ABSTRACT
A large number of structures can suffer a change in their deformation during loading. This change is usually accompanied by a major or minor reduction of stiffness that does not depend on material yielding. Such a phenomenon occurs because the equilibrium configurations of the structure become unstable during loading and the structure snaps or buckles, seeking new stable equilibrium states. It is also possible that to reach these new states, the structure suffers such high strains as to fail. The various instabilities occurring in structural systems under the action of conservative loads can be subdivided into three different groups: Buckling with stable branching; buckling with unstable branching; and snapping-through. The existence of various equilibrium branches that depart from the critical state implies that a symmetric and stable equilibrium bifurcation occurs at buckling. Euler’s pioneering investigations on the “Elastica” were the first studies on the equilibrium bifurcation of elastic structures.
