Experimental investigation of cavitation in elastomeric seismic isolation bearings

Design standards for seismic isolation of nuclear power plants in USA will consider the effects of beyond design basis loadings, including extreme earthquakes. Seismic isolation is being considered for new build nuclear power plant construction and design of isolation systems will have to consider these extreme loadings, which includes the possibility of net tensile force in bearings under beyond design basis shaking. A series of experiments were conducted at University at Buffalo to characterize the behavior of elastomeric bearings in tension. Sixteen low damping rubber bearings from two manufacturers, with similar geometric properties but different shear moduli, were tested under various loading conditions to determine factors that affect cavitation in an elastomeric bearing. The effect of cavitation on the shear and axial properties of elastomeric bearings was investigated by performing post-cavitation tests. The test data were used to validate a phenomenological model of an elastomeric bearing in tension, which is implemented in OpenSees, ABAQUS and LS-DYNA.