Analysis On Mechanical Behavior Of Reinforced Concrete Beams With Externally Bonded CFRP

The new technology of Carbon Fiber Reinforced Concrete Beams contains a series of theories and techniques, such as mechanics, chemistry and material and so on .In this new technology, CFRP is pasted on the surface of concrete structure with resin material in civil engineering, so that CFRP can bear load with concrete structure harmoniously. Generally, some performances of the structure reinforced with CFRP will be improved and optimized. So the new technology of Carbon Fiber Reinforced Concrete Beams will have huge social benefits and economic benefits, and wide application prospect. In the paper, a series of research is carried out, such as theoretical research, tests and the finite element nonlinear analysis. And all the research relies on the project (2003353322100) of Ministry of Communications ----<>. At last The Tao Bai NO.1 Bridge was consolidated with the foundation of the results in theoretical analysis and tests, which proved the validity in theoretical research, tests and the finite element nonlinear analysis in the paper. The bonding strength between interface of concrete and CFRP is a major control parameter in design, and it influences the results of carbon fiber reinforced concrete beams closely. Therefore, the research of bonding strength was carried out. Firstly, the author researched the strength of the interface through the stretch test. In the test, CFRP was pasted on the two sides of specimen. In the test, We observed the damage of specimen pasted by CFRP and m easured the change of strain along the stretch direction under different load conditions. The accurate measure formula of bonding strength and corresponding measure methods were put forward in theoretics, and some conclusions were sum up. By comparison with test result, which showed that this method has very high precision, it can be used to analyse the stress in the sticky layer in some actual project. Then ,the author investigated the bonding strength of sticky layer under (-25℃) through the identical test. The result shows that the performance of the bonding strength of sticky layer is very fine in low temperature. Those finds offer a reliable basis to consolidate and repair reinforced concrete beams in cold regions. Subsequently, The fatigue performance of the bonding strength of sticky layer was researched through the Fatigue---Stretch test. The result of test shows: the fatigue performance of sticky layer is choiceness, the effectual life can satisfy the requirement of bridge in endurance. The beams strengthened by CFRP embodied the excellent performance in anti-bend and anti-shear, In the second part of this paper, theoretic study of this technology was made, then the author made the bending experiment. We studied the deformation rules and damage phenomenon of this structure. On theoretical analysis, we firstly established a simplified anti-bending calculation formula. But the result of the calculation formula compared with tests is conservative. We have carried out 6 pieces of beams of anti-bending tests. Themain purpose is to investigate the change of flexural capability of the beam strengthened by CFRP, as well as some phenomenon in different stages. And we investigated the yield load, limit load, deflection changing and crack in the condition of different methods and bonding area. We analyzed the damage mechanism of the structure strengthened by CFRP and summarized the phenomenon of each stage according to the damage form. Because the CFRP reinforced concrete beams are composed of different materials, And they are much different in the property of physics and mechanics. The damage is often accompanied by material nonlinear, which makes analysis more complicated in different stage. However traditional theoretical analysis does not reflect much accurate data and information about the distribution rule in stress and strain, the development of crack and distortion, damage process and limit load. But the information is very important to realize the state of employment. So it is necessary to carry out numeric calculation under three dimensional condition for this kind of structure. This paper firstly carried out the nonlinear finite element numeric analyse and simulated 6 pieces of test beams and established a numeric model, and took series of reasonable strategy to resolve the difficulty of convergence of concrete material in calculation, and reflected the actual working environment of the structure. So we get the reliable and accurate numeric datum. The distortion rules of the beam strengthened by CFRP were explained and guided widely through this numeric model. Such as we can observe the scope of stress field and crack in different load, and preview thetest. So we can find the problems that maybe appear in actual test, So that reduce the cost and time needed by the test and make the test scheme more accurate. The author chose The Tao Bai NO.1 Bridge as the object after synthesizing theoretics and test and the finite element nonlinear analysis. Firstly, The author realized the conditions of the bridge through checking and measuring, then made the scientific scheme and technics achieve the consolidation through aborative construction. Then the bridge was checked and measured chronically, and achieved the anticipative effects, which showed the technology of CFRP strengthened concrete beams in cold regions is a secure, economic, feasible way. The strengthened project of The Tao Bai NO.1 Bridge is successful example. And the technology deserves to be popularized.