Generic Element Types

In this chapter, the conventions for element names and enumerations of connectivities, edges, faces, etc. are described.

B2000++ elements are always derived from one of the generic elements, i.e. an element of a specific family, like a triangle, a tetrahedron, etc. The generic element type is not associated to any operator and is usually known to all processors dealing with elements, like the input processor, the load processor, or the element processor. Like the generic element type, the element name must be derived from the generic element name. The element naming convention sn.extension has been adopted, where s designates the shape, n the number of nodes defining the element, and extension the actual description of the element. The table below contains a list of all defined generic element types:

Table 3. Generic element type properties

Shape s N. of nodes n Description
L 2, 3 Line or wire element. Generic 1D element defined in R3.
R 2, 3 Rod element (solid mechanics) defined in R3.
B 2, 3 Beam element (solid mechanics) defined in R3.
T 3, 6 Triangular 2D element, defined in R2 and/or R3.
Q 4, 8, 9 Quadrilateral 2D element, defined in R2 and/or R3.
TE 4, 10 Tetrahedral element, defined in R3.
HE 8, 20, 27 Hexahedral element, defined in R3.
PR 6, 15 Prismatic element, defined in R3.
PY 5, 13 Pyramidal element, defined in R3.
PMASS 1 Special 0D element defined in R3.

Note that if an element is listed in the above table does not necessarily mean that the corresponding element - for a given operator - is implemented in B2000++. Examples of element names:

  • Q9.S.MITC specifies a quadrilateral solid mechanics MITC shell element with nine nodes.

  • HE8.HEAT.CONDUCTION specifies an eight node hexahedral element for solving the heat conduction equation.

The field type contains the element class pertaining to the element geometry, augmented by the number of nodes. The extension field defines the actual element type, i.e. the operator, and can be chosen freely. Data set ELEMENT-PARAMETERS contains the element name translation table.

The generic element type also uniquely defines the element coordinate system and the element node, element edge, and element face numbering conventions (see sections below). B2000++ elements are always defined in R3 space. However, certain elements are formulated in the x-y plane. By default, axisymmetric elements are defined in the x-y plane, with the x-axis being the axis of revolution.

1. Generic line (L), rod/cable (R) elements

L (line), R (rod and cable) elements define line (wire) elements without any local y- and z-axis, i.e. the elements have axisymmetric properties around the local x-axis. L elements also constitute the basis for axisymmetric two-dimensional elements.

The element local x-axis is defined by the vector r21 = p2 - p1, p2 being the coordinate of the vertex n2, and p1 the coordinate of the vertex n1. The local y- and z-axes are not defined. Note that B2000++ node indices are positive integers and they must belong to the same branch.

L2/R2 element connectivity

Figure 14. L2/R2 element connectivity

L3/R3 element connectivity

Figure 15. L3/R3 element connectivity