Fully automatic p-adaptive hybrid-trefftz displacement elements.

This paper reports on the implementation details of a fully automatic p-adaptive procedure to select the approximationbases of the displacement model of the hybrid-Trefftz finite element formulation. The formulation allows for the directapproximation and enrichment of two independent fields, the displacements in the domain and the surface forces onthe element boundaries. By controlling the strain energy of the system for a prescribed finite element mesh, the padaptivealgorithm uses the nonconformity and nonequilibrium error minimization criterion to identify the boundary anddomain regions where the degree of the surface force and displacement bases should be increased or alternatively in whichelements the kinematic indeterminacy number of the domain bases should be enriched. Numerical results demonstrate theefficiency of the algorithmand the feasibility of carrying out automatic p-adaptive enrichment in 2D elastostastic analyses.