About Functional Structures

Functional structures are a class of very large models such as ship hulls.

The principles of finite element analysis for functional structures are unchanged from any other model. However, the element size defaults are quite different from those of smaller models.

The element size used for a typical model would produce a mesh of far too great a density for analysis of a functional structure. Instead of a mesh size of a few millimeters or centimeters, functional structures might have mesh sizes closer to a meter.

Functional structures are available only when you have the appropriate role.

This page discusses:

Finite Elements and Functional Structures

Functional structures require a larger scale mesh than smaller models.

Simulation of a large structural assembly requires specialized techniques to generate an appropriate mesh.

When a functional structure model is converted into a mesh, the panels and profiles are converted to shells (Shell Section_Panel Name-Plate Name) and beams (Beam Section_Panel Name-Stiffener Name). The app creates shell section properties for each panel. If the panel has stiffeners, the app also creates coating 1D mesh parts. A panel might also consist of multiple plates, each with different thicknesses or materials. In these cases additional shell section properties are created for each change of thickness or material.

Similarly, the app creates beam section properties for all profiles (stiffeners). If a profile has different sections or materials, the app creates additional beam section properties. The beam profiles for stiffeners use the ProfileType parameter (if one is defined) or the section name from the original structure to create the correct profile shape.

Mesh Constraints in Functional Structures

Mesh constraints define points or lines that must lie between mesh elements, not within a single element.

When meshing a functional structure, several types of features typically result in mesh constraints. For example, the following are line (edge) constraints:

  • Panel-to-panel connections: edges along which panels are joined.
  • Panel-to-stiffener connections: edges that define the stiffener location along a panel.
  • Panel seams: edges within a panel, defined when a panel is divided into plates that can have different thickness or material properties.

Likewise, point constraints are created for the following:

  • Panel-to-panel connections: point at which panels are joined, if they connect at one point.
  • Panel-to-beam connections: points at which panels and beams are joined.
  • Beam-to-beam connections: points at which beams are joined.

Multiple constraints close together can create poor elements in that mesh region. For example, if a seam is close to a connection between panels—or between a panel and a stiffener—small elements are created in the space between the two edge types. However, you can specify that constraints within a specified distance (the Constraint Condensation Threshold) are treated as one. This typically improves the local mesh quality in areas with multiple constraints.