On the strengthening of RC beams with near surface mounted GFRP rods

Inserting FRP rods into grooves using the NSM technique has been demonstrated to be a suitable method for repairing or strengthening RC beams. Recently, the availability of NSM GFRP rods has been highlighted notwithstanding low elasticity and shear modulus. This paper elaborates considerations on NSM GFRP rod strengthening on the basis of the results of experimental investigation using pull-out tests on concrete specimens with GFRP rod, bending tests on non-strengthened beams and strengthened with NSM GFRP rods and, lastly, through vibration tests on the same aforementioned beams. A theoretical bond analysis for evaluating strain data and shear stress-slip laws was developed taking into account NSM GFRP rods strengthening.The experimental bending tests were carried out on the RC beams for defining static behaviour until failure. Given that the occurrence of damage in concrete elements leads to change in dynamic response, vibration tests in the case of free–free ends were developed to evaluate the experimental vibration both for non-strengthened and strengthened beams with NSM GFRP rods. Comparison between experimental and theoretical data permits to discuss the actual behaviour of RC beams strengthened using NSM strengthening technique and to assess the availability of GFRP rods.