Study On Fatigue Life Prediction Of Reinforced Concrete Beams Strengthened With Intelligent CFRP Plate

In recent years,new composite materials,such as carbon fiber,have been widely used in the reinforcement of bridge structures,and some achievements have been made in the research of the fatigue performance test.After strengthening the reinforced concrete bridge,many factors such as the composition of the bridge structure,the mechanical properties and the environmental conditions of the original concrete have all changed.If we continue to use the original method to evaluate the service life of the bridge after reinforcement,it is unreasonable.If the long-term monitoring performance can be given to the reinforcement material,it can truly reflect the information of the bearing capacity of the structure during service,and make use of the fatigue life assessment so as to bring the assessment results closer to the actual conditions.This is of great significance to the prediction of remaining service life and maintenance optimization of existing service bridges.With the support of National Natural Science Foundation of China,this paper takes the concrete simple beam bridge as the research object.The smart composites will be invented based on fiber reinforced polymer composite and optical fiber bragg grating sensing technology.The fatigue test of reinforced concrete beams is carried out.(1)The fatigue test of reinforced concrete beams strengthened with intelligent CFRP plates under different stress levels is carried out by single point loading method.Finally,the crack development of the test beams under cyclic loading,the deformation of the mid span deflection,the failure form,and the fatigue test results of steel bar,carbon fiber plate and concrete strain are also obtained.And the test results and fatigue phenomena are analyzed accordingly.(2)On the basis of fatigue test,the fatigue performance of concrete beams strengthened with CFRP plate under three point bending constant amplitude cyclic loading is studied.The change trend of stress amplitude and overall residual stiffness of reinforced concrete beams strengthened with CFRP plates with load cycles is emphatically studied.Referring to the standard requirements,based on the stress level,the stress amplitude of steel bar and the remaining flexural rigidity,the fatigue life of reinforced components is studied,and the empirical formula of fatigue life is fitted by test data.(3)Through the analysis of fatigue performance and fatigue life of reinforced concrete beams strengthened with intelligent CFRP plates,the fatigue life prediction method of concrete beams strengthened with intelligent CFRP is deduced based on the nominal stress amplitude of steel bar and the plane cross-section assumption.Through the example,it is found that the fatigue life predicted by this method is less than the fatigue failure cycle number obtained from the actual test,and it is safe.So it can be used to guide the actual engineering to predict the fatigue life of the reinforcement structure.