Subcritical deformation of the bridge structure compressed members

Abstract

An original model of subcritical deformations of compressed prismatic bars is considered. The model includes three successive stages of deformation: axial shortening without any deviation from straightness, the transitional stage (shear strain and buckling of a compressible member occurring simultaneously)and buckling of the bar of an incompressible axis. The presented model follow results of experimental investigations on metal bar stability, representing the changes of load, displacement, stress and strain components during compression process. Herein, an appearance of the column lateral displacement is explained as a result of deformation occurring when strain energy reach the maximum value. The criterion of stability loss in the form of the maximum strain energy condition is verified as well. In the article cases of stability loss are discussed for both slender columns carrying the critical load and medium slenderness columns, for which the limit state is defined by the conditions at which transition to the third deformation stage occurs. In the latter case two groups of slenderness were identified: the one for which a snap-through to a new equilibrium configuration occurs and the other for which the limit state is defined by the material instability.