Statically indeterminate

[1][2] Based on Newton's laws of motion, the equilibrium equations available for a two-dimensional body are:[2] In the beam construction on the right, the four unknown reactions are VA, VB, VC, and HA.

To solve statically indeterminate systems (determine the various moment and force reactions within it), one considers the material properties and compatibility in deformations.

In order to distinguish between this and the situation when a system under equilibrium is perturbed and becomes unstable, it is preferable to use the phrase partly constrained here.

It indicates the possibility of self-stress (stress in the absence of an external load) that may be induced by mechanical or thermal action.

Practically, a structure is called 'statically overdetermined' when it comprises more mechanical constraints – like walls, columns or bolts – than absolutely necessary for stability.