Review article

In the rod under consideration, shear stress depends both on the shearing force in the cross section and on the bending moment. The Tymoshenko beam theory does not take this aspect into account. This article investigates the problem basing on the improved theory for shear accounting. It is shown that in the case of a rod of constant cross-section, a direct implication of the Timoshenko model is the Haringx equation connecting the critical force that takes shear into account, with the critical Euler force. However, even in the case of constant cross section, this equation is valid only for some simple beam supports.