عنوان مقاله [English]
In recent decades, composite material has been used in order to increase the effectiveness of reinforced concrete structures. The difficulty of numerical modeling of beams in finite element method is a problem encountered during such a study. Destruction of structures such as buildings and bridges has been reported due to earthquake and time-dependent erosion. Highlighting the need for reinforcing the structures, many researchers have tried to estimate the efficiency limit and strength of reinforced concrete structures.In order to retrofit concrete structures polymer coating was first developed in Europe and Japan in 1980. In Europe, FRP systems have been used to replace steel sheets, that as a common resisting method, their connection to the tensile concrete parts of the members with different adhesives was popular to increase the flexural strength of the members. Since steel sheets deform under operation, they would destroy the connection of sheets and concrete. On the other hand, their installation is generally difficult and needs heavy machinery, so researchers sought a replacement of steel coatings with FRP. FRP with 20\% weight of steel jackets is approximately 8 to 10 times stronger than steel. One of the problems of numerical studies in these systems is their computer modeling in the form of finite element analysis (FEM). On the other hand due to a variety of effective parameters on their behavior, applying lab methods causes problems as they are time-consuming and expensive.In this research, retrofitting reinforced concrete beams using FRP is studied. At first in order to validate the accuracy of modeling, the analysis results obtained by ABAQUS software are compared with those of experimental studies. Then, beams that need strengthening are retrofitted and the effect of FRP on the curvature and rotational capacity of these beams is investigated. Finally, ductility proportion to the performance levels and the acceptance criteria for retrofitted beams regarding force or displacement control scenarios are obtained. Based on the results, the behavior of beams changes after retrofit, and since the displacement demand to capacity ratio (DCR) is less than 2, force control scenario must be considered regarding their acceptance criteria.