Performance of Elastomeric Bridge Bearings at Low Temperatures

Research was conducted to develop performance-based specifications along with recommended testing-acceptance criteria for elastomeric bridge bearings at low temperatures. Full size elastomeric bridge bearings were tested by specifically designed test setups that operate inside a walk-in type freezer. Tests were conducted at -10oC, -20oC and -30oC for a duration of 21 days. Additional tests were performed at variable temperatures derived from temperature data for some particular regions in the United States. The effects of cyclic compression and cyclic shear, rate of loading, type of elastomer compound, temperature history and coefficient of slip on the performance were investigated. Creep tests were also conducted. The results indicated that the increase in shear modulus could be as mush as 13 times the value at room temperature. However, shear modulus does not control the maximum shear force transmitted to the sub-structure, because slip between the bearing and the girder interface is a factor that limits the shear force. It was shown that rate of loading, shear strain level, temperature history and elastomer compound have significant effect on the performance. The rate of creep at cold temperature is significantly different than at room temperature. The performance of the tested bearings was evaluated for the in-service conditions obtained from temperature records of four cities in the US. Although the low temperature tests indicated that bearings would fail current AASHTO low temperature requirements, a performance-based evaluation revealed that all tested bearings would perform satisfactorily over a period of fifty years at the four selected cities. A performance-based testing and acceptance criteria was developed.