Papers by Keyword: Carbon Fiber Laminate (CFL)

Abstract: This paper study the effects of stress amplitude on the fatigue performance of reinforced concrete (RC) beams strengthened with carbon fibre laminate (CFL). A total of 15 spcimens were tested under three point bending. Three load levels over 60% bending capacity of the strengthened beams with a stress ratio of 0.1 were applied to three groups of five specimens, respectively. The stress amplitudes of groups 2 and 3 are 10% and 15% larger than group 1, respectively. The loads and deflections during the tests were recorded. The fatigue stiffness of the strengthened RC beams with variable stress amplitude was discussed. The experimental results show that the rates of the bending stiffness deterioration of the retrofitted beams, which increase with the load level, under constant fatigue loading are smaller than those under variable fatigue loading.

Abstract: Based on experimental research and calculation theory of flexural bearing capacity, a method for calculating the ultimate load bearing of normal section member strengthened with prestressed CFL is proposed. Static load experimental results of two beams show that when prestress level is 20%, the cracking load and yield load of RC beams strengthened with prestressed CFL are 37.5% and 39.3% respectively. It is larger than that of RC beam strengthened with nonprestressed CFL.

Abstract: Deem test results from the low reversed cyclic loading quasi-static test with 2 RC columns as the basic information of secant stiffness damage of the reference column and take use of the TMS instrument in the test to artificially make the damage percentage of secant stiffness of the RC column as 33%, 50% and 66%, 6 damaged columns in total; reinforce the 6 damaged columns and 2 undamaged ones under the same conditions with AFL, through quasi-static contrast test. Test results show that it is able to effectively boost horizontal ultimate bearing capacity and ductility deformability of the RC columns with AFL for reinforcement; besides, there is a linear function relationship between horizontal ultimate bearing capacity, target ductility factor, and damage percentage of secant stiffness.

Abstract: Externally bonded reinforcing technique with fiber reinforced polymer (FRP) has been widely used in civil engineering. The performance of the interface between FRP and concrete is one of the key factors affecting the behavior of the strengthened structures. This paper presents a detailed study on the bond-slip mechanism between carbon fiber laminate (CFL) and concrete based on double-shear tests. 8 specimens with different bonded length and width of CFL were tested under static loading. Strain gauges along the CFL face and displacement sensor were used to measure longitudinal strains and slip of the interface. The bond-slip constitutive relation of the interface between CFL and concrete was analyzed with the testing results. Compared with four different bond-slip models, a shear stress-slip model was proposed based on the experimental data.

Abstract: In this letter, an alternating-direction reduced finite-difference time-domain (ADI-R-FDTD) method is presents. It is proven that the divergence relationship of electric-field and magnetic-field is non-zero even in charge-free regions, when the electric-field and magnetic-field are calculated with alternating-direction finite-difference time-domain (ADI-FDTD) method in 3 dimensions case, and the expression of the divergence relationship is derived. Based on the non-zero divergence relationship, the ADI-FDTD method is combined with the reduced finite-difference time-domain (R-FDTD) method. In the proposed method, the memory requirement of ADI-R-FDTD is reduced by1/12 of the memory requirement of ADI-FDTD averagely in 3D case. The formulation is presented and the accuracy and efficiency of the proposed method is verified by comparing the results with the conventional results.

Abstract: Bonding prestressed CFL to strengthen reinforced RC structures can improve the bending capability of structures and the working efficient of CFL. Base on the fatigue experiments of 4 RC beams strengthened by prestressed CFL, the present paper analyzes the fatigue properties of prestressed CFL reinforced RC beams. Comparing with the experimental results of strengthened RC beams without prestress, it can be concluded that the prestressed technology can improve the reinforcing effect and fatigue lives.

Abstract: The interfacial bonding property between carbon fiber laminate (CFL) and concrete is a key issue in the application of RC beams strengthened with CFL. In this paper, fracture mechanics method is used to develop a calculation formula of stress intensity factor for the CFL-concrete interfacial crack. In combination with a series of tests, the interfacial fracture toughness is discussed, and the influencing factors and process of the intermediate crack-induced debonding (IC debonding) are also analyzed. The tests results show that IC debonding is generally induced by the flexural or flexural-shear cracks in the bottom of RC beams around the mid-span, and develop along the interface towards the end of the beam. A method to determine IC debonding derived from theoretic analysis and the tests results demonstrates that the interfacial failure can be effectively avoided by limiting CFL strain in the range of the debonding strain.