Experimental analysis of shear deficient reinforced concrete beams strengthened by glass fiber strip composites and mechanical stitches

Abstract

This study was conducted to present a new technique to increase the capacity of reinforced concrete beams with insufficient shear reinforcement. Four beam specimens at 1/2 scale were produced. One of these beams was used for reference, while the other three were strengthened using different methods. The strengthening methods were performed using Mechanical stitches (MS), Glass fiber reinforced polymer (GFRP), and a hybrid of the two (GFRP and MS). In the experiments, the reference beam (E0), the MS-strengthened beam (E1), the GFRP-strengthened beam (E2), and the GFRP+MS-strengthened (E3) beam were tested under vertical load. Following the experiment, vertical load-bearing capacity, ductility value, initial stiffness value, and energy dissipation capacity were calculated for each beam. Afterward, extensive micro and macro damage analyses were performed. In the experiment, the E0 specimen resulted in a failure mode with direct shear damage. The strengthened E1 and E2 beams showed a typical bending behavior. The vertical load-bearing capacity of the E1 and E2 beams increased by 16.8% and 18.1%, respectively, compared to E0. The load-bearing capacity of the newly proposed technique, the hybrid E3 beam, was increased by 19.2%, although it failed with shear damage. Thus, this study has clearly demonstrated that beams with insufficient shear reinforcement can be strengthened using single-layer GFRP (E2). Considering its cost-efficiency compared to other composite materials, it has been suggested that GFRP should be used more widely in the market. In addition, it is reccommended that future studies can use the proposed E1 strengthening for beams weak against shear. The experiments revealed the most appropriate strengthening method for shear beams to be E1>E2>E3 in terms of performance/cost. Finally, the results suggest that the proposed hybrid strengthening (E3) can be turned to a ductile behavior through further experiments with different configurations.