| The stability is always the key problem in the area of cold-formed thin-walled steel structures. With the cold-formed steel members tending to higher strength, thinner thickness and more complex section shapes, the buckling mode of members becomes more complex. Holes change the stress distribution and reduce the plate assembly effects, therefore holes make a significant impact on its bending strength and behavior. Therefore, the stability behavior of section with holes cold-formed thin-walled steel members remains to be further research.This paper selects two kinds of cold-formed thin-walled steel members with complex edge stiffeners including C-section members and ∑-section members. And this paper investigates the stability behavior of cold-formed steel members under pure bending and non-pure bending states by test investigation and finite element.A total of 8 simply supported bending members with two types of complicated sections including channels with complex edge stiffeners and web holes (B1-section), channels with complex edge stiffeners and ∑ type web stiffeners and web holes (B2-section) were tested, for studying the effect of web holes on different sections flexural members. It contains 4 pure bending members and 4 non-pure bending members. The experimental results show that all the bending strength of B2-section specimens are higher than that of B1-section and shearing deformation was obviously observed in both B1-section and B2-section specimens. Furthermore, compared with B1-section specimens, the influence of the holes was reduced because of the setting of web stiffeners for B2-section. In the same condition, compared with the specimens without holes, the failure modes of specimens with web holes do not change, but the failure position almost appears on the cross section of holes. The bending strength of specimens with holes is lower than without holes, especially the B2-section specimens. The finite element analysis (FEA) results show good agreement with test results in terms of bending strength and buckling mode. Based on it, the stress distribution of the beams with web holes were compared with beams without web holes under the same condition by FEA. It is showed that the web holes change the stress distribution of the specimens, the positions of the max stress of B1-section and B2-section specimens are respectively near the holes and on the compression flange near loading points.Simplified calculation methods for flexural members were studied in this paper, for effective cross-section method for calculating the ultimate bearing capacity of flexural members in China was too complicated and not applicable for calculating distortional buckling bearing capacity, the sections and H/B in the United States standard and the Australia standard existed differences with the actual situation in our country. The ultimate bearing capacity of a total of 58 members were respectively calculated by direct strength method (DSM) abroad, DSM proposed in China and DSM proposed in this paper. All the calculation results above were compared with exited experiment results, as well as what were calculated by effective cross-section method. It was found good for the calculating formula proposed in this paper, and the smaller error could meet the requirement of the precision for engineering application. |
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