Comparison of the Known Hypotheses of Lateral Buckling in the Elastic-Plastic States of Thin-Walled Semi-Slender Columns

Stability of structures, as known, is a challenging issue, especially in critical engineering, i.e., in designing structures which in a wrong design process could cause a catastrophe. The avoidance of possible stability troubles is mandatory. In this study, the simplifications and hypotheses of loss of stability by lateral buckling in elastic-plastic states of semi-slender columns axially compressed by force are presented. The Tetmajer-Jasiski's and Johnson-Ostenfeld's simplifications as well as Engesser-Krmn-Shanley's, Ylinen, Bezina, Pearson-Bleich-Vol'mir's and author's approximated hypotheses are analysed. The graphs of surface functions of the compressing critical stress cr depending on the ratios = a/t or = R/t and = L/t are presented as the theoretical examples of thinwalled cylindrical and square columns made of steel R35. In order to compare the results of the author's approximated hypothesis, i.e., the modified Engesser-Krmn-Shanley's hypothesis with others simplifications and hypotheses are shown in adequately ranges for elasticplastic states as the graphs of the functions cr().