Due to developments in manufacturing and compounding, they are now designed for higher loads. Their function is to accommodate bridge movements and transmit forces to the supporting structure. Neoprene and natural rubber are the most widely used elastomeric bearing materials. The behavior of elastomeric bridge bearings depends on time, temperature, rate of loading, stress level, size and the elastomer compound. Therefore, laboratory test procedures have been developed to determine their mechanical properties.
Mechanical properties change considerable at low temperatures.
As temperature decreases shear and compressive modulus increase significantly. The increase in shear modulus leads to the concern that larger shear forces are transmitted to supporting structure which can be detrimental, since elastomers can stiffen in the order of 20 times or more. Current laboratory test procedures are inadequate to address the performance of these bearings at low temperatures. This research is sponsored by National Cooperative Highway Research Program. The object of the research is to develop performance based specifications along with recommended testing-acceptance criteria.