The Research Of Stiffness Of Concrete Beams Strengthened With Carbon Fiber Based On Secondary Load

As the years passed there will be cracks, aging and other problems in reinforced concrete structures.The bearing capacity and stiffness will reduce, and there must be certain security risks in normal use. Sometimes the existing building can not be rebuilt. In order to continue to use the existing strucrure safely, reduce the costs required for reconstruction and time, we must carry on the reinforcing reinforcement. Carbon fiber is one of new reinforcement materials which is widely used in reinforcement engineering in recent years. At present there are many studies about carbon fiber reinforced concrete structures,but research on the stiffness of CFRP reinforced concrete beams with different initial load and different layers of CFRP is little. While the existing concrete structures already withstand a certain load before reinforcing.So sdudies about the stiffness of CFRP reinforced concrete beams with initial load has important significance.In this paper, based on the experimental studies of many domestic and foreign scholars,21concrete beams are simulated and analyzed using finite element software ANSYS.the influences of initial load size and layers of CFRP to reinforcement effect are also analyzed.The results show that:the yield load, ultimate bearing capacity and the stiffness of CFRP reinforced beams are improved to different extent.With the increase of CFRP layers, the improvement of ultimate bearing capacity and the stiffness became more remarkable.And with the increase of initial load, the maximum deflection increase and the improvement of ultimate bearing capacity and the stiffness minishes. The bigger the initial load, the smaller bearing capacity increase, especially for stiffness of reinforced baams. So,in conclusion, CFRP reinforced concrete beams have very good reinforcement effect, particularly for the improvement of ultimate bearing capacity. But the initial load influence reinforcement effect. Therefore, correctly judge different load history before reinforcing construction is very important.The simulated data in this research shows that:CFRP reinforced concrete beams is also according with flat section assumption, and reinforced beams with initial load has the problem of CFRP strain delay.Through the analysis of experimental data and ANSYS simulation data,the formula to calculate the stiffness of reinforced beams deduced by classmates Ge Chao is corrected.The corrected formula has a fairly high algebraic accuracy which is validated with simulated data.and the formula can satisfy the design and construction requirements, which have a certain reference value.