Behavior of Prestressed Concrete Strengthened with Various CFRP Systems Subjected to Fatigue Loading
Publication: Journal of Composites for Construction
Volume 10, Issue 6
Abstract
Many prestressed concrete bridges are in need of upgrades to increase their posted capacities. The use of carbon fiber-reinforced polymer (CFRP) materials is gaining credibility as a strengthening option for reinforced concrete, yet few studies have been undertaken to determine their effectiveness for strengthening prestressed concrete. The effect of the CFRP strengthening on the induced fatigue stress ratio in the prestressing strand during service loading conditions is not well defined. This paper explores the fatigue behavior of prestressed concrete bridge girders strengthened with CFRP through examining the behavior of seven decommissioned girders strengthened with various CFRP systems including near-surface-mounted bars and strips, and externally bonded strips and sheets. Various levels of strengthening, prestressing configurations, and fatigue loading range are examined. The experimental results are used to provide recommendations on the effectiveness of each strengthening configuration. Test results show that CFRP strengthening can reduce crack widths, crack spacing, and the induced stress ratio in the prestressing strands under service loading conditions. It is recommended to keep the prestressing strand stress ratio under the increased service loading below the value of 5% for straight prestressing strands, and 3% for harped prestressing strands. A design example is presented to illustrate the proposed design guidelines in determining the level of CFRP strengthening. The design considers the behavior of the strengthened girder at various service and ultimate limit states.
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Acknowledgments
The writers would like to acknowledge the support of the North Carolina Department of Transportation through Project 2004-15. Valuable help was provided on this project by Dr. Tarek K. Hassan, Ronaldson Carneiro, and Dr. Amir Mirmiran. Several industry members made much appreciated donations: David White of the Sika Corporation, Doug Gremel of Hughes Brothers, Akira Nakagoshi of Mitsubishi Chemical America, Peter Emmons of Structural Preservation Systems, and Ed Fyfe of Fyfe Corporation. Special thanks to Structural Preservation Systems and Fyfe Corporation for carrying out the strengthening and repair work. Thanks are also extended to the personnel at the NCDOT Bridge Maintenance Department, especially Dallie Bagwell and Tracy Stephenson for providing Bridge Maintenance facilities and constructing steel substructures for the repair and strengthening work. The authors would like to thank Jerry Atkinson and Bill Dunleavy, technicians at the Constructed Facilities Laboratory at North Carolina State University, for their invaluable help.
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Information & Authors
Information
Published In
Journal of Composites for Construction
Volume 10 • Issue 6 • December 2006
Pages: 492 - 502
Copyright
© 2006 ASCE.
History
Received: Nov 8, 2005
Accepted: Feb 7, 2006
Published online: Dec 1, 2006
Published in print: Dec 2006
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