Behaviors Of Reinforced Concrete Beams Strengthened By Using Composite Fiberglass Reinforced Cloth

It is a new and effective strengthening technology to use the composite fiberglass reinforced cloth (CFRC) to strengthen the reinforced concrete structures, which is widely applicable in structural engineering. In this thesis, the behaviors of the reinforced concrete (RC) beams strengthened by using the CFRC were investigated experimentally and theoretically. The analytical methods for the relevant bonding, bending, shearing and fatigue behaviors of the CFRC strengthened RC beams have been established. The investigation was focused on as follows:(1) The static bonding behaviors of the CFRC strengthened RC beams under the condition of tension, double-shearing and bending-tension. The influences of the concrete strength grade, thickness of CFRC and bonding length on the bonding strength, bonding effective length and load carry capacity were analyzed. The distribution regulation of CFRC tension strain and averaging shear stress were discussed in detail. The effective bonding length and CFRC maximum tension strains were obtained and the formulas of bonding load carry capacity for resistant shear were presented. The incomplete bonding behaviors and the cyclic bonding behaviors were studied to give the calculating formula of ultimate load carry capacity under the condition of incomplete bonding.(2) The bending performance and strengthening effects of the CFRC strengthened RC beams. The influences of CFRC on the load carry capacity, stiffness and cracks distribution of the strengthened RC beams were analyzed by considering the ratio of reinforcing bar and CFGC thickness. The CFRC design strain value and strengthening design formulas for resistant shear were presented.(3) The shearing performance and strengthening effects of the CFRC strengthened RC beams. The influences of bonding mode and shear span ratio on the strengthening effect for resistant shear was investigated. Based on these results, the CFRC design strain value and strengthening design formulas for resistant shear were presented.(4) The simulation of loading procedures on the CFRC strengthened RC beams by using finite element model. The key simulation skills of finite element modeling for the CFRC strengthened RC beams were established. The simulation results were agreed well with the test results. (5) The fatigue behaviors of the CFRC strengthened RC beams. Based on the experimental results, the changing laws of deflection in the middle span and the fatigue cracks of the strengthened RC beams were analyzed. The relationships of the deflection and cracks with the applied load and cyclic numbers, and the expression of reducing coefficients of the fatigue bending stiffness have been established. The fatigue strengthening effect of the CFRC strengthened RC beams was analyzed.