Structural Behavior of Longitudinally Posttensioned Timber Beams under Serviceability Gravity Loading
Publication: Journal of Structural Engineering
Volume 143, Issue 8
Abstract
The scope of this paper is to quantify the advantages of using unbonded longitudinal posttensioning for long-span timber beams. This sustainable system can be a suitable alternative to more traditional prestressed concrete and (nonprestressed) glulam or LVL solutions. Unbonded posttensioning provides enhanced performance at serviceability limit state conditions, the ability to control deflections, and an increase in flexural strength. An experimental campaign limited to serviceability limit states for gravity loads was carried out at the University of Canterbury, New Zealand. In particular, two different static configurations were tested (simply supported and statically indeterminate beams) with different tendon profiles (straight and draped), internal and external to the beam section. A semianalytical iterative procedure for the solution of the geometrical nonlinear problem of unbonded posttensioning was implemented in order to capture and predict the experimental behavior. The experimental and numerical results confirm the enhanced deflection performance of the longitudinally posttensioned beams with respect to traditional timber beams, especially when external draped tendons are used.
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Acknowledgments
The present research project has been funded by Structural Timber Innovation Company (STIC). LVL was supplied by Nelson Pine, tendons provided by BBR—ConTech, and the manufacturing of the timber beams by Hunter Laminates. The technical support of John Maley is also gratefully acknowledged.
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Published In
Journal of Structural Engineering
Volume 143 • Issue 8 • August 2017
Copyright
©2017 American Society of Civil Engineers.
History
Received: Jul 14, 2016
Accepted: Jan 13, 2017
Published ahead of print: Mar 24, 2017
Published online: Mar 25, 2017
Published in print: Aug 1, 2017
Discussion open until: Aug 25, 2017
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