Strengthening of damaged low strength concrete beams using PTMS or NSM techniques

This article presents the results of an analytical and experimental study on the performance of rectangular reinforced concrete (RC) beams strengthened using either post-tension metal strapping (PTMS) or side-near surface mounted (SNSM) FRP bars. Four low-strength (15.3 MPa) medium-scale beams were tested in four-point bending in two phases. In Phase I, one control beam was tested up to failure, whereas three beams were tested up to yielding of the main flexural reinforcement. In Phase II, the three pre-cracked beams were strengthened using PTMS or SNSM techniques, and then retested up to failure. The results indicate that the capacity of the pre-cracked PTMS-strengthened beam was only 8 % higher than the control counterpart. Conversely, the SNSM strengthening solution increased the beam capacity by up to 55 %, which is due to additional flexural reinforcement provided by the FRP bars. Moreover, the predictions given by linear cracked sectional analysis and the current ACI guidelines match well the deflection response of the strengthened beams but only up to the yielding load.