Factors Affecting the Dependency of Shear Strain of LRB and SHDR: Experimental Study

Chao-Yong Shen,Yang-Yang Chen,Yu-Hong Ma,Xiang-Yun Huang

doi:10.3390/act10050098

Abstract

In this research we conducted a sensitivity experimental study where we explored the dependency of the shear strain on the seismic properties of bearings, namely lead rubber bearing (LRB) and super high damping rubber bearing (SHDR). The factors studied were vertical pressure, temperature, shear modulus of the inner rubber (G value), loading frequency, and loading sequence. Six specimens were adopted, i.e., three LRBs and three SHDR bearings. A series of test plans were designed. The seismic characteristics of the bearings were captured through a cyclic loading test, which included post-yield stiffness, characteristic strength, area of a single cycle of the hysteretic loop, equivalent stiffness, and equivalent damping ratio. A whole analysis of variances was then conducted. At the same time, to explore certain phenomena caused by the factors, an extended discussion was carried out. Test results showed that the temperature is the most dominant feature, whereas the G value is the least contributing factor, with the effect of the loading frequency and the loading sequence found between these two. The increment of the post-yielded stiffness for LRB from 100% to 25% is a significant reduction from a low temperature to high one. The slope of the characteristic strength versus the shear strain for LRB under high temperature is larger than the one under low temperature.

Highlights

By lengthening the natural period of an isolation structure and dissipating the earthquake energy, the earthquake action of the isolation structure can be reduced considerably [1]
Elastomeric bearings are mostly applied in this technology, which includes linear natural rubber bearing (LNR), lead rubber bearing (LRB), elastic sliding bearing (ESB), and high damping rubber bearing (HDR)
There is little damping for LNR, which is a bearing constructed of alternating elastomeric layers bonded to intermediate steel plates; here, the elastomeric rubber is natural

Summary

Introduction

By lengthening the natural period of an isolation structure and dissipating the earthquake energy, the earthquake action of the isolation structure can be reduced considerably [1] At present, this innovative technology is used widely in buildings and bridges, and it has successfully withstood many real earthquakes [2,3]. Elastomeric bearings are mostly applied in this technology, which includes linear natural rubber bearing (LNR), lead rubber bearing (LRB), elastic sliding bearing (ESB), and high damping rubber bearing (HDR). In LNR, the natural rubber is added into a special material, such as active carbon; after it is vulcanized under high temperature, dissipative damping can be provided after the shear deformation of bearing takes place, where LNR becomes HDR. Investigations about the horizontal mechanical properties of elastomeric bearings by testing were carried out, and some useful numerical models were put forward

Methods

Results

Conclusion