Experimental And Theoretical Study Of Elastic Critical Local Buckling Stress Of The Cold-formed Steel Bending Members

At present, the Effective Width Method (EWM) is widely used to design cold-formed steel members at home and abroad. This approach only considers local buckling of individual element and neglects the interaction of the adjacent plates. The effective width of a plate is related to stress gradient, which makes the EWM considerately difficult especially for the sections with complex stiffeners. T.Pekoz B.Schafer(both come from Cornell University ) and G. Hancock (comes from Australia) develop a new method named Direct Strength Method (DSM) in the last ten years. This method doesn't use effective width. It uses gross section and its geometric properties. Direct Strength Method is based on the elastic local buckling of the section and its key point is to determine the local buckling stress f_ol of the section.Based on the published materials of elastic interactive buckling, the experimental and theoretical study of critical elastic local buckling stress f_ol of the complete section of hat-shaped purlin made from Q235 and 550MPa high strength cold-formed steel have been completed. The experimental result confirmed that the finite strip method can be used to solve the critical elastic local buckling moment or stress. Several kinds of factor s that affect the critical elastic local buckling were analysed. Among these factors, the ratio of the web to the flange named b₂/b₁ is the major factor. A simplified formula for the elastic local interactive buckling coefficient K was presented.