Creating Custom Cross Sections with a User-Defined Mesh
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13.3.2. Creating Custom Cross Sections with a
User-Defined Mesh
If you need to define a cross section that is not common, you must create a user mesh file. To create a user mesh file, create a 2-D solid model and save it using the SECWRITE command (Main Menu> Preprocessor> Sections> Beam> Custom Sectns> Write From Areas). This procedure is outlined in greater detail below:
1.Create all areas (Main Menu> Preprocessor> Modeling> Create>
Areas).
2.Overlap the areas (Main Menu> Preprocessor> Modeling>
Operate> Booleans> Overlap> Areas) or glue them (Main Menu> Preprocessor> Modeling> Operate> Booleans> Glue> Areas)
where appropriate.
3.Save the model.
4.Set the number of line divisions for all lines (Main Menu>
Preprocessor> Meshing> Size Cntrls>ManualSize> Lines>
Picked Lines or use the MeshTool).
5.Select Main Menu> Preprocessor> Sections> Beam> Custom
Sectns> Write From Areas. A picker appears. Pick the area(s) of the
cells.
6.The program creates cells on the areas. Bad shape messages may
appear during the mesh, but you can ignore them. You may, however,
see an "Unable to mesh area ...." message; if you do, clear the elements
from all areas (Main Menu> Preprocessor> Meshing> Clear>
Areas) and repeat steps 4 and 5.
7.Write the .SECT file out to a unique name in the Write Section Library
File dialog and click OK.
8.Read in the user mesh file (Main Menu> Preprocessor> Sections>
Beam> Custom Sectns> Read Sect Mesh) to calculate the section
properties. Material properties must be defined to calculate the cross
section shear correction factors, material-weighted centroids and the
shear centers.
13.3.2.1. Line Element Size
Even if you have already set the line element size (LESIZE), you will see the following message:
Line element sizes may need to be specified for desired cross-section mesh. Please refer to the LESIZE command.
If you have already set the line element size, click the Close button to continue. If you have not already set it, issue LESIZE with the appropriate information. When creating cells on the area using the GUI, it is not necessary to define a plane element type. On the other hand, you must define a plane element type and mesh the area if you issue the SECWRITE command
explicitly. MESH200 with KEYOPT(1) = 7 and PLANE183 are the only valid plane element types.