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.

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, which may have bizarre consequences. 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.

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.

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

1. Set the cursor mode to Select nodes.
2. Select the node at which attached 2D elements are to be refined. Non-2D elements will be ignored by this operation.
3. 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.

1. Set the cursor mode to Select elements.
2. Select the elements to be refined. Elements that are not Quad 4 or Quad 8 will be ignored by this operation.
3. Give the Refine quad elements command.
4. 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.

1. Set the cursor mode to Select elements.
2. Select the elements to be split. Elements that are not Quad 4 or Quad 8 will be ignored by this operation.
3. 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.

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