Flange local buckling resistance and local-global buckling interaction in slender-flange welded I-section beams

Abstract

The AISC (2016) Specification idealizes the strength of slender-flange beams as the theoretical elastic plate local bucking strength. Recent research has shown that this idealization is highly conservative. There is a substantial post-buckling strength of slender flanges that is ignored in AISC (2016). As the use of slender flanges becomes more common, due to the use of higher strength steels and/or due to design optimization, there is a need to have a better characterization of their strength to improve their economy. Another important aspect not addressed in the AISC (2016) Specification’s Chapter F is the potential interaction between local and global buckling in flexural members. This effect has been studied to only a limited extent in previous research and deserves more attention to ensure the behavior of slender-flange beams is properly represented. This thesis investigates the true response of flexural members through parametric finite element analysis studies and proposes methodologies to predict the resistances. The proposed methodologies include calculations to account for the post-buckling strength of slender flanges in flexural compression. An effort is made to address local-global buckling interaction effects, where significant, via a modification of the global LTB resistance calculations. The AISC (2016) Specification procedure and the proposed methodologies are compared against the test simulation results and recommendations are provided pertaining to the simplicity of their application and the efficacy of their predictions. Through a better understanding of flange post-buckling strength and local-global interaction, this research aims to contribute towards the improvement of the Chapter F provisions of AISC Specification.