Editing Statically indeterminate (section)

== Statical determinacy ==
Descriptively, a statically determinate structure can be defined as a structure where, if it is possible to find internal actions in equilibrium with external loads, those internal actions are unique. The structure has no possible states of self-stress, i.e. internal forces in equilibrium with zero external loads are not possible. Statical indeterminacy, however, is the existence of a non-trivial (non-zero) solution to the [[Homogeneous system of linear equations|homogeneous system]] of equilibrium equations. It indicates the possibility of self-stress (stress in the absence of an external load) that may be induced by mechanical or thermal action.

Mathematically, this requires a [[stiffness matrix]] to have full rank.

A statically indeterminate structure can only be analyzed by including further information like material properties and deflections. Numerically, this can be achieved by using matrix structural analyses, [[finite element method]] (FEM) or the [[moment distribution method]] ([[Hardy Cross]]) .

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