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An Enhanced Design Approach for Global and Local Buckling Resistance of Welded Box Section Columns

The construction industry is witnessing an increased utilization of steel elements due to their effectiveness and durability, with the ability to fabricate lightweight sections having high bearing capacity. Welded box‐section is one of those elements that gain more attention as it is easy to fabricate and has limited stability issues. Buckling is considered one of the major issues that hinder the ability of the steel box‐section to attain its full capacity. The buckling problem for this type of column can be classified into three major types: overall buckling, local buckling, and interacting buckling. Different research activities studied the overall and the local buckling stabilities of box‐section columns, while only a limited number of researchers studied the interaction stability that compromises both types of buckling. Additionally, the available design standards do not account for the nonlinear nature of combining these two buckling types and only use a simple approach to account for their combined effect, leading to a considerably conservative estimation of the buckling capacity. The current research utilizes a FEM‐based design approach to account for the combined nonlinear effect through the utilization of geometrical and material nonlinear analysis (GMNIA) by the creation of a numerical model of square welded box‐section columns, applying a nonlinear material model, an improved combination of local and global imperfections developed by the authors during previous research as well as the residual stresses. The numerical model is validated against experimental tests available in the literature. Then, it is used to carry out a numerical parametric study with a significant number of tests to build a numerical database that can be used to develop an enhanced design approach for the interactive buckling resistance of box‐sections columns under pure compression. The new approach is based on a reliable and accurate numerical model considering an improved combination of the local and global geometric imperfections and residual stresses, which gives more accurate results than the previous model published in international literature. The paper also describes the way of the imperfection combinations to be applied. The new design approach also considers the interaction of the global and local reduction factors depending on the global and local slenderness ratio leading to accurate buckling resistance.