Performance of steel-laminated rubber bearings subjected to combinations of axial loads and shear strains

摘要

Bridge isolation is a common means for mitigating the actions of structures subjected to earthquake excitations, thermal effects, creep and shrinkage. Steel-laminated rubber bearings are common devices that are being used widely in seismically isolated structures. Current code requirements for steel-laminated rubber bearings differ significantly with regard to requirements relevant to tensile stresses that are developed within the elastomer. Additionally, there is an acknowledged gap regarding the understanding of the response of bearings when subjected to combined and/or fluctuating axial loads (compressive or tensile) shearing and rotations due to imposed earthquake excitations, both causing local and/or global tension and/or buckling. The latter are influenced significantly by the shape factor and the behaviour of the steel reinforcements. In this framework, an extensive numerical study was conducted to examine the development of stresses within the elastomer of bearings and the response of the steel reinforcements. In particular, combination of variable axial displacements ranging from 4% compression up to 90% tension, shear strains up to 210 percent and rotations up to 0.0205 rad, were imposed on the bearings, causing tensile stresses within the elastomer and yielding of the steel plating (reinforcements). These loads were imposed in the form of displacement time histories corresponding to the response of bearings on a seismically excited bridge that was analysed previously, as well as the bridge bearings which were used for this research f 1]. The finite element software ABAQUS was used for the numerical analyses.