Shear strengthening of RC deep beams with openings using Sprayed Glass Fiber Reinforced Polymer Composites (SGFRP) : Part 1. Experimental study

Abstract

This paper presents an experimental study on shear strengthening of Reinforced Concrete (RC) deep beams with openings using externally bonded Sprayed Glass Fiber Reinforced Polymer (SGFRP) composites. Based on the experimental results, reinforced concrete deep beams strengthened by SGFRP composites may fail by de-bonding of the fibers from the beam surface. To avoid such failures, mechanical anchoring system has been introduced to securely attach the SGFRP to the beam surface. In the experiment, the effectiveness of the mechanical Expansion Bolt (MB) anchoring system was examined. A total of 29 RC deep beams with openings in the web were tested using a three-point loading scheme. The examined parameters included size and shape of the openings, SGFRP thickness, SGFRP configuration and strength of concrete. The SGFRP technique with adequate MB anchoring system was found to be an effective means to elevate the shear strength of RC deep beams with openings. The failure mode was changed from de-bonding to inclined crack rupture in the fibers. However, if the thickness of SGFRP is increased, the tendency of anchor pullout and following de-bonding failure mode would be possible. In general, the experimental results demonstrated a higher increase in the shear strength when the thickness of the SGFRP was increased. Strengthening configuration also has a great impact on the strength and stiffness increase. The U shaped strengthening with SGFRP applied onto the side and bottom faces of the beam was superior to strengthening on side faces only. It was also found that the effectiveness of SGFRP strengthening was lower in high-strength concrete beams than in low-strength concrete beams.