Analysis of Mixed Finite Elements for Elasticity. II. Weak stress symmetry

We consider mixed finite element methods for linear elasticity where the symmetry of the stress tensor is weakly enforced. Both an a priori and a posteriori error analysis are given for several known families of methods that are uniformly valid in the incompressible limit. Based on the Prager-Singe hypercircle principle, an a posteriori estimate with explicitly known constants is derived. The results are verified by numerical examples.