newly developed triple pendulum isolator incorporates four concave surfaces and three independent pendulum mechanisms.Pendulum stages can be set to address specific response criteria for moderate,severe and very severe events.This paper presents shaking table test results for a 1/4-scale seismic isolated steel braced frame.Three earthquake records were considered,and for each record,different hazard levels and components of excitation were applied.The test results confirm the beneficial effects of having isolator properties progressively change with displacement amplitude.Nonlinear dynamic analyses of the test specimen and more realistic building systems are also presented.