ABSTRACT

Elastomeric bearings such as rubber bearings frequently used as isolators for bridges deteriorate gradually when they are exposed to radiation or at elevated temperatures. Meanwhile, elastomeric bearings could be damaged by the failure mechanisms of creep and fatigue when they are subjected to external loads. The dynamic resistance of elastomeric bearings is thus reduced due to the changes of their molecular structure caused by environmental or mechanical attacks. As a result, the damping efficiency of isolators made from elastomeric bearings might be dramatically decreased when they are under a cyclic loading of earthquake. This paper mainly aims at investigating the deterioration of dynamic behavior of rubber bearings under variously environmental attacks such as cyclic loads and elevated temperatures. Effects of fatigue and thermal aging on the dynamic behavior of rubber bearings are discussed and presented.

INTRODUCTION

Fatigue is a typical failure mechanism for rubber bearings when they are subjected to cyclic loads in practical engineering application. The fatigue failure of rubber bearings will be accelerated if their side surfaces are not perfectly bonded or some interior defects pre-exist due to manufacturing. When rubber bearings are under cyclic compression, their side surfaces will expand and the pre-existing defects might propagate after some cycles of loading. As a result, the damping efficiency of rubber bearings used as isolators in bridges or buildings is significantly reduced. Hence, the design goal for rubber bearings to prevent seismic damage will not be achieved. In addition, rubber bearings in service are frequently subjected to various environmental attacks such as elevated temperature, high moisture and radiation. Presumably, the molecular structure of rubbers will be changed, resulting in the deterioration of the mechanical properties and damping efficiency of rubber bearings.

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