# Splitting elements graphically

1D and 2D elements can be split. Various methods are available for doing this, as described below.

Generally the attributes of the existing element are adopted by the new elements and the local directions of the new elements generally align with those of the existing. However, the element releases in the new elements are established to result in releases at only the existing positions; a release at end one of the existing element results in a release at end one of only the element at that position.

Note that bizarre modifications to the topology of the model will occur if coincident nodes are collapsed during the operation and the coincidence tolerance is too coarse.

# Splitting 1D elements

1D elements can be split using the Sculpt > 1D element operations > Split 1D elements menu command.

The option is given to split loads and replace references to original elements with references to new elements. Note that the splitting of loads does not occur where a load is applied to an element because that element is included in a saved list or grid plane that is referred to by the loading record rather than being referred to directly in the loading record list. In this circumstance references to the old element in the saved list or grid plane are replaced by references to the new split elements.

Example: Element 12 has a linearly varying load applied to it and is split. If the element list for the beam load record is 12 then that load will be split correctly, whereas if the element list is #1 and element 12 is included in saved list 1 then that load will not be split. However, in list 1 reference to element 12 will be replaced by the numbers of the new split elements, resulting in a saw-tooth load pattern along the new elements.

A warning is given when this circumstance arises (though it’s always worth checking). The Delete displayed loading command may be helpful when rectifying such problems.

The procedure is as follows:

Set the cursor mode to Select elements.
Select the elements to be split. Elements that are not 1D will be ignored by this operation.
Give the Split 1D elements command.
Specify how the elements are to be split in the Split 1D elements dialog box.

# Splitting 2D elements

The 2D element splitting options described below are sometimes used as a means of generating a 2D element mesh. Note that an option for generating 2D element meshes is also available in GSA.

In each of the 2D element splitting options the shape of the existing element is interpolated recognising the shape function of the element. Thus splitting a Quad 8 element, which is a quadratic element, results in new elements fitting the implied quadratic surface.

# Splitting quad elements

Quad 4 and Quad 8 elements can be split into an equal number of elements along opposite edges using the Sculpt > 2D element operations > Split quad elements menu command. The procedure is as follows.

Set the cursor mode to Select elements.
Select the elements to be split. Elements that are not Quad 4 or Quad 8 will be ignored by this operation.
Give the Split quad elements command.
Specify how the elements are to be split in the Split quad elements dialog box.

# Refining quad and tri elements

2D elements meeting at a node (or a selection of nodes) can be split to result in a mesh refinement at the node(s). The procedure is as follows.

Set the cursor mode to Select nodes.
Select the node at which attached 2D elements are to be refined. Non-2D elements will be ignored by this operation.
Give the Refine mesh at nodes command.

Understandably, refining the mesh at more than one node on an element will have bizarre consequences.

Alternatively, Quad 4 and Quad 8 elements can be split into two elements along adjacent edges using the Sculpt > 2D element operations > Refine quad elements menu command. This may be used to bring about a mesh refinement at a corner of the existing element. The procedure is as follows.
Set the cursor mode to Select elements.
Select the elements to be refined. Elements that are not Quad 4 or Quad 8 will be ignored by this operation.
Give the Refine quad elements command.
Specify corner at which the elements are to be refined in the Refine quad elements dialog box.

# Split quad to tri elements

Quad 4 and Quad 8 element can be split into Triangle 3 and Triangle 6 elements respectively using the Sculpt > 2D element operations > Split quad to tri Elements menu command. Each quad element is split into two tri elements such that the split occurs at across the corner with largest internal angle. The procedure is as follows.

Set the cursor mode to Select elements.
Select the elements to be split. Elements that are not Quad 4 or Quad 8 will be ignored by this operation.
Give the Split quad to tri elements command.

# Splitting tri elements

Triangle 3 and Triangle 6 elements can be split using the Sculpt > 2D element operations > Split tri elements menu command. The elements can be split into either triangle or quad elements. When splitting into Triangle elements the split must be into an equal number of elements along each edge. The split options available when splitting into quad elements are described in the documentation for the Split tri elements dialog box. The procedure is as follows.

Set the cursor mode to Select elements.
Select the elements to be split. Elements that are not Triangle 3 or Triangle 6 will be ignored by this operation.
Give the Split tri elements command.
Specify how the elements are to be split in the Split tri elements dialog box.