Mixed Dimensional Coupling for Efficient Structural Finite Element Analyses

Many practical finite element models contain long slender regions and areas where the thickness is small in relation to the other dimensions. The slender regions are best modelled using 1D beam elements, while shell or plate type elements should be used to represent any areas consisting of thin walls. These reduced element types are much more efficient than using full 3D continuum elements (which may be ill-conditioned) and hence are often used. However, in most practical models, both long slender regions and thin regions are usually bounded by areas containing complex geometry, loading or boundary conditions which require a full 3D analysis model. In order to avail of the reduced element types, it is important to have some scheme available for coupling them in an analysis. Such a technique is discussed here. To avoid stress disturbances at the interface, coupling is carried out in a way that conforms with the theory of elasticity.