Experimental and Analytical Studies on the Horizontal Behavior of Elastomeric Bearings under Support Rotation

Abstract

Laminated elastomeric bearings are used widely as seismic isolation devices. Most previous studies on the horizontal behavior of elastomeric bearings have assumed that the rotations of the top and bottom supports of the bearings are zero, mainly because in conventional practice, the superstructure and substructure above and below the isolation layer have very large rotational stiffness. However, in certain applications, including in bridges, in midstory isolation, and isolation of high-rise buildings, the support surfaces of elastomeric bearings may experience appreciable rotations. The main objective of this study was to investigate the effect of support rotation on the horizontal behavior of elastomeric bearings. For this purpose, an extensive experimental campaign on a circular isolator was conducted. Two experimental procedures were used. The first procedure investigated the behavior of the bearing under lateral quasi-static cyclic displacement, constant axial load, and constant rotation. The cyclic tests illustrated the effects of rotation on the hysteresis loops. The second procedure investigated the behavior of the bearing through monotonic lateral displacement under constant axial load and rotation. The experimental results were used to validate an advanced finite-element model (FEM) of the bearing. In addition, the experimental results were used to validate a mechanical model (MM) proposed by the authors in a previous study to account for the effect of rotation on the lateral behavior of elastomeric bearings.