Primary Bond Mechanism Behavior of Posttensioned 7-Wire Strand during Load Exposition
Publication: Journal of Bridge Engineering
Volume 23, Issue 5
Abstract
The three primary bond mechanisms of a 7-wire strand are adhesion, friction, and mechanical interlocking between the concrete surface and the strands’ helical surfaces. Once adhesion fails as a result of micromovements of the strand, it is very difficult to predict the contribution of other two post-initial slip mechanisms to the total bond capacity of the 7-wire strand. The predictions become more difficult when the bond is influenced by the use of oil-based corrosion-protection (OCP) agents. This article discusses the influence of primary bond mechanisms during the loading stages of the posttensioned two-span concrete member and evaluates the contribution of bond mechanisms to the total member resistance and behavior. Elastomagnetic (EM) gauges, which can directly record the force inside the strands during prestressing and loading cycles, were used as one of the primary monitoring mechanisms. Based on these records, it is possible to evaluate force behavior in the strands during successive load stages up to the ultimate limit state (ULS) of the concrete members. The nonlinear bond behavior of the 7-wire strand is presented, including details of its elongation during testing.
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Acknowledgments
The author gratefully acknowledges David Smith and Robert Petty (both of Atkins) for technical support and review. Special thanks is given to Associate Professor Andrej Jarosevic for the support and advice regarding EM gauge record evaluation. Sincere appreciation is also expressed to the Department of Concrete Structures at the Faculty of Civil Engineering at the Slovak University of Technology in Bratislava, Slovakia. The work was supported by the Slovak Research and Development Agency under Contract No. APVV-0442-12. The opinions, findings, and conclusions in this article are those of the author.
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Published In
Journal of Bridge Engineering
Volume 23 • Issue 5 • May 2018
Copyright
© 2018 American Society of Civil Engineers.
History
Received: Jun 9, 2017
Accepted: Nov 14, 2017
Published online: Mar 13, 2018
Published in print: May 1, 2018
Discussion open until: Aug 13, 2018
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