Lateral buckling of eccentrically braced RHS columns

Rectangular hollow section (RHS) is widely used as columns of agricultural greenhouse constructions. To enhance the resistance of these columns against the out-of-plane buckling failure, the bracing system is frequently adopted, typically composed of the bracing spans containing a two-layer x-brace at intervals of a number of spans and a horizontal bar connecting the mid-height sections of all columns of the same row. The horizontal bar provides the lateral brace to the columns between two adjacent bracing spans. Due to ease of installation and existence of glass at the outer face, the horizontal bar is usually connected to the inner face of the columns at the edges of the construction (side columns) using the overlapped joints, leading to the side columns being eccentrically braced by the horizontal bar. The present paper carried out an investigation into behavior of the eccentrically braced RHS columns, including the buckling load, failure mode, bracing eccentricity, bracing stiffness and the relationships between. Simple approximations of good accuracy are also provided for the normalized critical bracing eccentricity and buckling load, with which the hand-calculation method is only necessary in practical design. A worked example is given for side columns in greenhouse constructions following the procedure presented in this study.

► The upper bound buckling load of eccentrically braced RHS columns is Py2.
► The bracing eccentricity and stiffness are the key factors for braced RHS columns.
► The imperfection and multi-column system are considered in threshold bracing stiffness.
► The simple approximations are proposed for the hand-calculation design.