Experimental and numerical study of RC beams strengthened with bottom and side NSM GFRP bars having different end conditions

The present paper studied experimentally and numerically the behavior of RC beams strengthened with near surface mounted (NSM) GFRP bars with and without end anchorage. Both bottom and side NSM strengthening technique were investigated and compared. The end anchorage was made by bent 150 mm from the two ends of the NSM bars by 45° or 90°. The experimental results showed higher load carrying capacity for the RC beams strengthened by bottom NSM bars compared to those strengthened with side NSM ones due to the internal arm effect. The highest ratio of improvement in the load carrying capacity of strengthened beams compared with the control beam was 201% for strengthened beam with bottom NSM bars having end anchorage inclined by 45° while the lowest ratio was 142% for the same strengthened beam with side NSM. The experimentally investigated beams and other beams were numerically simulated using 3-D elastic-plastic finite element analysis. There is a good agreement between the numerical and the experimental results. Therefore, the numerical work was extended to focus on the effect of NSM location. These results showed that, strengthened beams by NSM bars with the same internal arms and without end anchorage recorded the same load carrying capacity regardless of the location of the NSM bars either bottom or side. Furthermore, strengthened beams by side NSM bars with end anchorage embedded horizontally in the confined portion of the beam cross section showed significant improvement in the load carrying capacity of the strengthened beams compared to those with end anchorage embedded vertically in the concrete cover of the beam side.