The paper refers to stability of compressed prismatic steel beam columns in the range of plastic deformation. The rods are characterized by slenderness ratio of lambda < lambda(H), where lambda(H) = pi root R-H, R-H is proportional limit of the steel. The original experimental tests as well as tests carried out by Z. Wasiutynski is described in the paper. The analysis of experimental results is made with respect to the proposed by author formulas determining both the static and geometric parameters of beam columns as well as the energy and the work of external forces of the critical state of axially compressed bar. The research is complemented by calculation of safety factors, which due to proposed by author analysis is lower than that proposed by Polish standard PN-90/B-03200, on static analysis and design of steel structures. It was stated experimentally that with decreasing of the slenderness ratio of compressed bars the work of compression (L-s(c)) increases quickly whereas the work of bending (L-zg) decreases. It is stated that the axis of failure forces (P-n) remain within core of a cross-section, what indicate that very short bars, which can be loaded by compressed forces of the value near yield point (R-e), do not buckle.
