ELASTOMERIC BEARINGS: BACKGROUND INFORMATION AND FIELD STUDY

1. Report No. FHwAITX-95+ 1304-1 i 2. Government Accession No. Technical Report Documentation Page 3. Recipient's Catalog No. 4. Title and Subtitle ELASTOMERIC BEARINGS: BACKGROUND INFORMATION .MID FIELD STUDY 7. Author(s) f B. A. English, R. E. Klingner, and J. A. Yura 9. Performing Organization Name and Address Center for Transportation Research The University of Texas atAustin 3208 Red River, Suite 200 Austin, Texas 78705-2650 5. Report Date June 1994 6. Performing Organization Code 8. Performing Organization Report No. Research Report 1304-1 10. Work Unit No. ITRAISj 11 . Contract or Grant No. Research Study 3-5-92/4-1304 13. Type of Report and Period Covered 12. Sponsoring Agency Name and Address Texas Department of Transportation Interim Research and Technology Transfer Office p. 0. Box 5080 14. Sponsoring Agency Code Austin, Texas 78763-5080 15. Supplementary Notes Study conducted in cooperation with the U.S. Department of Transportation, Federal Highway Administration Research Study Title: "Elastomeric Bearings" 16. Abstract This report deals with Phase One of TxDOT Project 1304 (Behavior ofElastomeric Bearings). The overall objectives of that project are (1) to recommend procedures for designing elastomeric bearings used by TxDOT and (2) to recommendpractical guidelines andprocedures for inspecting existing and future elastomeric bearings. The overall objectives of Phase One of that project are: to verify field reports; to conduct field surveys; and to document bearing and girder movements. To accomplish the Phase One objectives, the following tasks were camed out: a comprehensive literature review was conducted; field reports were verified by site visits (Slaughter Creek, Beaumont, Paris, andAlanreed) and by coordination with the BRINSAP database; two bridges were selected for field instrumentation and study (Slaughter Creek andAlanreed) with emphasis on bearing and girder movement; and the BRINSAP database was used to identify bridges that might have bearing problems. The results of the field study can be summarized as follows: -- Two bridges were instrumented and monitored. -- Bearing and girder movement was monitored on both bridges. The effect of resetting the original natural rubber bearings at the Slaughter Creek bridge was compared with the effect of replacing the rubber bearing with a neoprene bearing. -- Girder movement was measured up to 3/8 inch (l cm) in contraction and expansion, due to temperature changes; both daily and seasonal variations were recorded. It was shown that these movements were easily predicted with simple engineering models. -- After the various resetting and replacement operations, the bearing movement measured at Slaughter Creek was inconsistent and not reproducible. Movement was found to be zero at one time and then unlimited at another time, with no apparent change in loading conditions. However, when it did occur, bearing movement was immediate. -- Resetting with natural rubber bearings was ineffective. However, when the natural rubber was replaced with neoprene bearings, bearing movement stopped. The principal conclusions were: -- Bearing movement is primarily driven by girder thermal movement. -- Girder thermal movement consistently agrees with simple calculations. -- Bearing movement is inconsistent, not stopped by resetting, but stopped by replacement with neoprene. -- Correctly designed neoprene bearings are not moving and natural rubber bearings are moving under the same loading conditions. 17. Key Words bridges, design, behavior, bearings, elastomers, neoprene, rubber 18. Distribution Statement No restrictions. This document is available to the public through the National Technical Infonnation Service, Springfield, Virginia 22161. 19. Security Class if. (of this report) Unclassified Form DOT F 1700.718-72) 20. Security Classif. (of this page) Unclassified Reproduction of completed page authorized 21. No. of Pages 104 22. Price