Simplified Calculation Method For Shear Buckling Strength Of Web-post In A Castellated Steel Beam Based Sub-model

The Castellated Steel Beam(CSB)can be made through cutting an H-section steel beam in a zig-zag pattern along the web and then re-welding the two parts together at the convex area.The strength to weight ratio of the beam is increased without additional usage of steel.At the same time,the story height of the building can be reduced by installing the service pipelines in web openings.Existences of web openings break the continuity of beam web.Compared with the solid web steel beam,the CSB may fail in new modes,like the buckling of the web-post under vertical shear force.Practical calculating method for k in elastic part and elastic-plastic part was proposed based on parameter analysis results,respectively.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.The sub-model selected the upper part of the web-post under horizontal shear to represent the whole web-post under vertical shear.Proper boundary conditions were applied to the sub-model to assure its behaviors were identical to those of the whole web-post.Parameters that might affect the vertical shear buckling strength of the whole 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 hexagonal opening edge a.After obtaining the vertical shear buckling strength of a CSB through finite element model,the shear buckling coefficient k in elastic part and in elastic-plastic part can be obtained through inverse analysis,respectively.The elastic 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 buckles in the elastic-plastic state.Through introducing a safety factor of 1.2,the precision of the proposed method was increased.The elastic-plastic 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 and test results.And it was more precise than those obtained from EC3 based on the strut model.