Experimental simulation of base-isolated buildings pounding against moat wall and effects on superstructure response

摘要

Base-isolated buildings are typically important facilities expected to remain functional after a major earthquake. However, their behavior under extreme ground shaking is not well understood. A series of earthquake simulator experiments were performed to assess performance limit states of seismically isolated buildings under strong ground motions, including pounding against a moat wall. The test setup consists of a quarter scale three-story frame isolated at the base with friction pendulum bearings and a moat wall model. An effort was made to properly scale the strength and the stiffness of the frame relative to the bearings properties from a professionally designed isolated three-story steel intermediate moment-resisting frame so that realistic yielding mechanisms can be observed. The moat wall was modeled as either a rigid triangle steel stopper or a concrete wall of various thicknesses with soil backfill. The moat wall gap was set to various displacement increments to examine the sensitivity of this parameter and also to assess the effects of impact on the superstructure at different velocities. The test results indicate that the contact forces are largely dependent on the gap distance, impact velocity and wall flexibility and, in extreme cases, pounding can induce yielding in the superstructure.