Non-linear Finite Element Analysis of Reinforced Concrete Beams Strengthened with Carbon Fiber-Reinforced Polymer (CFRP) Technique

Abstract

Strengthening of reinforced concrete beams with carbon fiber reinforced polymer (CFRP) is one of the most used strengthening techniques recently. It offers an attractive solution to enhance shear and flexural capacities of RC beams. Behavior in shear and flexure of reinforced concrete beams externally strengthened with CFRP is highly affected by the way in which these composites are bonded to the beam. The main objective of this research is to analyze strengthening of RC beams with CFRP using non-linear finite element models. The research made use of the commercial finite element modeling software (ANSYS) to prepare the finite element models and to study the influence of the important parameters on the overall response of strengthened RC beams in shear and flexure, in order to achieve the optimum utilization of such strengthening technique, in terms of load bearing capacity and possible deflection values. These parameters are: effect of number of CFRP layers, effect of CFRP layer length, and effect of CFRP layer inclination. The analysis of results proved that the general behavior of the FE models shows a good agreement with corresponding experimental investigations results, and that ANSYS is capable of producing results in good agreement with previously published experimental test results. The parametric study has proved that increasing the number of CFRP layers bonded to the beam soffit increases the stiffness of the beam, increases its flexural capacity, and decreases mid-span deflection at failure. Further, decreasing the length of the CFRP layer bonded to the beam soffit decreases the ultimate load of the beam with a slight increase in mid-span deflection at failure. Length of CFRP fabric when reaches 50% of beam span length, the increase in ultimate strength of the beam becomes worthless. Moreover, it has proved that shear strengthening of RC beams with CFRP fabric inclined at an angle of 90° to the beam axis is more efficient than strengthening with CFRP fabric inclined at an angle of 45°. Further, strengthening the RC beams with one layer of U-wrap CFRP fabric inclined at an angle of 45° with an additional layer of CFRP fabric on both sides of the web inclined at an angle of 0° is more efficient than strengthening with one layer of U-wrap CFRP fabric inclined at an angle of 90° with an additional layer of CFRP fabric on both sides of the web inclined at an angle of 0°.