Constrained Lateral Buckling of I‐Beam Gable Frames

An important failure mode of I‐beam gable frames is lateral buckling of the compressed inside flange near the corner of the frame. The magnitude of the buckling load depends on the support provided by the joint at the corner. The outside flange is restrained from translation out of the plane of the frame, whereby the buckling mode is described solely in terms of the angle of rotation of the beams. For the common joint type with a corner plate connecting the flanges a kinematic condition relating the angle of rotation and its derivative for the two beams is derived. A simple beam‐type finite element formulation suitable for design computations is given, and some numerical examples are presented. The support provided by the corner depends on the relative buckling stiffness of the two members. Examples indicate that reasonable approximations to the buckling load can be obtained by the present design procedures using two separate beam calculations. However, if the two beams have approximately the same buckling load, the simplified beam procedure may be unconservative.