Design of cellular beam-columns about the major axis

Abstract

Cellular member use in buildings has increased. However, studies on the load bearing capacity of cellular columns or beam-columns are still lacking. This study aimed to examine efficiency of using EN 1993-1-1 and ANSI/AISC 360-16 to design the load bearing capacity about major axis of pin-pin supported and doubly symmetric cellular beam-columns. An examination was conducted through a parametric study of finite element (FE) analyses validated by eight tested beam-columns. The investigated parameters were steel sections, opening geometries and slenderness. For cellular columns, the design buckling strengths are less conservative than with regular columns. Differences between the design and FE strengths are from −7.2% to +6.1% for the EN method and from −11.4% to +6.3% for the AISC method. A narrow web post and a large opening diameter affect the conservatism level. Since computation of the EN reduction factor is more sensitive to opening parameters, the EN deviation is more scattered than the AISC deviation at a given slenderness. For cellular beam-columns, differences between the design and FE interaction moment at a given compression are from −4.6% to +9.0% for the EN method and from +3.5% to +15.6% for the AISC method. The design estimates move from conservative for regular beam-columns to non-conservative for cellular beam-columns. Since buckling around the opening is not considered in the AISC and EN methods, the interactions are overestimated in design estimates. The interaction factor computation in each method also affects the difference. To provide more accurate interaction results, a modified AISC interaction criterion is proposed.