Performance of Elastomers in Isolation Bearings: A Literature Review

Laminated elastomeric bearings have been used for about 30 years in the United States to isolate bridge substructures from the lateral forces induced by shrinkage and creep of their superstructures. More recently, elastomeric bearings have been increasingly employed in buildings and bridges as a means of decoupling the structure from seismic ground motions. Since most buildings and bridges have service lives of at least 30 to 60 years, questions about the long-term behavior of base-isolation bearings arise. This paper presents a review of literature relating to the long term performance of the elastomers used in seismic isolation bearings. Bearing performance requirements are discussed and material characteristics and fabrication procedures are outlined. Field experience and laboratory findings are reviewed. Finally, long-term environmental effects are discussed, including ozone degradation, corrosion, temperature effects, and the influence of bombardment of elastomers by high energy radiation.