Improved numerical analysis for ultimate behavior of elastomeric seismic isolation bearings

Abstract

Summary Elastomeric isolation bearings consist of multiple rubber layers with their top and bottom surfaces bonded to steel plates to restrict compressive deformation. Deformation constraints result in a variation of elastic modulus over the cross section of the rubber layers. In this paper, we describe a normalized compression modulus distribution on a circular rubber pad. The compressive and bending moduli of the rubber pad can be reproduced by applying the distribution to a series of axial springs. We also present a mechanical model for predicting the behavior of elastomeric seismic isolation bearings subject to large shear deformation and high compressive load. The mechanical model consists of a series of multiple shear springs at midheight and a series of axial springs at the top and bottom interfaces of the bearing. Simulation analyses of bearing tests were conducted to validate the proposed model. The analyses demonstrated that a model for circular lead‐rubber bearings can successfully capture the influence of the axial load magnitude on the bearing shear behavior. The new model can simulate much more realistic behavior than prior models based on a uniform modulus assumption.

Identification and Calibration of Advanced Hysteresis Models for Recycled Rubber–Fiber-Reinforced Bearings

“…In the present study, the Axial SP material, available in OpenSees, was associated with the vertical behavior in tension and compression. The material is completely defined by the following parameters: (i) initial elastic stiffness along vertical direction E init , (ii) post-elastic stiffness in compression (1/2 E init ) and in tension (1/100 E init ), (iii) cavitation stress (f ty = 2 G r [6]) and (iv) yielding stress in compression (f cy = 100 MPa [16]).…”

Evaluating Collapse Fragility Curves for Existing Buildings Retrofitted Using Seismic Isolation

“…All that considered, in the present paper, the mechanical model of the HDRBs has been improved to overcome those limitations. In particular, the Kikuchi bearing element [16] has been adopted in lieu of the HDR bearing model. The Kikuchi bearing element is a two node link element with multi-spring mechanical model which includes two sets of multiple axial springs (one on the top and the other at the bottom of the bearing height) and a set of mid-height multiple (radial) shear springs, all bound together by rigid links.…”

A Resilience and Robustness Oriented Design of Base-Isolated Structures: The New Camerino University Research Center

“…In particular, linear springs representing the HDR bearings have been replaced by non-linear elements adopting the HDR isolator (Masaki et al, 2017) available in the Sap 2000 software (Computer and Structures, 1995). This model is bidirectional and accounts for non-linear phenomena, such as the strain-dependent behavior of the HDR bearings, but neglects other aspects, such as the strain hardening at large shear strains (larger than 250%) or the effect of the vertical load on the horizontal response of the bearings (Ishii and Kikuchi, 2018). This may be important for large axial loads close to the buckling capacity of the bearing in the deformed configuration (Kelly, 1997).…”