Prediction for elastic local buckling stress and ultimate strength of H-section beam

The local stability of the H-section beam is essentially determined by the width-thickness ratios of flange and web. Current design codes provide width-thickness ratio limits to classify sectional ranks regarding local buckling. However, the local buckling stress and ultimate strength cannot be accurately predicted using the width-thickness ratio alone. This study aims to develop highly accurate calculation methods for both elastic local buckling stress and ultimate strength. We present a simplified theoretical method for elastic flange local buckling that considers rotational restraints and torsional restraints provided by the web. It is confirmed that the buckling stress of a single flange obtained by theoretical analysis corresponds closely with the results of the finite element analyses when local buckling is controlled by flange local buckling. Besides, based on the theoretical analysis, important parameters are determined. Through a parametric study, a model for calculating the local buckling stress of the H-section beam covering all cases of local buckling types is suggested. It is demonstrated that the local buckling slenderness ratio based on the improved calculation method has a strong correlation with the experimental normalized ultimate strength of the H-section beam. Finally, we propose a design formula that outperforms conventional methods in predicting the normalized ultimate strength.