  We prove the accuracy of a mixed finite element method for bending dominated
shells in which a major part of the membrane/shear strain is reduced, to free
up membrane/shear locking. When no part of the membrane/shear strain is
reduced, the method becomes a consistent discontinuous Galerkin method that is
proven accurate for membrane/shear dominated shells and intermediate shells.
The two methods can be coded in a single program by using a parameter. We
propose a procedure of numerically detecting the asymptotic behavior of a
shell, choosing the parameter value in the method, and producing accurate
approximation for a given shell problem. The method uses piecewise linear
functions to approximate all the variables. The analysis is carried out for
shells whose middle surfaces have the most general geometries, which shows that
the method has the optimal order of accuracy for general shells and the
accuracy is robust with respect to the shell thickness. In the particular case
that the geometrical coefficients of the shell middle surface are piecewise
constants the accuracy is uniform with respect to the shell thickness.
