Tests of reduced-scale seismic isolation bearings for the U.S. Advanced Liquid Metal Reactor (ALMR) program

This paper summarizes a portion of a thorough series of tests on several different designs of reduced-scale high damping rubber isolators for the U.S. Advanced Liquid Metal Reactor (ALMR) program. A formal procurement specification has been developed by the program participants for purchasing bearings of several different scale factors and designs. The reduced-scale bearings in the specification have geometric scale factors of 1/4 and 1/8 so that dynamic tests can be performed at realistic rates, The 1/8-scale bearings also have a range of rubber layer thicknesses so that the effects of shape factor on mechanical properties may be determined. Tests of bearings from two suppliers using one of the 1/8-scale bearing designs are summarized here. The test program includes horizontal shear tests to moderate and high shear strains at a range of axial loads and frequencies, as well as vertical tests and failure tests to quantify the margin of safety in the actual design. Load-History effects including short-term stiffness reduction and long-term stiffness recovery are also under study. The primary focus of these tests is on characterizing the behavior of the compounds proposed by the bearing suppliers.