Study On Mechanical Behavior Of Concrete-filled Steel Tube Columns With Local Circumferential Corrosion Under Eccentric Compression

When concrete-filled steel tube members are used in corrosive environment,the outer steel pipe will inevitably suffer from natural corrosion.the wall thickness and material properties of the steel pipe will be weakened,resulting in the decline of the bearing capacity of the whole member and the safety of the structure.The continuous deterioration of corrosion will threaten personal safety and cause serious engineering accidents.Concrete-filled steel tube structures used in marine environment are easy to form serious local circumferential corrosion in the splash area of seawater spray.In order to evaluate the bearing capacity of concrete-filled steel tube eccentric compression members subjected to local circumferential corrosion and discuss the effects of corrosion rate and eccentricity on their mechanical properties,relevant experimental research,finite element simulation and theoretical analysis were carried out.In this paper,14 concrete-filled steel tube specimens were designed and fabricated,including 12 specimens with local circumferential corrosion and 2 non-corrosion control specimens.By comparing the failure process,failure mode,load-axial displacement curve,load-lateral deflection curve,deflection development curve,load-strain curve and section strain distribution of each specimen,the different effects of corrosion rate and eccentricity on the mechanical properties of locally circumferential corroded concrete-filled steel tube eccentric compression members with different section forms were discussed.The test results show that the concrete-filled circular steel tube specimens are finally damaged due to the annular bulging at both ends of the corrosion zone on the compression side,while the concrete-filled square steel tube specimens are finally damaged due to the interconnected local bulging in the middle of the corrosion zone on the compression side and side.The bearing capacity of the specimen decreases with the increase of corrosion rate and eccentricity.The ductility of the specimen decreases with the increase of corrosion rate and increases with the increase of eccentricity.The finite element models were established by ABAQUS.The test results and simulation results were compared from three aspects: failure mode,load-lateral deflection curve and bearing capacity to verify their correctness and applicability.Based on the finite element models,the mechanism of eccentrically loaded concrete-filled circular steel tube and concrete-filled square steel tube members with local circumferential corrosion were analyzed respectively,and their mechanical properties were analyzed from the aspects of failure mode,load distribution,stress distribution and interaction.Based on the finite element models,the parameter analysis of the bearing capacity was carried out,mainly including: concrete strength,steel strength,steel ratio,slenderness ratio,eccentricity and corrosion rate.The results show that the reduction coefficient of bearing capacity increases with the increase of concrete strength,and decreases with the increase of steel strength,steel ratio,slenderness ratio,eccentricity and corrosion rate.Based on the parameter analysis,the calculation formula of bearing capacity reduction coefficient was proposed through nonlinear regression.According to the calculation formula of eccentric bearing capacity in Chinese and American codes,the calculated value of bearing capacity of each specimen was compared with the test value.The results show that the calculated value is close to the test value,and the overall error is less than 10%.Compared with Chinese code,American code is relatively more conservative.