Shear buckling strengths of web-posts in a castellated steel beam with hexagonal web openings

• Shear buckling strength of web-post Vcr was investigated through a free body.
• Vcr was obtained by a verified finite element model.
• Method for shear buckling coefficient k was proposed using reverse analysis.
• Vcr of a web-post employing proposed k agreed well with simulation results.

Shear buckling behaviors of web-post in a Castellated Steel Beam (CSB) with hexagonal web openings under vertical shear were investigated using finite element method. Through treating the upper part of the web-post as a free body under horizontal shear force, whose shear buckling strength can be calculated by the thin-plate shear buckling theory, design equations for the vertical shear buckling strength of the web-post were proposed. Parameters that affected the vertical shear buckling strength of the web-post were studied, which were the opening height to web thickness ratio h0/tw, the web-post width to web thickness ratio e/tw, the web height of Tee-section above the opening to the web thickness hf/tw, the web thickness tw and the incline angle of the opening edge α. After obtaining the vertical shear buckling strength of a CSB through finite element model, the shear buckling coefficient k can be obtained through inverse analysis. Research results showed that k decreased non-linearly with the increase in e/tw and hf/tw and it increased linearly with the increase in α and h0/tw. Practical calculating method for k was proposed based on parameter analysis results. The vertical shear buckling strength of the web-post calculated using the proposed shear buckling coefficient k agreed well with that obtained from the finite element simulation. For the proposed method was based on the elastic buckling of the web-post, it overestimated the shear buckling strength when the web-post buckled in the elastic–plastic state.