Recent advances in the dual analysis theory

The dual analysis concept, which is one of the oldest methods of measuring the discretization error of finite element models, suffered by its lack of generality in its original version. In fact, severe restrictions were imposed to the boundary conditions, excluding any mixed problem. These restrictions, related to an analysis where stiffness plays a central role, can be avoided by using the proper reference energy, which is the total complementary energy. This leads to convergence curves which are always on the same side of the exact value and whose distance measures the quality of the analyses.