Tension buckling in multilayer elastomeric isolation bearings

Seismic isolators are constructed from multiple layers of elastomer (usually natural rubber) reinforced with steel plates; they are, therefore, very stiff in the vertical direction, but soft in the horizontal direction. The buckling of these bearings under compression load is a well-understood phenomenon and has been widely studied. It is therefore unexpected that the buckling analysis for compression predicts that the isolator can buckle in tension at a load close to that for buckling in compression. The linear elastic model that leads to both compression and tension buckling is an extremely simple one, so it might be argued that the tensile buckling may be an artifact of the model itself rather than a property of the isolator. To test the simple theoretical model we have conducted a numerical simulation study using a finite element model of a multilayer elastomeric bearing. We find that the prediction of tensile buckling by the simple linear elastic theory is indeed accurate and not an artifact of the model.