Experimental Comparison of the Known Hypotheses of the Lateral Buckling for Semi-Slender Pinned Columns

The paper presents the comparison of experimental results obtained from tests on semi-slender columns with pinned ends made of steel R35 to simplifications and hypotheses of loss of stability by lateral buckling in elastic-plastic states of columns axially compressed by force. The Tetmajer-Jasiński’s and Johnson-Ostenfeld’s simplifications, as well as the hypotheses given by Engesser and Kármán and Shanley, Ylinen, Březina, Pearson and Bleich and Vol’mir and the author's one approximated, are analyzed. The graphs of surface functions of critical compressive stress σ_cr(A, L*t) depending on a cross-section area and length times thickness product are presented as the theoretical examples of thin-walled cylindrical and square columns made of steel R35. In order to compare the experimental results with other simplifications and hypotheses are shown in the adequate ranges for elastic-plastic states as the graphs of the functions of critical compressive stress depending on slenderness ratio σ_cr(λ).