Evaluation of Design Equations for Critical Properties of Reinforced Elastomeric Bearings and Recommended Revisions

Abstract

Global interest in seismic isolation technology continues to increase due to the satisfactory performance of isolated structures in recent earthquake events. In addition to the overall response of the structure, the design of the isolation devices is an important consideration. Reinforced elastomeric bearings are commonly used in seismic isolation applications and as bridge bearings. Relevant standards have been developed to guide designers on several critical design properties, such as the compression and bending modulus and the maximum shear strain due to compression and rotation. These standards commonly assume that the elastomer is incompressible and that the reinforcement is rigid and inextensible. In this paper, inconsistencies in design equations within and between selected standards are identified and discussed. It is shown that the aforementioned assumptions can result in significant error depending on the design and geometry of the bearing. To address these inconsistencies and to minimize the error, new design equations are derived and proposed. The proposed design equations include the compressibility of the elastomer and the extensibility of the reinforcement. The derivation of the proposed design equations is presented and the equations are compared against the analytical solutions and current design standards. It is shown that the proposed design equations are accurate, simple to use, and can address current inconsistencies in critical design properties.