Recent research has resulted in significant increases in the recommended load and deformation capacity of elastomeric bridge bearings. These increased capacities require better quality control during the manufacturing of the bearing and more thought design considerations. Elastomers may stiffen dramatically at low temperatures, and the increased stiffness may result in much larger forces on the bridge piers, superstructure and the bearings. These increased forces must be considered in the design of the bridge and the bearing. This report describes an extensive experimental and analytical investigation into low temperature stiffness of elastomeric bridge bearings. The research shows that some elastomer compounds may stiffen to many times their room temperature stiffness. The amount of stiffening depends upon the temperature, duration of cold conditions, and the elastomer compound. An environmental simulation test was performed to show how these low temperature stiffness effects translate into forces in the bridge and the bearing. A detailed analysis of low temperature conditions in the United States was made and correlated to the test results. The research resulted in a recommended test apparatus and test procedure, recommended low temperature behaviour requirements for the various parts of the United States, and a proposed change to the AASHTO Specification. The research also includes a review of manufacturing tolerances and acceptance test requirements. Various defects encountered in practice are correlated to these requirements, and recommendations to the AASHTO Division II Specification are made. This research completes the NCHRP 10-20 research into elastomeric bridge bearings, and the final version of the proposed specification for design and construction of elastomeric bearings is provided. Design examples are included to illustrate the proposed design method. (A)
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