A Three-Dimensional Multi-Spring Model for Square Lead-Rubber Bearings Under Large Shear Deformations

Abstract

The paper describes a new analytical model for predicting the large displacement behavior of square lead-rubber isolation bearings. The present model is developed by extending to three dimensions an existing model for elastomeric isolation bearings under severe axial loads and shear deformations. Static loading tests of square lead-rubber bearings are performed to investigate the effect of loading direction on bearing behavior. The test results showed that the ultimate behavior is strongly influenced by loading direction, especially for large shear deformation and high axial load. The results of analyses using the new model show very good agreement with the experimental results. Keywords : Seismic isolation, Lead-rubber bearing, Large deformation, Axial force, Non-linear hysteresis model

Three‐dimensional analysis for square seismic isolation bearings under large shear deformations and high axial loads

“…The values of these parameters are established using bi‐linear model design equations. Detailed descriptions of the evaluation of these parameters are available in 5, 6, 11.…”

“…Ryan and Chopra have proposed an analytical model for lead–rubber bearings by modifying the two‐spring model with a bi‐linear hysteretic relationship and an empirical equation for bearing yield strength 4. Two of the authors also have proposed an analytical model for elastomeric isolation bearings under large shear deformations, through the introduction ofnonlinear hysteresis relationships to the two‐spring model 5. There remains, however, a problem that cannot be solved even by these various improved two‐spring models.…”

A mechanical model for elastomeric seismic isolation bearings including the influence of axial load

“…The uncoupled model consists of uncoupled shear and axial springs and does not include any interaction between the horizontal and vertical forces. The second is the nonlinear Koh-Kelly model, which was previously proposed by the authors [8]. The nonlinear Koh-Kelly model is the Koh-Kelly model with the enhancement of nonlinear shear and rotational springs and includes the effect of interaction between horizontal and vertical forces.…”

“…The overall stiffness matrix for an elastomeric bearing, K ab , is obtained by arranging the elements of the partial stiffness matrices, K am , K nb , and K mn (Equations (6), (8), and (20)), into a 10×10 165 matrix:…”