Parameters influencing performance of elastomeric bearings at low temperatures

Experimental research was conducted to investigate the performance of elastomeric bridge bearings at low temperatures. Full-size natural rubber and neoprene bearings were tested by specially designed test setups inside a walk-in-type environmental chamber. Steel laminated bearings were ordered with two specified shear modulus, 0.69 and 1.08 MPa. Tests were conducted at 23, -10, -20, and -30degreesC for a period of 21 days. The effect of cyclic compression, cyclic shear, rate of loading, type of elastomer compound, temperature history, creep, and slip coefficient on the performance was investigated. Approximately 500 shear stiffness tests were performed. Results indicated that the increase in shear stiffness at low temperature is a function of elastomer compound, temperature, and time. In addition, rate of loading, amplitude of strain, coefficient of friction, and temperature history were identified as important parameters that influence the bearing performance. Creep behavior at low temperature was significantly different from creep at room temperature but had no significant influence on the overall performance. It was shown that cyclic compression force and cyclic shear strain do not have significant influence on time-dependent stiffening (crystallization) of bearings. The results of this paper were used to develop a performance-based evaluation and acceptance criterion that is presented in a companion paper