The Research On The Whole Stability Of Axially Loaded Compression Members Of Opening Cold-formed Thin-walled Steel Sections With Stiffer Plates

The cold-formed thin-wall steel is used more and more in the construction industry, in which , the opening cold-formed thin-wall steel, as we call, because processing of it is easier than those in close section,is accepted and used widely . As we notice that the section shape of this kind of steel is single-axile symmetry, when it is compressed under axially load, it will lose stability with bending and torsion before its failure pressure, which result in the unfully usage of the capacity.By the analysis of its theory, it is pointed that during the process of axially load, the opening cold-formed thin-wall steel is wrapped easily by its opening direction, which decreases the bearing performances of the member as a whole. In this paper ,the tests are used in which some of the stiffer plates are arranged regularly in its opening direction. The stiffer plates has the ability to obstruct the wrapping deformation in opening section,thus the the bearing performances of the member as a whole will be increased.In this paper ,in which both the theorial calculation and the experiment are used, the finite element method (FEM) software of ANSYS is used. Based on the criterion of the ultimate limit states, the calculative method ,the opening cold-formed thin-wall steel with the stiffer plates, are founded out, In this method , the comprehensive effect both the residual stress and the initial defects is considered.In the Technical Code of The Cold-formed Thin-wall Steel Structures (GB50018-2002), which is used in China, unfortunately , it only provides the two circumstances of the stiffer-plate , that is for those to have the stiffer-plate and those not to have one. But it is regretly not to point out clearly the amount of the stiffer-plate. In this paper the relationship of the slenderness ratio of the steel member is founded and the reasonly arrangement of the stiffer-plate is expounded in order to the purpose of the economy and increasing dramatically the bearing performances. The method will be some of value in the engineering practice and the complement and perfection of the code.