Cross section records

These records describe the cross section models.

Record syntax

CrossSectType num (in) [set (in)]

The order of the records is arbitrary and the cross section number is given by num. Unlike nodes and elements, the numbering must start at one and end at n, where n is the number of records.

Parameter common to all cross sections

[set (in)]

Number of an element set (see Set records) to which this cross section assigns itself. This is the usual way of binding a cross section — and through it a material — to elements, and it is why an element record often carries neither crossSect nor mat.

All cross section properties are understood to be defined in the local coordinate system of the element.

Integral cross section with constant properties

The integral type of cross section model. For some problems, 3D ones in particular, the volume and the cross section dimensions follow from the element geometry, in which case some or all of these parameters may be omitted; consult the Element Library Manual for the properties an individual element requires.

Record syntax

SimpleCS num (in) [material (in)] [set (in)] [thick (rn)] [width (rn)] [area (rn)] [iy (rn)] [iz (rn)] [ik (rn)] [beamshearcoeff (rn)] [shearareay (rn)] [shearareaz (rn)] [drillstiffness (rn)] [reldrillstiffness (rn)] [drilltype (in)] [directorx (rn)] [directory (rn)] [directorz (rn)]

Parameters

[material (in)]

Number of the material record for the bulk material.

[thick (rn)], [width (rn)]

Cross section thickness and width.

[area (rn)]

Cross section area.

[iy (rn)], [iz (rn)]

Inertia moments about the local y and z axes.

[ik (rn)]

Saint-Venant torsional constant.

[beamshearcoeff (rn)]

Shear correction factor. Alternatively give the equivalent shear areas shearareay and shearareaz.

[shearareay (rn)], [shearareaz (rn)]

Equivalent shear areas in the y and z directions.

[drillstiffness (rn)], [reldrillstiffness (rn)], [drilltype (in)]

Artificial stiffness added for drilling DOFs: an absolute penalty term, a relative penalty term, and the type of the added stiffness. Relevant for shell elements with drilling degrees of freedom.

[directorx (rn)], [directory (rn)], [directorz (rn)]

Components of the director vector, for shell formulations that need one.

Integral cross section with variable properties

The same integral cross section model, but with the individual properties given as arbitrary functions of the global coordinates x, y, z. As with SimpleCS, for some problems the volume and cross section dimensions follow from the element geometry and many parameters may be omitted.

Record syntax

VariableCS num (in) [material (in)] [set (in)] [thick (expr)] [width (expr)] [area (expr)] [iy (expr)] [iz (expr)] [ik (expr)] [shearareay (expr)] [shearareaz (expr)]

The parameters have the same meaning as in Integral cross section with constant properties, but each takes an expression (see Attribute types) rather than a number. shearareay and shearareaz determine the shear area required by beam and plate elements.

Layered cross section

The layered cross section model, based on the geometrical hypothesis that cross sections remain planar after deformation.

Elements using this cross section model must implement the layered cross section extension; see the Element Library Manual.

Record syntax

LayeredCS num (in) nLayers (in) LayerMaterials (ia) Thicks (ra) Widths (ra) [set (in)] [midSurf (rn)] [nintegrationpoints (in)] [layerintegrationpoints (ia)] [beamshearcoeffxz (rn)] [interfacematerials (ia)] [rotations (ra)] [initiationlimits (ra)]

Parameters

nLayers (in)

Number of layers.

LayerMaterials (ia)

Material number for each layer.

Thicks (ra), Widths (ra)

Thickness and width of each layer.

[midSurf (rn)]

Position of the mid surface, given as its distance from the bottom of the cross section; normal and moment forces are computed with respect to it. By default it lies at the average thickness position.

[nintegrationpoints (in)]

Number of integration points per layer. Default is one. The Gauss integration rule is used within each layer.

[layerintegrationpoints (ia)]

Number of integration points for each individual layer; its size should equal the number of layers. This overrides nintegrationpoints.

[beamshearcoeffxz (rn)]

Shear correction factor for 2D beam sections, controlling the effective shear area used to evaluate the shear force. Default 1.0.

[interfacematerials (ia)]

Material numbers of the interfaces between the layers, for delamination modelling.

[rotations (ra)]

Rotation of each layer about the cross section normal, for laminates whose plies have different fibre orientations.

[initiationlimits (ra)]

Limits controlling the initiation of interface failure.

Fibered cross section

A cross section represented as a set of rectangular fibers. It rests on the geometrical hypothesis that cross sections remain planar after deformation, and is the 3D generalization of the layered approach for beams.

Important

The geometry of the cross section is determined from the fiber dimensions and fiber positions, all given in the local coordinate system of the beam, that is in the yz plane.

Record syntax

FiberedCS num (in) nfibers (in) fibermaterials (ia) thicks (ra) widths (ra) thick (rn) width (rn) fiberycentrecoords (ra) fiberzcentrecoords (ra) [set (in)]

Parameters

nfibers (in)

Number of fibers forming the overall cross section.

fibermaterials (ia)

Material model number for each fiber. The material model specified at element level has no meaning in this case.

thicks (ra), widths (ra)

Thickness and width of each fiber.

thick (rn), width (rn)

Overall thickness and width of the cross section.

fiberycentrecoords (ra), fiberzcentrecoords (ra)

y and z coordinates of the centre of each fiber.

Warping cross section

Cross section for free warping analysis; see Free warping analysis.

Record syntax

WarpingCS num (in) WarpingNode (in) [set (in)]

Parameters

WarpingNode (in)

Number of the external node carrying the prescribed boundary condition that corresponds to the relative twist of the warping cross section.

Lattice cross section

Note

Part of the lattice module; compile with USE_LM.

Cross section for the 3D lattice elements lattice3d and lattice3dnl, and for the 2D lattice element lattice2d.

Record syntax

LatticeCS num (in) material (in) [set (in)] [shape (in)] [radius (rn)] [area (rn)] [thickness (rn)] [iy (rn)] [iz (rn)] [ik (rn)] [shearcoeff (rn)] [shearareay (rn)] [shearareaz (rn)] [nlayers (in)]

Parameters

material (in)

Number of the material record.

[shape (in)]

How the section properties are obtained. Default 0.

0

A general polygon or facet built from the element vertex coordinates (polycoords).

1

A circle, from radius.

2

A rectangle, from four vertices.

3

A property-defined section, given directly with no geometry.

For the geometric shapes 0, 1 and 2 the properties are computed from the geometry, and any individual property may be overridden by supplying its value here.

[radius (rn)]

Radius, used by shape 1.

[area (rn)]

Cross section area. Mandatory for the property-defined section (shape 3).

[thickness (rn)]

Cross section thickness.

[iy (rn)], [iz (rn)]

Second moments of area about the local y and z axes.

[ik (rn)]

Saint-Venant torsional constant.

[shearcoeff (rn)]

Shear correction factor. Alternatively give shearareay and shearareaz.

[shearareay (rn)], [shearareaz (rn)]

Equivalent shear areas.

[nlayers (in)]

Number of through-thickness layers of a shell. Shell mode is activated by the element’s shellnormal; the default is a single integration point at the centroid.

For the property-defined section (shape 3) the element represents a two-node frame member — rod, beam and so on. area is then mandatory and the remaining properties optional; the transverse axes are oriented by the element’s zaxis, and the integration point position along the element by its s parameter. See the Element Library Manual.

For lattice2d only shape 1 is evaluated. It gives a circular frame section with \(A=\pi r^2\), \(I=\pi r^4/4\) and shear area \(0.9A\); the overrides area, iz and shearareay apply. For all other shapes, lattice2d uses the rectangle defined by its own width and thick parameters.

Other cross section types

SimpleTransportCS

Cross section for transport problems. Takes mat (in), [thickness (rn)] and [area (rn)].

FluidCS

Cross section for fluid dynamic problems. Takes mat (in).

InterfaceCS

Cross section for structural interface elements. Takes material (in) and [thickness (rn)].

EmptyCS, DummyCS

Placeholder cross sections carrying no properties, used where an element requires a cross section but none of its properties are needed.