Structural stability is the ability of a structure to resist loading. Loss of such ability, so-called instability, is a state in which the structure is no longer in equilibrium with change in the geometry of a structure or structural component under loads. One phenomenon of structural failure led by instability is excessive structural displacements or component deformations. The underlying causes are the loss of stiffness in some particular degrees of freedom due to geometric and/or material constitutional reasons, that is, geometric and material nonlinearities.