In this report, the inelastic local buckling of webs of beams under combined bending and thrust were investigated. The theoretical solution was derived based on the plastic deformation theory under the assumption of elastic perfectly plastic material. In order to study the validity of the theoretical solution, experiments were carried out for two types of specimens, one of which was built up I-section and other was T-section in conjunction with plate. As the result of comparing the numerical calculations with experiments, the following important informations were obtained. 1. The results of theoretical calculations for critical strains showed comparatively good agreement with experiments. 2. The effect of the cross sectional configurations to the critical strain of webs and the effect of the thrust to the critical depth and thickness ratio of web were clarified. 3. According to the theoretical and experimental results, critical depth and thickness ratio of web is larger especially in lower strain range than that indicated by G.Haaijer.
