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Sprayed glass fiber reinforced polymers in shear strengthening and enhancement of impact resistance of reinforced concrete beams

University of British Columbia

Shear failure of reinforced concrete (RC) beams is often sudden and catastrophic. A timely shear strengthening of deficient RC beams is therefore critical in view of maintaining public safety. In this dissertation, the effectiveness of externally bonded sprayed glass fiber reinforced polymer (Sprayed GFRP) in shear strengthening of RC beams under both quasi-static and impact loading was investigated. Direct comparisons were drawn with hand-applied, site-impregnated FRP fabric. To study RC beams under impact loads, a unique test setup was developed. In this setup, both the striking hammer and the specimen supports are instrumented and accelerometers are mounted on the specimen to accurately measure specimen inertial loads and to provide a proper dynamic analysis of the system. A total of 77 RC specimens were tested with and without FRP strengthening. Given that bond between FRP and concrete is the critical link, in the shear strengthening program, different techniques were used to enhance the bond between concrete and Sprayed GFRP. It was found that roughening the concrete surface using a pneumatic chisel and using mechanical fasteners were the most effective techniques. Also, Sprayed GFRP applied on 3 sides (U-shaped) was more effective than 2-sided Sprayed GFRP in shear strengthening under both static and impact loading. GFRP, both sprayed and fabric, increased the shear load carrying capacity of RC beams and their energy absorption capacities, but Sprayed GFRP, especially U-shaped, was more effective than fabric GFRP. An increase of up to 105% in load carrying capacity of strengthened RC beams was observed under impact loading with respect to un-strengthened RC beams. Simple equations were proposed to calculate the contribution of Sprayed GFRP in shear capacity of RC beams under quasi-static and impact loadings. Analysis of data indicated that the load carrying capacity of strengthened RC beams both under quasi-static and impact conditions was governed by the effective strain capacity of the Sprayed GFRP, which was, in turn, governed by the GFRP configuration and its bond with concrete. Future research should therefore focus on enhancing the strain capacity of the FRP when used as externally bonded reinforcement for structural strengthening.

Text

2011-02-03

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http://hdl.handle.net/2429/31069

Civil Engineering

University of British Columbia

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