Effects of Duct Types and Emulsifiable Oils on Bond and Friction Losses in Posttensioned Concrete
Publication: Journal of Bridge Engineering
Volume 13, Issue 1
Abstract
Emulsifiable oils are often used in posttensioned construction to reduce friction losses and provide temporary corrosion protection for tendons prior to grouting. This paper addresses the effects of two emulsifiable oils and three duct types on bond and friction losses. Bond test results indicate that corrugated galvanized steel ducts provide better anchorage than corrugated HDPE ducts. Rigid steel pipes performed poorly because of failure at the duct-concrete or grout-duct interface. Bond test results also indicate that the ultimate strength of posttensioned specimens with oiled tendons is similar to or better than the ultimate strength of specimens with unoiled tendons. However, specimens with oiled tendons experienced greater slip at a given load than specimens with unoiled tendons. Friction test results indicate that current recommended design values for the coefficient of friction for steel pipes and galvanized ducts are accurate. However, the measured coefficient for HDPE ducts is significantly less than the AASHTO-recommended value. Friction tests also indicate that lubrication of the tendon reduces the friction coefficient by 15% in rigid steel pipes and HDPE ducts if stressing occurs while the oil is fresh.
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Acknowledgments
This research project was carried out at the Phil M. Ferguson Structural Engineering Laboratory at The University of Texas at Austin. The writers gratefully acknowledge the financial support of the Texas Department of Transportation and the Federal Highway Administration. The writers would also like to thank Edwin Salcedo Rueda and Dr. Andrea Schokker of Pennsylvania State University, Dr. Sharon Wood of The University of Texas, and University of Texas research assistants Andrew Chronister and Kyle Steuck. Conclusions and opinions expressed in this paper are those of the writers alone.
References
AASHTO. (1999). Guide specifications for design and construction of segmental concrete bridges, 2nd Ed., Washington, D.C.
AASHTO. (2002). Standard specification for highway bridges, 17th Ed., Washington, D.C.
American Segmental Bridge Institute. (2000). “Interim statement on grouting practices.” Phoenix.
Kittleman, W. M., Davis, R. T., Hamilton, H. R., Frank, K. H., and Breen, J. E. (1993). “Evaluation of agents for lubrication and temporary corrosion protection of post-tension tendons.” Research Rep. 1264-1, Center for Transportation Research, Bureau of Engineering Research, Univ. of Texas, Austin.
Lüthi, T., Diephuis, J., Icaza, J. J., Breen, J. E., and Kreger, M. E. (2005). “Factors affecting bond and friction losses in multistrand posttensioning tendons including the effects of emulsifiable oils.” Research Rep. 4562-1, Center for Transportation Research, Bureau of Engineering Research, Univ. of Texas, Austin.
Perenchio, W. F., Fraczek, J., and Pfeifer, D. W. (1989). “Corrosion protection of prestressing systems in concrete bridges.” Rep. 313, Transportation Research Board, National Research Council, Washington, D.C.
Salcedo Rueda, E., Schokker, A. J., Kreger, M. E., and Breen, J. E. (2004). “Bond and corrosion studies of emulsifiable oils used for corrosion protection in posttensioned tendons.” PTI J., 2(1).
Information & Authors
Information
Published In
Journal of Bridge Engineering
Volume 13 • Issue 1 • January 2008
Pages: 100 - 109
Copyright
© 2008 ASCE.
History
Received: Aug 17, 2006
Accepted: Nov 2, 2006
Published online: Jan 1, 2008
Published in print: Jan 2008
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