Lateral Stability of Glued Laminated Beams

The lateral buckling of glued laminated beams is governed by the parameter Ld/b², not by d/b as is assumed by many building codes. Simple equations are derived for the critical buckling stress and the allowable design stress for rectangular timber beams with various support and load conditions. The concept of short, intermediate, and long beams is needed to account for buckling in the inelastic and elastic ranges. Laboratory tests show that the recommended formulas for design provide a factor of safety ranging from 2.5 for short beams to 3.0 for long beams. The resistance to lateral buckling is influenced by the bracing that is present. Diaphragm action of a roof deck will prevent lateral buckling in many cases.