# An Experimental Study on Repairing of Reinforced Concrete Beams Having Damaged Longitudinal Bars
## 3 Results and Discussion
### Load-Displacement Curves
#### 3.2.1 First Cracking and Ultimate Loading Capacity  
The results showed that the damaged specimen lost 97% of its original first crack load capacity and 89% of its original ultimate load capacity. For the repaired beams with the SNSM method (Group B), the RB1-SNSM-S beam regained most of the original first crack (about 93%) as the damaged steel was replaced with a similar amount of rebar pre-damage. The slight reduction may be due to the weaker surface interaction between the added mortar and the existing damaged surface. On the other hand, RB2-SNSM-G regained only 58% of the original first crack load capacity of the undamaged beam. In terms of ultimate load capacity of the repaired beams with SNSM (Group B), the results of RB1-SNSM-S showed a 19% reduction in ultimate loading capacity as compared to the undamaged beam (RefB), while the results of RB2-SNSM-G showed a 63% reduction in the ultimate load capacity of the reference beam (RefB). When the results of GFRP and steel reinforcement are compared, it can be observed that its contribution remained at lower levels, although the tensile strength of the GFRP bar is higher than that of the steel bar. This lower capacity is the result of a splitting failure due to a weaker bond between the added mortar and the GFRP bars (smooth surface), which governed the failure criteria. The load capacity of the beam repaired using the NSM method (RB3-NSM-G) was higher than that of the beam repaired with the SNSM method (RB2-SNSM-G). The reason for this is the increase in the distance of the moment arm. Wrapping with a U-shaped FRP sheet in the NSM method caused this value to be higher. The beams repaired with the EBR method by using a CFRP sheet (Group D) showed lower first crack loading, with about 81% of its original first crack loading capacity for the beam repaired with a bottom CFRP sheet with an extra boundary U shape sheet, and about 75% of its original first crack loading capacity for the repaired sheet without the boundary U shape. In the EBR beams repaired with an external layer reinforced with bars (Group E), the beam repaired using steel rebar (RB7-EBR-S) showed an increase compared to the original first cracking strength with a 25% proportion. This is due to the fact that the extra layer offered increased beam depth, leading to a higher moment arm. The RB7-EBR-S specimen is unique among all the repaired specimens for which the load capacity increased as compared to the undamaged specimen (RefB). Despite that, the beam repaired using GFRP rebar (RB8-EBR-G) showed a 20% decrease in the first crack loading of the reference specimen (RefB). Testing on EBR beams repaired with a CFRP sheet (Group D) resulted in a lower ultimate loading capacity of 83% of its original ultimate loading capacity for the beam repaired with a bottom CFRP sheet with an extra boundary U shape sheet, and about 62% of its original ultimate loading capacity for the repaired sheet without the boundary U shape. As for the EBR beams repaired with an external layer reinforced with bars (Group E), the beam repaired with steel showed a 23% increase as compared to the original ultimate loading strength, while the beam repaired with GFRP rebar showed a reduced ultimate loading of 54% as compared to the reference specimen. This reduction in the beam strength is due to a similar behavior of splitting failure that was observed in the SNSM-G specimen. When the results of the ultimate load capacity of all the repaired beams are compared to the damaged specimen (RefB-D) as a reference, it is observed that there is a significant increase in the ultimate loading of all the repaired specimens. The RB7-EBR-S beam repaired using the EBR method with an external layer of steel rebars offered the best results, with an increase of about 1015% compared to the damaged beam (RefB-D), followed by the RB1-SNSM-S specimen (SNSM method with steel rebars) and the RB6-EBR-CS-U specimen (EBR method with a CFRP sheet and U in boundaries), which offered almost similar repair results of 632% and 650%, respectively.