Base isolated/damping platforms for seismic protection of essential equipment - Hinge-Bearing Platform

One isolation platform, consisting of four hinge-bearings supporting one horizontal steel frame that in turn supports a mass that simulates the self-weight of a piece of equipment was tested. Each hinge-bearing consists of an elastomeric bearing atop of a hinge joint. The hinge joint acts as an articulation connecting the elastomeric bearing and load cells that in turn are connected to the shake table. The hinge-bearing isolation system was provided by Seismic Foundation Control Inc. To simulate the equipment weight, steel plates and concrete blocks totaling 72.7 kips are supported by the horizontal frame (8 feet long x 8 feet wide). 5 channel load cells were placed under each isolator to record the axial and shear forces. The test program consists of white noise excitation, single directional and bi-directional sinusoidal excitations and three-directional earthquake ground and floor motions. The floor motions intend to replicate floor accelerations recorded in multi-story buildings under historic earthquake shaking.