Material Properties And Local Stability Of Corroded Cold-formed Thin-walled C-section Steel Axial Compression Columns

Cold-formed thin-walled steel structural members are widely used in practical engineering due to its advantages of light weight,high strength,convenient and rapid construction,high industrialization and good seismic performance.However,because of its thin wall thickness,the cold-formed thin-walled steel structural members are easy to be damaged due to instability,and the stability problem has become a hot research topic of cold-formed thin-walled steel structural members.In addition,cold-formed thin-walled steel structural members,which has been in corrosive environment for a long time,is difficult to avoid corrosion through traditional protective and structural measures.Corrosion increases width-thickness ratio of the cold-formed thin-walled steel structural members and degrades mechanical properties of materials,the stability problem becomes more prominent.Based on this,this paper firstly studied the degradation law of mechanical properties of the corroded cold-formed thin-walled c-section steel,and then studied local stability of the corroded cold-formed thin-walled c-section steel columns subjected to axial compression by means of experimental research,numerical simulation and theoretical analysis.The main contents are as follows:(1)Stress-strain curves of flat specimens and corner specimens was obtained by conducting monotonic tensile tests on 13 flat specimens and 12 corner specimens.The relationship between mechanical properties of the corroded cold-formed thin-walled c-section steel and degree of corrosion were studied.In addition,the differences between mechanical properties of flat specimens and mechanical properties of corner specimens due to cold-work hardening effect were compared.Finally,the constitutive model of the corroded cold-formed thin-walled steel was established.(2)Load-axial displacement curves,load-transverse displacement curves and load-strain curves of the corroded specimens were obtained through local stability tests of six cold-formed thin-walled steel columns with different degrees of corrosion.Critical buckling load of the axial compression columns was determined by strain reversal method.The effects of corrosion on local buckling failure mode,local buckling critical load,ultimate bearing capacity,buckling stress and ultimate stress of the cold-formed thin-walled c-section steel columns subjected to axial compression were investigated.The degradation law of local stability of the corroded cold-formed thin-walled c-section steel columns subjected to axial compression was revealed.(3)The finite element software ABAQUS was used to perform finite element analysis on the corroded cold-formed thin-walled c-section steel columns subjected to axial compression,and adopting eigenvalue buckling analysis and nonlinear buckling analysis,a finite element model of the corroded cold-formed c-section columns subjected to axial compression was established by considering reduction of section thickness and degradation of material mechanical properties.The correctness of the model was verified by comparing with experimental results.On this basis,the effects of different types and degrees of corrosion on local stability of the cold-formed thin-walled c-section steel columns subjected to axial compression were investigated.(4)The effects of different types of corrosion on local stability of the cold-formed thin-walled steel columns subjected to axial compression were compared by means of finite element method and theoretical analysis.The calculation methods of local buckling critical stress and ultimate stress of corroded cold-formed c-section steel columns under subjected to axial compression were established.