Research On Distortional Buckling Bearing Capacity Of Cold- Formed Thin-Walled Channel Steel Columns With Stiffening Members

Because of the light and high strength of steel,the bearing capacity of steel members is always controlled by the bearing capacity of global stability.The width and thickness of the plate is beneficial to the global stability,but it also brings the problem of local stability.In addition to the local buckling and global buckling,cold-formed thin-walled channel column will arise another buckling modes that is similar to local buckling——distortional buckling.The definition of distortional buckling is the system of flange and edge curl rotating around the intersection of flange and web,leading to the change of web's shape and size.So the distortional buckling will play a controlling role on the bearing capacity of the members under certain conditions.Setting stiffener on web or flange can effectively reduce the plate thickness ratio,greatly improve the local buckling critical stress of plate.And then,distortional buckling become the control mode.so the study on distortional buckling bearing capacity and applied to the design of the specification is particularly important.First of all,this paper analyzes all the standard provisions of design bearing capacity for the steel column.The methods are mainly the direct strength method(DSM)and the effective area method(EAM).The most important step for calculating bearing capacity is to draw the elastic distortional buckling stress,but the approximate analytical method used in the specification is the calculation formula being tedious and experiencing an iteration.Then,the elastic distortional buckling critical stress is obtained by using CUFSM software.According to the method of calculating the local buckling of the plate,this paper can acquire the restraint coefficient of the flange.Through multivariable regression fitting in different stiffening place and sizes,distortional buckling stress simplified formulas are fitted by MATLAB which conside different boundary conditions,different aspect ratio of the cross-section,different edge thickness ratio under the condition and so on.In the end,this paper acquire the distortional buckling damage finite element ultimate bearing capacity of cold-formed thin-walled channel steel column with V shaped stiffening ribs by using ABAQUS software.Recommended calculation formula of distortional buckling bearing capacity are fitted by MATLAB through regression fitting,numerical analysis,data comparison.