FEM-based design for global and local buckling interaction of welded box-section columns

Interaction behavior of global (flexural) and local buckling is a widely researched, but currently not solved problem in the design of slender welded box-section columns. In the current recommendations, two design methods are available: (i) analytical design approaches, which might consider the coupled stability problem by adjustment of the global or local slenderness ratio of the column, and (ii) finite element method (FEM) based-design covering imperfection combinations in the numerical model. Despite numerous previous experimental and numerical results, there is no reliable analytical or FEM-based design approach to determine the buckling resistance. This research topic gets special importance by the increased application of high strength steel structures (yield strength larger than 500 MPa), which might have larger slenderness than columns using normal strength steel, increasing the need for the appropriate design for the interacting stability problem. The current research program focuses on these phenomena for both normal and high strength steel structures separately.

The executed research program investigates the FEM-based design approach, emphasizing the model imperfections and their combination to achieve appropriate buckling resistance. By the application of equivalent geometric imperfections covering different stability issues the effect of residual stresses will be duplicated leading to conservative buckling resistances. The current paper investigates the imperfection sensitivity of the coupled stability problem and gives design proposal on the imperfection magnitudes to be applied in numerical models for FEM-based design approach.

Learning Objectives:
Using appropriate values for the equivalent geometric imperfections, the effect of residual stresses on the buckling resistance can be considered accurately.

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