NSM FRP Shear Strengthening of RC Beams with Internal Stirrups

Abstract

This article presents an experimental study on shear strengthening of reinforced concrete (RC) by near-surface mounted (NSM) fiber reinforced polymer (FRP) rods, comparing the experimental results with three existing formulations for the NSM FRP shear strengthening technique. The NSM FRP technique is done by making a groove in concrete cover, putting FRP rods in the groove, and fixing them with epoxy adhesive. To evaluate The efficiency of NSM FRP strengthening, two experiments were conducted. In the first experiment, bond testing in pull-out conditions was conducted to compare a suitability of different groove sizes (1.5 and 2.0 times of rod diameter) for NSM FRP application. In the second experiment, strengthened beams with stirrups were tested to evaluate influences of key parameters on shear capacity and failure mode. Three examined parameters used in such testing were two types of FRP (Carbon and Aramid), spacing between the rods and slope of FRP rods. Peeling-off failures of NSM layers was found in some cases. This failure mode limited the efficiency of NSM FRP technique.

Keywords: peeling-off, shear, strength, concrete, reinforce, near-surface mounted