A Study on Repair Effectiveness of Damaged RC Beams with Circular Openings Using CFRP Sheet

To accommodate essential utility services such as HVAC systems, electric lines for electricity and computer network, plumbing for sanitary lines and water supply, etc., transverse openings are provided on the RC beams. These openings become a source of potential weakness. Thus, it is important to understand the behaviour of the beam imposed with openings and the effects on its strength and serviceability. Circular, square or nearly square holes may qualify as small openings if their depth is not more than 40% of the total depth of the beam. As a result, the design and analysis of a beam with small openings may proceed similarly to that of a solid beam. By the inclusion of openings, non-uniformity of the section is caused, which results in interruptions or disturbances in the usual stress flow and also early cracking in the vicinity of the opening. To regulate width of cracks and avoid potential premature failure of the beam, special reinforcement, around the periphery of the opening, should be provided in adequate amount. Retrofitting can be adopted to gain the beam’s strength and serviceability. One of the potential materials for fixing damaged infrastructure is carbon fibre reinforced polymer (CFRP) sheet. Nine beams were cast and 3 beams were considered as control beams, among which 3 beams (B_H) were pre-cut beams of circular small openings (ratio of diameter of openings to depth of beam is less than 50%) with special reinforcement given around the opening. Remaining beams were post-cut for same diameter and repaired using CFRP at the hole circumference and beam surface. All the beams were tested under two-point loading, and the results were drawn in terms of ultimate load, cracking load, shear pattern, and load versus deflection parameter. Based on the experimental investigation conducted on reinforced concrete (RC) beams, control beams (B_M) underwent maximum deflection when subjected to static loading test. Beams designed for openings, B_H show least deflection which proves to be the best method for providing an opening in a beam in this study and application of CFRP helped in arresting shear cracks in the beams and enhanced the ductility of the beam.