Case Study of Elastomeric Bridge Bearings After 20 Years of Service

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Title: Case Study of Elastomeric Bridge Bearings After 20 Years of Service

Author(s): A. Stevenson and a. R. Price

Publication: Special Publication

Volume: 94

Issue:

Appears on pages(s): 113-136

Keywords: bridge bearings; deformation; evaluation; performance; rubber; serviceability; shear properties; tests; Construction

Date: 9/1/1986

Abstract:
Elastomeric bridge bearings (predominantly natural rubber) have now been in service in Great Britain for more than 25 years. It is, therefore, of considerable interest to the highway authorities to know what their present condition is, whether or not a replacement program needs to be implemented, and if not, what the remaining lifespan is likely to be. To answer these questions, the Department of Transport in the U.K. commissioned an evaluation program that started with a detailed study of typical natural rubber bridge bearings with totally enclosed steel laminates. The bearings were installed in 1962 under a bridge deck of a major motorway in the U.K. and have been functioning within their design limits and not subjected to unduly adverse environmental conditions. Initially, an instrumented study of the performance of the bearings in situ was conducted. Then, two of the 32 bearings supporting the bridge deck were removed and returned to the laboratory for study. These tests included shear and compression deformations of the whole bearings, as well as tests on the condition of rubber removed from one sectioned bearing. The overall conclusion from these tests was that both the whole bearing and the rubber materials were in excellent condition and extrapolating from the greatest changes measured. Also, it was learned that the total life of the bearings was likely to match the life of the structure, provided the service conditions did not change. For bearings subject to abnormal loading or harsher environments, these results may not be typical. The paper describes tests of the bearings, both on site and in the laboratory, undertaken to assess both performance and condition. Suggestions are made from this work for on-site methods to assess the condition of elastomeric bearings during service.