Multiaxial behaviors of laminated rubber bearings and their modeling. I: Experimental study

Cyclic behaviors of three types of laminated rubber bearings under multiaxial loading state are studied. First, the characteristics of the restoring forces of these bearings in small amplitude are investigated. The experimental results show that the equivalent stiffness of high damping rubber bearings is increased and the damping ratio is decreased as the increase of the amplitude. In addition, the restoring force of a lead rubber bearing is found to highly depend on the vertical load. Second, a triaxial loading experiment, in which two-directional displacement paths are given to the bearings under a constant vertical load, is conducted. The experimental results indicate that horizontal restoring forces possess the coupling effects. The equivalent stiffness and damping ratio of high damping rubber bearings and natural rubber bearings are increased due to this coupling effect in comparison with the biaxial loading case, while the lead rubber bearing shows a slight decrease in them. Hence it is understood that the effects of the triaxial loading are not negligible and these have to be considered in a rational and reliable design.