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.

The collapse modes of reinforced concrete (RC) wallboards directly affect the living space and the escape time for people during the damage of an RC shear wall structure under the impact of a strong earthquake. To summarize all the possible collapse modes of RC wallboards based on the existing theoretical studies related to the seismic collapse of RC wallboards, six corresponding indoor RC wallboard model structures were designed on a scale of 1:4. These structures were subject to a full-process low-cycle horizontal load test to emphasize the failure process and verify the theoretical collapse modes of each test model. The experimental results are consistent with the findings from relevant theoretical studies and also enrich the collapse mechanism of RC wallboards, thus providing a valuable reference for designs that can withstand seismic impacts. Graphical Abstract

Numerical analyses and theoretic analyses are presented to study the elastic buckling of H-section beam web under combined bending and shear force. Results show that the buckling stress of a single web with clamped edges gives a good agreement with the buckling stress of an H-section beam web when the local buckling of the beam is dominated by the web buckling. Based on theoretic analyses, a parametric study is conducted to simplify the calculation of buckling coefficients. The parameters involved are clarified first, and the improved equations for the buckling coefficient and buckling stress are suggested. By applying the proposed method, the web buckling slenderness ratio is defined. It is verified that the web buckling slenderness ratio has a strong correlation with the normalized ultimate strength of H-section beams when the buckling of the beams is dominated by web buckling. Finally, a design equation is proposed for the ultimate strength of H-section beams.