Discrete structural models, as a basis for evolving a new design methodology, created the need for considering structural configuration as a variable. Existing energy methods and variational principles do not provide analysis link between pairs of structural configurations, whereas Principle of Quasi Work addresses this need. This is proved for discrete structural models by adapting Tellegen’s theorem used in topologically similar electrical networks. Several forms of the basic theorem and derivatives of Principle of Quasi Work are deduced. Its import on structural analysis is examined. Illustrative example of nonlinear structural system is included. Examples of linear and nonlinear structural systems are included.