Coupling behavior of shear deformation and end rotation of elastomeric seismic isolation bearings

Abstract

Summary This paper presents a mechanical model for predicting the behavior of elastomeric seismic isolation bearings subject to combined end rotations and shear deformation. The mechanical model consists of a series of axial springs at the top, mid‐height and bottom of the bearing to vertically reproduce asymmetric bending moment distribution in the bearings. The model can take into account end rotations of the bearing, and the overall rotational stiffness includes the effect of the variation of vertical load on the bearing and the imposed shear deformation. Static bending tests under various combinations of vertical load and shear deformation were performed to identify the mechanical characteristics of bearings. The test results indicate that bearing rotational stiffness increases with increasing vertical load but decreases with increasing shear deformation. Simulation analyses were conducted to validate the new mechanical model. The results of analyses using the new model show very good agreement with experimental observations. A series of seismic response analyses were performed to demonstrate the dynamic behavior of top‐of‐column isolated structures, a configuration where the end rotations of isolation bearings are typically expected to be larger. The results suggest that the end rotations of elastomeric bearings used in practical top‐of‐column isolated structures do not reduce the stability limit of isolation system. Copyright © 2016 John Wiley & Sons, Ltd.

Assessing the significance of nonlinear rotational behavior in high damping rubber bearings for seismic performance of base‐isolated RC frame building

“…The material nonlinearity of high damping rubber further emphasizes the need to reconsider using a constant modulus in derivation to ensure accurate outcomes. However, it is noteworthy that for lower‐damping rubber bearings, the results obtained by Equations () and () align well with the experiment findings presented in 31 . Meanwhile, in square bearings, the results derived using similar equations also exhibit consistency with the test results 29 .…”

“…However, it is noteworthy that for lower-damping rubber bearings, the results obtained by Equations ( 7) and ( 14) align well with the experiment findings presented in. 31 Meanwhile, in square bearings, the results derived using similar equations also exhibit consistency with the test results. 29 Therefore, in order to capture the nonlinear effects of the rotational behavior of high damping rubber bearings on the seismic response of the isolation system, the rotational spring stiffness of the BIL model is determined based on initial stiffness derived from experimental results in subsequent time-history analysis.…”

“…For most seismic isolated buildings, the rotational behavior of bearings is often neglected or simplified as elastic in numerical analyses 15,29 . However, previous studies have demonstrated that the rotational behavior of bearings is nonlinear 31,36,37 . In this study, two models are considered: the BIL model, which represents the rotational springs (flexural springs and torsional spring) of the bearing as linear, and the BINL model, which considers the rotational springs as nonlinear.…”

“…15,29 However, previous studies have demonstrated that the rotational behavior of bearings is nonlinear. 31,36,37 In this study, two models are considered: the BIL model, which represents the rotational springs (flexural springs and torsional spring) of the bearing as linear, and the BINL model, which considers the rotational springs as nonlinear. The BIL and BINL models differ only in the representation of the rotational springs, while the mechanical behavior of the shear and vertical springs remains the same.…”

“…Their findings demonstrated that end rotation significantly affects the horizontal stiffness, lateral displacement, bending moment, and shear force of the laminated rubber bearings. Ishii et al 31 introduced a novel mechanical model for elastomeric bearings subjected to combined end rotations and shear deformation. This model was validated through static bending tests, and a series of seismic analyses were conducted on top-of-column isolated structures.…”