Finite Element Analysis of Carbon Fiber Reinforced Polymer Strengthened RC Beam Subjected to Bending and Torsion

Abstract

It is well known that the presence of properly unaccounted torsional moment reduces the load carrying capacity of RC members due to many reason, resulting in a torsion critical member. In order to avoid the brittle failure due to torsion, CFRP strengthening the member is one way. In order to effectively strengthen beams exhibiting flexure and torsional behaviors together it’s important to identify factors that affect the performance of CFRP strengthened beams. A nonlinear study is carried out using ABACUS in order to investigate the effect of important parameters such as T/M ratio, amount, and distribution of transverse and longitudinal reinforcement. For this study beam models are divided into two series. The first series contains nine (9) CFRP strengthened RC beams which are grouped into three based on relative amount and distribution of compressive and tensile reinforcements. The second series contains six (6) CFRP strengthened RC beams which are grouped into two based on the ratio of transversal to longitudinal reinforcement ratios. By comparing these results with the available experimental and numerical results the proposed model is found to be capable of analyzing CFRP strengthened beams to an acceptable accuracy. The nonlinear finite element studies showed that the ultimate strength of torsion critical CFRP Strengthened members are greatly affected by relative amount of longitudinal reinforcement, ratio of transversal and longitudinal reinforcement, pattern of distribution of longitudinal reinforcement and ratio of torsion to bending moment. The Effect of torsion to bending moment ratio (T/M) on ultimate strength of torsion is clearly observed as the reinforcement amount and distribution changes. As T/M goes from 1 and 2 the ultimate torsional strength increases in 10.73% and T/M goes from 2 and 3 the ultimate torsional strength decreases by 6%. With the increment of longitudinal Compressive reinforcement, no significant torsional strength improvement is seen. With the increment of tensile reinforcement ultimate torsional strength in general is found increased. For λ=1 the ultimate torsional strength increases there is 4% improvement in strength for λ=2 there is 4% improvement in strength .for λ=3 ultimate torsional strength decreases with the increment of tensile reinforcement. It has been also observed that an increase in transverse to longitudinal reinforcement ratio (ρt / ρL) by 75.7% causes an increase in ultimate resisting torsional moment by about 5%, 2%, 8% for torsion moment ratio of λ=1, 2 and 3 respectively. The study also showed that increasing ratio of transverse to longitudinal reinforcement improves strength only when the increment is made by proportioning relative amount of transverse to longitudinal reinforcement ratio. Moreover, during strengthening of torsion critical members, attention should be given to the amount and distribution of reinforcements and the associated bending moment as they greatly affect the torsional strength improvement