In recent years, seismic isolation buildings are becoming taller and the shape has become more diversified. Therefore, the tensile strain of laminated rubber bearing (LRB) is important. A method of defining the tensile limit of LRB by tensile strain has been proposed, and it is necessary to correctly evaluate the tensile strain generated in LRB due to horizontal and vertical earthquake motions. To evaluate the tensile strain occurring in LRB, it is desirable to perform a time history analysis in which horizontal and vertical are input simultaneously. However, the tensile strain of LRB is affected significantly by the damping setting of the building and the nonlinear characteristics of LRB. Therefore, a detailed examination is required. We propose the estimation method of tensile strain for LRBs using the superposition of horizontal and vertical response values considering that the tensile elastic modulus of LRBs is lower than its compression modulus. In addition, we propose the estimation method of bending moment for a foundation beam when the LRBs are pulled out. The validity of the proposed methods is demonstrated by comparing them with the time-history analysis results using a 24-story isolated base building model.
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