Experimental and numerical study of the RC beams shear-strengthened with NSM technique

The present paper examines the structural performance of reinforced concrete (RC) beams strengthened in shear through near surface mounted (NSM) technique experimentally and simulates their behavior using finite element analysis. Then, the effect of using concrete with different compressive strengths and varying ratios of steel transverse reinforcements is studied using parametric analyses. In the experimental section, four reinforced concrete beams are cast with and without stirrups to study the effect of NSM technique as a shear strengthening method. For this purpose, specimens with the dimensions 2000 × 300×200 mm are prepared and are tested in four point loading up to failure. The load–displacement curves of the mid-span as well as failure mechanisms of the beams are then compared. The experimental results indicate that NSM technique increases the shear capacity up to 69% and 41% in the beams with and without stirrups, respectively. Moreover, in NSM strengthened specimens, ductility decreases for both beams with and without stirrups in comparison to the controls. Also, finite element case analyses through modeling the bond behavior between concrete and CFRP show that as the compressive strength of concrete decreases, the probability of de-bonding increases; furthermore, as the internal shear reinforcement ratio increases, the axial strain of CFRP decreases.