Evaluation of various FRP strengthening configurations for RC beam-column joints

There are several methods for strengthening reinforced concrete joints. Due to the unique properties of FRP (Fiber Reinforced Polymer) composites, the use of FRP laminates is one of the most commonly used techniques. The high cost of preparing concrete surfaces and attaching FRP laminates is a restricting factor for its application in reinforced concrete joint retrofit. Therefore, determining proper configurations that reduce the needed FRP material, as well as the surface preparation required for attaching FRP is an important factor in decreasing the strengthening cost. The proper arrangements of FRP strips can improve their performance in the rehabilitation and retrofit of reinforced concrete joints. To determine the proper configuration of FRP strips, finite element modeling was employed. The connection specimens are modeled in ABAQUS general-purpose finite element software and are classified into 10 general groups. To improve the performance of FRP strip configuration, the determined arrangement is investigated for different thicknesses and different widths of the FRP strips, and their results are compared with those of the connection specimen strengthened with full FRP coverage. The analysis results indicated that the load-bearing capacity of the connection retrofitted by the combined configuration of X-shape and orthogonal strips of FRP is close to that of the specimen with full FRP coverage. In this suitable configuration, the required FRP strips are reduced by about 30%, which decreases the cost and construction works needed for concrete joint rehabilitation.