Study On The Effect Of Local Corrosion On The Mechanical Properties Of Concrete-filled Circular Steel Tube Compression-bending Members

With the rapid development of CFST arch bridges in our country’s highway and railway transportation industry,many CFST arch bridges have appeared diseases.Steel corrosion has seriously threatened the durability of bridges.Therefore,it is necessary to carry out research on the effect of corrosion on the mechanical properties of CFST structures.Considering that the corrosion area of arch rib is mainly concentrated at the arch foot,the connection between the rib arch and the suspender,and the rib vault,the design considers the stress state of the arch rib during the service process of the CFST arch bridge.Three types of local corrosion(local Corrosion areas are located at the end,middle,and both ends of the specimen).The experimental study of CFST members under combination between compression and bending is conducted,and the following conclusions are obtained:(1)A total of 45 locally corroded circular steel tube concrete members under eccentric loading were tests.The test parameters included corrosion volume,corrosion area and corrosion location.The whole process analysis was carried out on the three types of local corrosion specimens,respectively.The test results show that the failure modes of the three types of local corrosion specimens are all belonging to instability failures.For the specimens with the local corrosion at one end and the local corrosion at both ends,the bending failure mainly occurs at the junction of the corroded area and the uncorroded area;for the parts with the local corrosion in the middle,the bending failure occurs in the middle of the local corrosion area.With the increase of the corrosion volume,the ultimate load bearing capacity of the three types of local corrosion specimens all show a downward trend;when the corrosion volume is the same,the ultimate load bearing capacity of the parts of the two types of local corrosion is higher than that of the other two types.(2)On the basis of experimental research,using the finite element software ABAQUS,three-dimensional finite element numerical analysis model of the test specimens were established.Starting from the load(N)-lateral deflection(u_m)relationship curve and ultimate load bearing capacity,the finite element calculation results and the test results were compared and analyzed to verify the correctness and rationality of the FEM models,which provides reference for follow-up experimental study and finite element calculation.Based on the finite element calculation results,in-depth research of the three types of local corrosion of circular CFST specimens were analyzed in the process of load contribution between the steel tube and concrete,the lateral restraint force of the steel tube on the core concrete,and the changes in the stress distribution layout.(3)Based on the test results and the calculation results of the finite element model,a expression between locally corroded concrete-filled steel tubes and ordinary concrete-filled steel tubes under eccentric compression was proposed.The calculation results of the formula were in good agreement with the test results,which confirmed the accuracy of the formula;through the parameter analysis of different steel strength grades,concrete strength,eccentricity,steel tube wall thickness and slenderness ratio of eccentrically compressed steel tube members,the applicability of the formula was verified.This formula can be used to calculate the bearing capacity of CFST eccentric compression members with different forms of corrosion.