Design of Cotton Duck Bridge Bearing Pads
Publication: Journal of Bridge Engineering
Volume 10, Issue 5
Abstract
Bearings are used to support loads and accommodate movements in bridges. Cotton duck bearing pads (CDP) offer a versatile and economical solution for bearing design. The CDPs have closely spaced layers of elastomer and fabric which result in large compressive strength and strain capacities. However, the engineering response of CDP has not been well understood and CDP design provisions are incomplete because of this limited knowledge. To better establish the engineering response and develop improved design provisions, an extensive experimental research study was conducted. The experimental program modeled loads and deformations induced on a bridge bearing and included both static and dynamic loading regimes in compression, shear, and rotation. The primary study parameters included pad geometry, pad manufacturer, and stress and strain levels. The results indicate that CDPs have significant compressive stress and deformation capacities. Using the experimental results, design limits to control pad damage and quality assurance provisions are proposed to ensure adequate service during the lifetime of the bridge. Delamination of the top pad layers occurs after many cycles of repeated load or deformation and limits on the maximum stress, stress range, and uplift are proposed to limit this type of damage. Diagonal fracture occurs when a CDP is subjected to large strains. Strict maximum strain limits are proposed to prevent this failure mode. Finally, quality control provisions are proposed to ensure adequate engineering performance of the pads.
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Acknowledgments
This research was funded by the Washington State Department of Transportation through the Washington State Transportation Center (TRAC) and the Arkansas Science and Technology Agency through Arkansas State University. Mr. Ralph Dornsife and Professor Tom Parsons were the Technical Advisors for this research. The bearings were provided by Voss Engineering of Lincolnwood, Ill., and Garlock Rubber Technologies of Paragould, Ark. Mr. Keith Legrid of Garlock Rubber Technologies, Mr. Doug Martin of Voss Engineering, and Mr. Glenn Adams formerly of Voss Engineering, Inc, Lincolnwood, Ill., all provided help and advice in obtaining and selecting bearings to reflect engineering practice. The experimental research was conducted in the structural laboratory at University of Washington with the assistance of Kevin Curtin and Vince Chaijaroen. The writers wish to express their appreciation to these participants for their support.
References
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© 2005 ASCE.
History
Received: Oct 7, 2003
Accepted: Oct 20, 2004
Published online: Sep 1, 2005
Published in print: Sep 2005
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