Evaluation of Elastomeric Bearing Performance at Low Temperatures

Recent studies on elastomeric bearings led to changes in the design specifications, which tend to indicate that bearings fabricated in the past, would fail the current test requirements. This is contrary to the fact that there have been no reported problems of poor bearing performance in low-temperature regions. AASHTO requires low-temperature tests to determine the change in the shear modulus, which is limited to a certain value. This criterion does not adequately address the performance of the bearings, because in-service conditions of an elastomeric bearing are not sufficiently taken into account. The field performance of the bearings depends primarily on the temperature characteristics of the geographic location where the bearing is installed, which also determines the probable amplitude of shear strain the bearing would experience. Thus, to adequately evaluate the in-service performance of the bearings, a performance-based procedure should be employed. In this paper, a variety of bearings were tested and checked at four different low-temperature locations. The test results have been reported in a companion paper. It was established that most of the bearings could in fact serve satisfactorily in spite of the fact that the bearings in many instances fail the current test procedures. This indicates that the current testing requirements related to cold-temperature performance are too severe. Hence, a procedure that relies on the historic temperature records of the region where the bearing would be installed is recommended to determine the performance requirements at a particular location. In this procedure, the acceptance criterion is based on the maximum expected shear force and the potential slip of the bearings.