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UBC Theses and Dissertations

Shear strengthening of reinforced concrete beams with various composite strengthening systems Kennedy, Dylan


Across Canada and around the world, damaged and aging infrastructure is a major issue facing civil engineers and infrastructure planners. Funding to replace these aging structures is unlikely to become available, therefore, economical repair techniques, which can return a structure to its original state are required. Several of those techniques are mortar adhered near surface mounted (NSM) fibre reinforced polymer (FRP) bars and fabric reinforced cementitious mortar (FRCM) wraps. These composites overcome financial and safety related concerns of previously used repair methods, while delivering similar levels of strengthening efficiency. This study was designed to investigate the effectiveness of these two composite strengthening systems on shear-damaged reinforced concrete (RC) beams with different levels of damage (1st shear crack and 70% of maximum theoretical load), adhesives (mortar and epoxy), wrapping patterns (continuous and intermittent), and different stirrup spacings (150mm or 200mm). Fifteen half-scale (200x265x2000 mm) RC beams (2 control, 6 strengthened without damage, and 7 strengthened after damage) were cast and tested under monotonic three-point bending conditions. Load, stiffness, mid-span displacement, pseudo-ductility, energy absorption, and failure mode were used as performance indicators. Results showed that most of the beams failed due to debonding failure between the strengthening material and the concrete substrate. The strengthening systems did not have a significant effect on the beams’ stiffness, however, all the strengthening systems were able to increase the load bearing capacity, the pseudo-ductility, and the energy absorption. Load bearing capacity was increased between 22% and 42%, depending on the strengthening system used. Recommendations on the maximum design strains in the different strengthening systems were also made.

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Attribution-NonCommercial-NoDerivatives 4.0 International