Lateral Stability of Beams with Elastic End Restraints

Abstract

In the analysis of the lateral buckling of simply supported beams, the ends are assumed to be rigidly restrained against tip. Real supports are, of course, never perfectly rigid. This report examines the relation of the stiffness of the end axial rotation restraint to the buckling load when the stabilizing effect of an attached deck is taken into account. For the case of uniform load, it is found that as the restraint stiffness approaches zero, the buckling load also approaches zero. This has implications in the design of large roof systems where end restraint on one member is provided by the torsional rigidity of another member connected in‐line. Families of design curves are presented which show the effects of restraint stiffness, span‐depth ratio, and shear stiffness of attached roof deck. It is concluded that periodic bracing against axial rotation is essential for stability of long roof systems with several beams spliced together in‐line.