The National Academies

NCHRP 20-07/Task 099 [Completed]

LRFD Design Criteria for Cotton Duck Pad (CDP) Bridge Bearings
[ NCHRP 20-07 (Research for AASHTO Standing Committee on Highways) ]

  Project Data
Funds: 30000
Research Agency: Consultant: Roeder & Misc.
Effective Date: 9/29/1998
Completion Date: 2/28/1999
Comments: Completed

Task 99, FY 1999, "LRFD Design Criteria for Cotton Duck Pad (CDP) Bridge Bearings" (Charles Roeder). Cotton duck pad (CDP) or preformed fabric pads consist of multiple layers of cotton duck impregnated and bonded with high quality elastomer. Current AASHTO LRFD specifications for CDP bearings is based on research done on elastomeric pads (NCHRP Reports 248, 298, and 325). However, states are basing CDP designs on industry criteria and not AASHTO criteria. It is very likely these CDP bearings will not meet the current AASHTO LRFD criteria for rotation. In Washington State, CDP bearings have been used for over twenty years as economical expansion bearings. This successful performance record suggests a need for AASHTO to develop and modify AASHTO LRFD design procedures so owners may provide safe, consistent, and cost-effective CDP bearings. The objective of this research is to utilize existing test data and research to develop AASHTO LRFD design guidelines, and to modify current AASHTO Division II-Construction specifications. The consultant has revised the final report based on the project panel comments. The report is published as NCHRP Web Document 24 and is available in portable document format (PDF). The Technical Committee on Bearings and Expansion Devices of the AASHTO Highway Subcommittee on Bridges and Structures is working on specification changes as a result of this report. (NCHRP Staff: D.B. Beal)

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