Analysis Of Mechanical Properties Of RC Beams Strengthened With Prestressed CFRP Under Natural Exposure Environment

CFRP(Carbon Fiber Reinforced Polymer)is widely used in structural reinforcement for its light weight,high strength,fatigue resistance,corrosion resistance and construction convenience.In order to explore the effect of prestressed CFRP on reinforced concrete bridges in subtropical natural exposure environments,this paper takes prestressed CFRP-strengthened RC beams as the object and studies the concrete-CFRP interface bond-slip model under natural exposure environments.The static load test under natural exposure environment is carried out.The finite element model is established by ABAQUS software,the influence of natural exposure time,prestress level and fatigue load on the fatigue performance of reinforced components is calculated,and the fatigue life is predicted.The research contents and conclusions are as follows:(1)In this paper,appropriate constitutive models of steel bar,concrete,CFRP and concrete-CFRP interface are selected,the degradation of materials and interface under fatigue load is discussed,and degradation criteria are determined.The finite element model of RC beam reinforced with prestressed CFRP is established by ABAQUS,and the appropriate calculation method is selected to simplify the calculation of cyclic load.(2)According to the experimental data,the bond-slip model of the CFRP-concrete interface under the subtropical natural exposure environment is obtained.Then,the finite element of the prestressed CFRP strengthened RC beam under the natural exposure environment is established.The static load experiment of the strengthened beam in natural exposure environment is carried out,and the experimental results are compared with the calculation results to verify the degradation trend of the concrete-CFRP interface.(3)Without considering the natural exposure environment,the finite element model is used to apply different CFRP prestress levels and fatigue loads to calculate.The results show that the increase of the prestress level can reduce the stress of the main reinforcement,reduce the structural deflection,and significantly enhance the fatigue performance of the reinforced beam.Comparing the calculated life prediction results with the experimental data,it is found that the life prediction fits the experimental data,which verifies the validity of the model.(4)Through model calculations,it is found that under fatigue load,the extension of the natural exposure time will increase the deflection of the structure,increase the stress of the main bar,accelerate the damage evolution rate of the steel bar and the concrete-CFRP interface,and shorten the fatigue life of the reinforced beam.The application of CFRP prestress can reduce the damage of the steel bar and the interface,significantly enhance the fatigue performance of the reinforced beam,and extend its fatigue life.Besides,the higher the prestress level,the longer the fatigue life,thus the application of prestress is conducive to the long-term service of CFRP reinforced beams in natural exposure environments.