Analysis Of Remaining Bearing Capacity And Prediction Of Life Of Steel-concrete Composite Beams Under Corrosion And Fatigue

In recent years,with the rapid economic development,more and more bridges have appeared in the public eye.As a unique part of the bridge,the steel-concrete composite bridge is composed of concrete,steel beams and shear connectors.Concrete has the advantages of compression resistance and steel beam tensile strength.It also has shorter construction time,lighter weight than concrete beams,and good structural ductility,so it is more and more widely used.However,in the long-term operation process,due to the degradation of material properties,there is a widespread problem of reduced bearing capacity,which causes great safety hazards,and may even lead to catastrophic consequences such as bridge collapse.Therefore,it is very important to evaluate the bearing capacity and reliability of steel-concrete composite bridges.This paper uses ABAQUS modeling,adding vehicle fatigue loads on the basis of different levels of chloride ion corrosion and different levels of chloride ion corrosion,and calculates and analyzes the remaining bearing capacity of steel-concrete composite beams.At the same time,the time-varying reliability theory is used to calculate the reliability index of the steel-concrete composite beam,combined with the lowest target reliability index to predict its life.The research content is as follows:(1)Firstly,analyze the factors affecting the performance degradation of steel-concrete composite beams,and select reasonable corrosion degradation models of concrete,steel beams,and studs,as well as the interface bond-slip model between steel-concrete composite beams,and use finite element ABAQUS to establish The refined model of steel-concrete composite beams is used for static symmetrical loading of steel-concrete composite beams under different levels of chloride ion corrosion,and their ultimate bearing capacity is calculated and analyzed.The results show that the ultimate bearing capacity of steel-concrete composite beams decreases rapidly in the early stage and slows down in the later stage.In addition,in 40 years,the ultimate bearing capacity of composite beams has decreased by 5%,and the interface slip has increased by 12.4%;in 70 years,the ultimate bearing capacity has dropped by nearly 10%,and the interface slip has increased by 17.9%.The degradation is very obvious.(2)Add fatigue load on the basis of chloride ion corrosion,select the fatigue degradation model of concrete,steel beam,stud and the corresponding interface bond-slip model;analyze and calculate the bearing capacity of steel-concrete composite beam through ABAQUS.The results showed that under the dual effects of corrosion and fatigue,the ultimate bearing capacity dropped by more than 10% in 50 years;the amount of interface slip increased exponentially with time.In 70 years,the maximum slip of the composite beam reached2.158 mm,an increase of 20.2%.The performance degradation of composite beams is becoming more and more obvious.(3)ABAQUS is used to calculate the load effect of composite beams,and the degeneration model of influencing factors of composite beams is used to calculate and analyze the flexural bearing capacity of steel-concrete composite beams.According to the JC method program written by MATLAB,the reliability of the steel-concrete composite beam is analyzed.The results show that the reliability index of the bridge decreases relatively slowly in the early stage,and the reliability index also decreases sharply in the later stage due to the accumulation of fatigue effects.And according to the target reliability index combined with the principle of 85% guarantee rate,the remaining life of the composite beam is predicted.