Editing Virtual work (section)

==Alternative forms==
A specialization of the principle of virtual forces is the [[unit dummy force method]], which is very useful for computing displacements in structural systems. According to [[D'Alembert's principle]], inclusion of inertial forces as additional body forces will give the virtual work equation applicable to dynamical systems. More generalized principles can be derived by:

* allowing variations of all quantities.
* using [[Lagrange multipliers]] to impose boundary conditions and/or to relax the conditions specified in the two states.

These are described in some of the references.

Among the many [[energy principles in structural mechanics]], the virtual work principle deserves a special place due to its generality that leads to powerful applications in [[structural analysis]], [[solid mechanics]], and [[finite element method in structural mechanics]].