Response of a High Damping Rubber Bearing to Multiaxial Excitation

A high damping rubber bearing fabricated as part of a seismic isolation system was tested at the Caltrans Seismic Response Modification Device Test Facility at the University of California, San Diego. The purpose of the test program, which consisted of 33 tests, was to assess the impact of multiaxial excitation and input rate on the response of the bearing. The test protocol consisted of unique tests, including testing the bearing in all six degrees of freedom (uncoupled and coupled) and testing the bearing dynamically to failure. This article examines the hysteretic response and resulting performance parameters of the bearing to the different tests. The most notable impacts on the bearing's hysteretic response were the axial loading and coupling the lateral degrees of freedom, while the rotational degrees of freedom had minimal impact on the bearing's response. The bearing's hysteretic response to coupling input in the rotational degrees of freedom with lateral and axial degrees of freedom was consistent with the expected performance from superimposing the response to input from individual degrees of freedom. The bearing failed at almost three times the design shear strain and at a shear force over five times the shear force at the design shear strain during the dynamic test to failure.