Abstarct: Many concrete structures reinforced with steel bars are subjected to aggressive environments. In these areas, factors such as humidity, temperature, and chlorides cause the corrosion of steel bars. Using Fiber-Reinforced Polymer (FRP) rebars instead of steel is considered one of the solutions to this problem. Unlike steel rebars, these rebars are not conductive and will not corrode. Brittleness and low ductility are the main problems of FRP bars. One of the proposed solutions to improve the ductility of concrete beams reinforced with FRP bar is to use a short bar in the middle of the beams. By placing the short bar in the middle of the beam, the behavior of the beam changes. Among these changes, we can mention the significant initial stiffness and the slope change in the load-displacement diagram. In this research, a finite element model has been developed in ABAQUS software. Ultimate load, ultimate displacement, beam failure mode, load-displacement diagram, stress-displacement diagram of short rebar, cracking load, and cracking contours were evaluated. Then, the ultimate load and cracking load were calculated in an analytical study. The validity of numerical and analytical models was confirmed in comparison with five concrete beams reinforced with FRP bars. The results showed that the maximum difference between numerical and experimental results is 6.5% and the maximum difference between experimental results and analytical calculations is 7.3%. Also, there is a direct relationship between the stress-displacement diagram of the short bar and the results of the load-displacement diagram of the beam. Using short middle bar leads to the formation of a critical crack in the beam. The cracking load in the numerical and analytical model in comparison with the experimental results has a maximum difference of 14.2% and 11.4%, respectively. in a parametric study, the ductility of 14 beams was investigated in 4 groups. Two Priestley-Pauli and equivalent energy methods were used to check beam ductility. According to the results of both techniques, it can be said that by adding short bar to the beam, the ductility increases. In the examined samples, the maximum increase in ductility is 22% baxsed on the energy method and 26.1% in the Priestley-Pauli technique compared to the case where there is no short rebar in the beam. Then, the effect of the short bar stress-displacement diagram on ductility was investigated. The results showed that a stronger bond between concrete and short bar improves ductility. In the last part, the final load of the beams was analyzed baxsed on the analytical method and then compared with the numerical results.