Shear strengthening design of pre-cracked reinforced concrete beams using bonded and bolted steel plates

A design guideline for shear strengthening of pre-cracked reinforced concrete (RC) beams using steel plates has been presented in this research by modifying the available shear capacity formulas. An experimental investigation was also carried out in order to validate the proposed guideline. Total five RC beams were fabricated, among which four beams were pre-cracked in shear by applying preloads. Two of the cracked beams were then strengthened with adhesive bonded steel plates while the rest two were strengthened with bolted steel plates. Variation was made in plate depth and bolt layers. The shear performance of the strengthened beams was evaluated by testing the beams to their ultimate capacity. Experimental results indicated that the shear capacity, ductility and stiffness of the pre-cracked beams increased significantly after strengthening with continuous steel plates. The shear capacity varied from 131% to 201% for strengthened beams compared to the control beam. Deeper plates offered better shear performance than the shallower plates. Modification of the existing formulas by introducing preload factors for estimating the shear capacity of the strengthened beams showed a good agreement with the experimental shear capacity.