International Research Seminar on "Rhe theory and application of finite element methods"
July26-August 10, 1973
University of Calgary
[en] Finite elements ; equilibrium models ; diffusive elements
[en] Equiliobrium models are characterized by an internal stress field in equilibrium and surface tractions that should obey the diffusivity requirement of reciprocity with adjacent elements at the interfaces. Thepaper discusses the construction of stiffness matices for such elements and the difficulties associated with the presence of mechanisms. The use of first order or second order stress functions is presented together with the possibility of solving the final equations by the force method through a direct flexibility method. Three methods are presented for getting rid of thre machanisms: the classical superelement technique, a method based on the discretization of rotational equilibrium and quasi-diffusivity.