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This paper reports an experimental study about the mechanical properties of square rigid flange used in steel transmission poles. Static tests were carried out on six specimens of square flange in two groups, and finite element models were employed to simulate the test loading procedure. It is indicated that good agreement exists between FEA results and experimental results. According to the current standards, the square flange and ribs can be safely designed with the method of circular flange design, but it is unreliable to use the method for bolts under combined tension and bending stresses. Actually, overstress of bolts is caused by the asymmetrical distribution of flange stiffness. In this paper, it is recommended to use the comer cut flange and ribs placed along the upper and lower sides to reduce the non-uniformly distributed stress. Finally, the axis of bolts in second row is suggested to be the rotation axis under the bending load, and the maximum stress of bolts is close to the experimental results, which is 20% larger than the value according to the current standards. [ABSTRACT FROM AUTHOR]

A total of eight 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. The specimens included four pure bending members and four non-pure bending members. The experimental results show that all the bending strength of B2-section specimens are higher than those of B1-section and shear deformation can be obviously observed in both B1-section and B2-section specimens. Furthermore, compared with B1-section specimens, the influence of web holes is reduced because of the setting of web stiffeners for B2-section. On the same condition, compared with the specimens without holes, the failure modes of specimens with web boles do not change, but the failure position always appears on the cross section of holes. The bending strength of specimens with boles is lower, 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. The stress distribution of the beams with web holes were compared with beams without web holes under the same condition by FEA. It is shown that the web holes change the stress distribution of the specimens. The positions of the maximum stress of BI-section and B2-section specimens are near the holes and on the compression flange near loading points respectively. [ABSTRACT FROM AUTHOR]