Cellular and castellated members are steel Ⅰ-section members with circular or hexagonal web openings placed at regular intervals along the member's length. Compared with a member without web openings, these members have a more optimal material use in strong-axis bending. Other advantages are the savings in construction height possible by guiding service ducts through the web openings and aesthetics. However, compared with unperforated members, the resistance checks will be more complex and the fabrication cost will be higher. Depending on the boundary and loading conditions, flexural buckling about the strong axis could contribute to the failure of cellular or castellated columns or beam-columns. The corresponding critical buckling load of castellated and cellular columns is expected to be smaller than that of a similar I-section column without web openings, due to the decreased shear stiffness of the web. This is caused by the local bending and shear deformations around the openings. However, research covering this aspect is limited. In this paper, the elastic strong-axis flexural buckling behavior of castellated and cellular members will be investigated by means of a numerical parametric study. It will be shown that the existing formulations for the critical buckling load are still unsafe. Thus, a new expression for the critical buckling load will be proposed, based on an adaptation of the approach used for flexural buckling of battened columns.
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