Aim: Steel structural elements can lose their strength in vehicle crashes, fire, fatigue, decay, humidity, etc. Consequently, their load-bearing capacities reduce considerably. A widely used strengthening method for steel beams is fiber-reinforced polymer strips or plates. One of the most important problems for this practice is sudden end-strip debonding due to the high normal and shear stress concentration. In this study, the structural behavior of deformed steel I-beams strengthened by carbon composites under bending was studied numerically. Using a commercial nonlinear finite element program (ABAQUS), a finite element model verified with the formerly executed experimental study was presented. To examine the effect of Mechanical Anchorage on large samples, a parametric study was carried out with the verified finite element model. In the parametric study, mainly three parameters were considered. Flange slenderness ratio (Bf/tf), web slenderness ratio (H/tw), and length to cross-sectional depth ratio (L/bf). Results derived from the nonlinear analysis revealed that the employment of the bolt anchorage increases the load capacity of the deformed elements and sustains the elements to resist more loads. However, the behavior and strengthening capacity of this practice is accordingly dependent on the flange slenderness ratio and web slenderness ratio of the proposed beam. Obtained results also indicate that the efficiency of mechanical anchorage in short-span beams is higher compared to the long-span beams.