Abstract
This paper presents different strengthening techniques to improve the shear capacity of existing thick concrete slab structures that were constructed without shear reinforcement. Reinforcing bars are installed into vertical drilled holes and anchored with epoxy adhesive to increase the shear capacity. Experiments on retrofitted beams, representing slab strips, showed that all of the strengthening techniques investigated resulted in increased shear capacities. The shear failure mechanisms of the strengthened beams showed that, as expected, current evaluation methods for elements with conventional, well-anchored stirrups can lead to an overestimation of the shear capacities. The efficiency of the strengthening techniques is strongly influenced by the performance of the end anchorage of the drilled-in bars. The effectiveness of the epoxy-bonded bars is a function of their embedded length and they can, in some cases, debond before they reach their yield strength. By using the maximum bar spacing required by the Canadian design code for bridges or the AASHTO-LRFD design specifications, bonded shear-reinforcing bars may debond and offer poor performance. A maximum transverse reinforcement spacing criterion is therefore suggested for the added bonded bars.
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Acknowledgments
The research reported in this paper was made possible by funding from the Natural Sciences and Engineering Research Council of Canada (NSERC, CREATE-INFRA) and the “Fonds de Recherche du Québec—Nature et Technologies” (FRQNT). The authors also acknowledge the contributions of Philippe Provencher and Benoit Cusson who performed the beam tests. The experiments were carried out in the structures laboratory at Université Laval.
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Published In
Journal of Performance of Constructed Facilities
Volume 31 • Issue 3 • June 2017
Copyright
©2016 American Society of Civil Engineers.
History
Received: Apr 6, 2016
Accepted: Aug 30, 2016
Published online: Oct 31, 2016
Discussion open until: Mar 31, 2017
Published in print: Jun 1, 2017
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