Requirements for Lateral Bracing of Columns with Two Spans

Abstract

Lateral bracing requirements for two‐span elastic columns are examined. The braces are represented by elastic translational springs. The columns have pinned supports at the base, an internal brace at an arbitrary point, and either a pinned support or a brace at the top, where an axial load is applied. They may be perfect or may have an initial deflection. The effects of the span lengths, bracing stiffnesses, and initial deflection shapes are studied. For perfect columns, the bracing stiffness required for a given critical load is determined. For imperfect columns, the required bracing stiffness corresponding to a given deflection under a given load is investigated. Based on the results, design guidelines for bracing stiffness and strength are recommended. The rules depend on the end conditions and the location of the internal brace. For imperfect columns, they also depend on the initial deflection and the allowable size of the deflection of the column under a specified compressive load.