Bearing Capacity Analysis and Design Method of Q690 High Strength Steel Round Pipe in Bending

[Purposes] Most of the current research focuses on high strength steel axial compression members, and the cross-section forms are mostly welded H-shaped sections and box sections. However, there are few studies focusing on the mechanical properties of Q690 high strength steel pipe under bending, especially the different failure characteristics and their boundaries of flexural members with changing slenderness ratio have not been systematically studied. [Methods] Numerical analyses were carried out for the mechanical properties and instability mechanism of Q690 high strength steel tubular bending members. The effects of initial imperfections such as residual stress, pre-buckling deformation, and material plasticity on stable bearing capacity were investigated, and different failure characteristics were defined when slenderness ratio was changed. [Findings] According to on the analysis results, the bending bearing capacity curves of Q690 high strength steel pipe are obtained by the method in the European Code for Design of Steel Structures EN1993-1-6(2007), and the influence parameters of the bearing capacity curves at different stages are determined. The calculation formulae of the ultimate bearing capacity of members at different stages are proposed. This work provides scientific basis for the revision of steel structure design standard and high strength steel design standard in the future, and also provides theoretical support and design basis for the wide use of Q690 high strength steel round tube members in wind power tower, large span transmission tower, and substation framework.