| The prestressed CFRP(Carbon Fiber Reinforced Plastic)reinforcement technology is favored by the engineering community because of its good reinforcement effect.However,due to insufficient deformation ability of the reinforcement member before failure,the ductility coefficient cannot meet the current design specifications(based on the characteristics of the elastic-plastic force member).The requirements of ductile components therefore limit the engineering applications.This study mainly considers that prestressed CFRP reinforced members have the characteristics of enhanced elastoplastic model.Although the deformation capacity after the steel bars yield is insufficient,it has high bearing potential.Measuring the safety reserves after yielding only by the deformation safety reserves is one-sided.Therefore,it is necessary to find a reasonable safety reserves index for such components to evaluate,and improve the original reinforcement method to solve the problem that the damage is not obvious and improve its safety reservess.The main research contents and results of this paper are as follows:(1)Analysis of the influence of various factors on the stress characteristics and safety reserves index of prestressed CFRPIn order to study the flexural reinforcement effect of prestressed CFRP,a set of prestressed CFRP plates were tested for bending and strengthening RC beams.The experimental research shows that the bearing capacity and stiffness of the reinforced members are obviously improved,and the crack development is limited,but the ductility is significantly lower than that of the unreinforced beams.To investigate the influence of various factors on the safety reservess of the reinforced members,it is reasonable to verify the finite element model.On the basis of sex,three sets of models were designed from three angles: reinforcement ratio,fiber ratio and prestress.The analysis shows that the influence of the reinforcement ratio on the safety reserves index is closely related to the failure mode.When the failure mode is changed from carbon fiber sheet breaking to concrete crushing,the safety reserves is improved;Too high or too low fiber ratio will cause the problem of serious shortage of safety reserves of the reinforcing members;The effect of increasing the prestress on the ultimate load is not very obvious,and the excessive prestress may cause insufficient safety reservess.(2)Establish a pre-stress CFRP bending reinforcement safety reserves prediction modelIn order to realize the quantitative prediction of safety reserve index,the calculation formula of safety reserve of bearing capacity is deduced.Based on the hypothesis of double broken line,the prediction model of safety reserve index K＿eq after calculating the wholeprocess deflection of reinforced members and equivalent bearing capacity is deduced.The deduced results are in good agreement with the simulation results,which shows that the prediction model of safety reserve index has high application value.(3)Experimental and theoretical study on the method of bending reinforcement based on the concept of "warning wire"For the problem that the reinforcement scheme may not meet the safety reserves requirements,this study proposes an improvement measure based on the concept of“warning wire”,which divides the fiber material into the bearing part and the early warning part respectively,and the “early warning wire” part is relatively small with a large prestressing force to achieve the "warning wire" fracture before the yielding of the steel bar so that gives obvious warning information,and the component can continue to bear,and the safety reserves index of the equivalent bearing capacity of the component can be improved. |
