Flexural Strengthening of Reinforced Concrete Beams with Longitudinal Circular Hole Using Near-Surface Mounted CFRP Strips

Abstract

The electromechanical piping systems of buildings either hang or pass through reinforced concrete (RC) beams and thus induce longitudinal and transverse holes. According to the literature, the small longitudinal hole has a minor effect on the strength and stiffness of the RC beam and thus can be ignored. However, a large hole has a significant impact on strength and stiffness and should be considered in the design. The reduction in stiffness and strength of RC beams with a large longitudinal hole can be recovered with fiber-reinforced polymer (FRP) composite material. This paper aims to study the effectiveness of different strengthening schemes with near-surface mounted carbon FRP (NSM-CFRP) for simply-supported RC beams with a longitudinal circular hole. The nonlinear finite-element (NLFE) model was proposed and then validated with 10 experimental tests from literature and in house by the authors. The NLFE model was employed to study the key parameters affecting the hollow RC beams, including the hole size, location, and strengthening with the NSM-CFRP strips scheme. The results showed that for the unstrengthen RC beams with a large hole, the optimal location was near the neutral axis with minimal reduction in strength and stiffness. For the same number of NSM-CFRP strips, the bottom strengthening scheme was less effective than the side scheme. The effectiveness of the combined (bottom and sides) strengthening schemes depended on the hole location, with the optimal hole location at the bottom compared to the middle of the beam.