Elastic Buckling of a Column Under Varying Axial Force

When a truss or open-web steel joist is used as a frame member, parts of the bottom chord near the ends carry compressive forces and adequate bracing must be provided to prevent lateral buckling of the chord. The compression in the chord varies from panel to panel; the problem is to determine the buckling load factor for a given loading and assumed location of the bracing point. Although the problem can be solved exactly, a simple procedure is given herein which may be used in the design office for rapid, hand computation of the buckling load factor in the elastic range.