Buckling approximations for inelastic beams

Hand methods of calculating buckling loads of inelastic moment gradient beams are developed. An inelastic parameter, the stiffness modification factor, j, is used to estimate equivalent uniform tangent modulus rigidities for partially yielded simply supported beams. From this is developed a buckling moment equation. For laterally continuous beams, a step-by-step procedure which allows for interaction between adjacent segments is proposed. The structure is reduced to a critical subassemblage of beam segments. The stiffness modification factor is used to quantify segment end interaction and an effective length factor, k, is found for the critical segment. The buckling moment equation is used to estimate the beam capacity. A worked example and comparisons with theoretical and experimental results show that the proposals are accurate and simple to apply.