Design methods of high strength steel welded H-sections under compression accounting for local-global buckling

For medium-length steel columns with high width-to-thickness ratio, the local-global interactive buckling may be the dominant failure mode. The existing design methods deal with the interactive buckling through combining the Effective Width Method (EWM) with column buckling curves, but they are demonstrated to provide inac-curate resistance predictions for high strength steel (HSS) columns. This paper presented a theoretical and nu-merical study for the buckling strength of the HSS welded H-section columns. A theoretical method was proposed to calculate the elastic local buckling stress based on the plate buckling theory. A finite element (FE) model with proper consideration of the initial imperfections was developed and validated by the existing experimental re-sults. Then, the Continuous Strength Method (CSM) was refined for the prediction of the local buckling capacity of HSS H-section stub columns. Based on parametric studies, the method in current design codes was modified to consider the local-global interactive buckling. Furthermore, a new method based on the relative slenderness approach was proposed for the axial compressive capacity prediction to explicitly consider the interactive effect between the local and global buckling. Accuracy of the proposed design method was evaluated by the experi-mental and numerical data, showing a better accuracy than the current codes. Based on reliability analysis, partial safety factor was determined for the proposed method to meet the target reliability index.