Stability Of Cold-formed C-section Steel Beam-column Members Under Axial Load And Minor Axis Bending

The stability of cold-formed thin-walled steel structures is a key factor for the engineering design. There are three common failure modes, local buckling, distortional buckling and lateral-torsional buckling. In the process of historical research results translate into specifications, there are two methods to calculate the bearing capacity of the cold-formed thin-walled steel, Eiffective Section Method(ESM) and Direct Strength Method(DSM).Most national regulation provision adopt ESM, but it cannot be applied to distortional buckling. DSM get more attention in recent years for its simple calculation and extensive applicability, promotion of DSM will be gradually extended and and its development is imperative. As the research about DSM mainly confined to axial compression and bending, DSM is not suitable for the complex loading and boundary conditions, the research is still in the primary stage, the relevant specification do not adopt this method, it is a very important issues for us to enrich the calculation method based on DSM.Based on thin-wall channels under the axial force and the minor axis bending, the above problems are investigated by test and theoretical analysis in this paper, which give great helps to a profound understanding of its stability behavior and the relevant calculation method, the paper mainly completed the following works:① Investigating the buckling performance for cold-formed thin-wall channels by tests. There are a total of 40 members. The properties of stability are obtained by changing different web width, lip width, member thickness, length and eccentric types. It is indicated from results of the experiment: members under negative eccentrically load failed in local buckling and members under positive eccentrically load failed in distortional buckling; members under negative eccentric load show higher strength after buckling than members which is under positive eccentric load; the eccentric direction directly determines the failure mode, eccentricity has a significant influence on the ultimate capacity of members.② A number of finite element parametric analysis were performed for cold-formed thin-walled channels under eccentric compressive load. First of all, conclusion of experimental data proofs the rationality of the finite element models. Then a series of variable parameters simulation analysis were carried out. These parameters include the web width, flange width, lip width, thickness, length, eccentric direction and eccentricity. The analysis results show that thickness has greater influence on the buckling mode and ultimate bearing capacity than the web, flange and lip; Length within a certain range has little influence on the buckling mode and bearing capacity; the eccentric direction is directly determines the failure mode, ultimate capacity decreases as the eccentricity increases.③ A axial force and bending moment equation are introduced to get new DSM formulas by taking the original DSM axial compression/bending formulas as standard and basing on the results of test and parameters analysis in this paper. The rationality and validity of the proposed formula is verified by the comparing of the calculation results with the experimental data and the finite element analysis results.