Inelastic Buckling of Welded Monosymmetric I‐Beams

The inelastic buckling of welded monosymmetric I-beams under uniform moment has been investigated. The assumed welding residual stress is based on the so-called "tendon force concept" developed by the Cambridge group. The residual stresses are shown to be dependent on the connecting plate sizes, weld areas, and the welding process. The assumed residual stress pattern consists of a fully yielded tensile stress block of width 2c in the flange at the weld, and a constant residual compressive stress at the outer edges to maintain equilibrium. The influences of the degree of beam monosymmetry and the values of c are examined. It is shown that the inelastic buckling capacities decrease with degree of beam monosymmetry and with increasing c values. Theoretical inelastic buckling moments compared well with Fukumoto's test results, except for the very high strength grade steel. Present inelastic beam design rules in AS1250, AISC specifications, ECCS, and BS5950 are reviewed. A simple method of determining the inelastic buckling moment for welded monosymmetric I-beams is proposed.