Study On The Performance Of Partially Prestressed Concrete Beams Strengthened With FRP Sheets

As most of the bridges in our country were built before the 1990 s,most of them already can't satisfy the requirement of heavy traffic due to the influence of constant physical and chemical corrosion,collision and other external factors.However,the cost both of money and time are high to build new bridges.Therefor fiber reinforcement is a economic and effective method to improve the bearing capacity and can also prolonging the service life of the bridges.In this paper,the influence of carbon fiber reinforced polymer(CFRP),aramid carbon fiber reinforced polymer(AFRP)and hybrid carbon-aramid fiber reinforced polymer(C/AFRP)on the mechanical properties of bridge structures was studied.C/AFRP reinforcement is a new type of technology.At present,there are few researches on the reinforcement technology in the world.In this paper,we conducted in-depth experimental research and theoretical analysis.The main research contents and conclusions are as follows:1.The bending test of PPC beams was investigated with 4 test beams.The test data obtained cracking load,yield load and ultimate load,and destruction mode,beam deflection,strain,ductility and crack changes of test beam under static condition are analyzed.The test results indicated that fiber reinforced method can effectively improve the bearing capacity of the beam,reduce the deflection of the beam,and dispersed the tension zone of concrete tensile stress,inhibit the development of cracks;the ductility and flexural performance of reinforced concrete beams strengthened with C/AFRP is better than the others.2.The constant amplitude fatigue test of PPC beams was investigated with 8 test beams,the fatigue life,material strain amplitude,midspan deflection and crack variation law of the test beam under fatigue load condition are analyzed.The test results indicated that there are more than 2 million times of the fatigue life of the beams strengthened with FRP,deformation rate significantly reduced,effectively reduce the fatigue cumulative damage and better performance;anti-fatigue properties of C/AFRP reinforced beam is superior to the other reinforced beams,which has a great significance in studying new reinforcement technology with new fiber sheet.3.Based on the fatigue test,the fatigue cumulative damage analysis of the test beam iscarried out,and the physical relationship between the damage amount and fatigue life is established.Using the Miner linear cumulative damage theory to analyze the test beam,pre-established the curve between the maximum strain and damage variable and calculate the damage threshold of test beams;based on the stiffness attenuation law,the stiffness and the damage quantity are introduced to analyze the cumulative damage of the test beam and the prediction of fatigue life was made.The calculation results are almost identical with the measured data.Through the research of test beams based on attenuation law of stiffness degradation,the failure criterion of flexural rigidity was acquired.These theoretical researches can provide reference for the timing of engineering reinforcement,the prediction of fatigue life and the detection of test beam.