Review article

The article considers a new effect, namely, spontaneous bending (due to the vanishingly small disturbance) of an inelastic column when it is centrally compressed by a force that is less than critical. Earlier, no attention was paid to this effect. The problem is discussed on the example of a simply supported column of rectangular cross section. At a certain level of the force applied to the column curved due to spontaneous bending, the force increment causes the moment increment of an indefinite value. This force level is considered to be the critical one. Its calculation, which does not take into account the non-monotonic increase in stresses during the column deformation, gives the critical force exactly equal to the tangent modulus one.