Finite-Element and Experimental Investigation of the Post-Buckling Stability of an Elastomeric Seismic Isolation Bearing

An important consideration for the design of seismic isolation systems composed of elastomeric bearings is the safety of individual bearings for maximum considered earthquake shaking. One assessment of bearing safety requires the bearing be stable at the maximum displacement. Although there exists no codified procedure for assessing stability in the laterally deformed configuration most engineers use the overlapping area method whereby the critical load capacity at zero lateral displacement is reduced by the ratio of the overlapping area between the top and bottom bearing end plates to the total bonded rubber area. This paper presents the results of a finite-element and experimental investigation aimed at improving the understanding of the stability of elastomeric bearing in the deformed configuration. The results of detailed nonlinear FE analysis and experimental testing of an elastomeric bearing with shape factor equal to 10 suggest the overlapping area method is overly conservative in predicting the critical load capacity in the deformed configuration.