Tension Buckling in Multilayer Elastomeric Bearings

The compression buckling of mutilayer elastomeric bearings which are widely used as vibration mounts, bridge bearings, and seismic isolators for buildings is well understood and is governed by theoretical analysis and confirmed by extensive experimental work. What is not well known is that the theoretical analysis that predicts the compression buckling behavior also predicts that a bearing could be subject to buckling in tension with a tension buckling load that is of the same order as the compressive buckling load and a buckled shape that is the same as that in compression. The tensile buckling load will not be achievable in practice in most bearings since it will generally be much larger than the load that will induce cavitation in the elastomer, but the analysis can be very valuable in explaining the behavior of seismic isolators when loaded in tension while laterally displaced. This can occur when extreme seismic loading on an isolated building induces global overturning. Isolators at the periphery of the building can be in a state of combined tension and shear. The analysis shows that the elastomer can sustain the tension load without cavitation since rotation of the central portion converts tension to rotated shear.