Critical tension-shear load of elastomeric seismic isolators: An experimental perspective

When the height-width ratio of isolated high-rise building is excessive large, elastomeric isolators may suffer from tension accompanying with large horizontal shear strains under strong earthquake excitations. It may be not safe if only considering isolators suffering from purely tension without considering horizontal shear strain. In order to investigate the critical behavior of isolator under tension-shear load, five linear natural rubber bearings with the same inner structure have been experimentally evaluated at different horizontal strain amplitudes, ranging from zero to 483%, including axial tension and purely shear. At the same time, test results have been compared with the theory results. Test results show that the critical load decreases nonlinearly with the increase of horizontal shear strain, which reveals that it is unreasonable to define the threshold value of tension independent of amount of horizontal shear strain. Comparing with test results of five rubber bearings, the theory results overestimate the ultimate tension strength of elastomeric seismic isolators in most cases. The photos of damage show isolator may occur in different damage pattern at different shear strains, 100% shear strain can be thought as the dividing line. All of the before-mentioned conclusions are drawn by only five isolators, more researches needs to be done in the future.