Study On The Stability Of Cold-formed Built-up Stiffened Cruciform Members Subjected To Axial Load

The built-up cold-formed thin-walled steel members are increasingly widely used.The new type stiffened cruciform members made of four lipped angle steel are often used as columns.However,the torsional buckling of this type of members was not investigated sufficiently,and the buckling mode of this type of members is complex which subject to axial load.To comprehensively understand the performance of this kind of members under axial load,experimental and numerical investigation are carried out.Considering the effects of torsional buckling and splitting effect on the axial compression performance,design method of the built-up cold-formed stiffened cruciform members which are subjected to axial load is suggested.Specific work is as follows:(1)Consider the effects of slenderness ratio,side width to thickness ratio,curling width to thickness ratio and bolt spacing,16 pieces of built-up stiffened cruciform members were designed and subjected to axial compression test using orthogonal test method.And,the failure process,failure mode,load-strain curve,load axial displacement curve,load-span mid-deflection curve,load-torsion angle curve and ultimate load of the specimen were obtained.(2)The finite element analysis software ABAQUS was used for numerical simulation of the test specimen.On the basis of the comparison and verification of the finite element model from the aspects of failure mode,load-axial displacement curve,ultimate load and test results,the effects of slenderness ratio,width-to-thickness ratio,curling width-tothickness ratio,bolt spacing and other factors on the axial compression performance of members were known.Besides,with the comparison of the results of the finite element model of the overall member,the effect of splitting effect on the axial compression performance of built-up stiffened cruciform members was researched.(3)According to the effective width method in the “Technical specifications for cold-formed and thin-walled steel structures”(GB50018-2002)for the calculation of the axial bearing capacity of built-up stiffened cruciform members,the calculation results and the test results were compared.The reasons for the difference in the calculation results of the ultimate bearing capacity of this type of members in Chinese codes is that the effects of torsional buckling and splitting effect on the axial compression performance of the members are not considered.On this basis,a calculation method for the ultimate load of built-up stiffened cruciform members subjected to axial load was proposed.