The OptiStruct input file is composed of three distinct sections:
- The I/O Options Section
- The Subcase Information Section
- The Bulk Data Section
The I/O Options section controls the overall running of the analysis or optimization. It controls the type, format, and frequency of the output, the type of run (analysis, check, or restart), and the location and names of input, output, and scratch files.
The Subcase Information section contains information for specific subcases. It identifies which loads and boundary conditions are to be used in a subcase. It can control output type and frequency, and may contain objective and constraint information for optimization problems.
The Bulk Data section contains all finite element data for the finite element model, such as grids, elements, properties, materials, loads and boundary conditions, and coordinates systems. For optimization, it contains the design variables, responses, and constraint definitions. The bulk data section begins with the BEGIN BULK statement.
These sections can be arranged in a one-file, two-file, or multi-file setup.
In a one-file setup, all three data sections are included in one file. The bulk data section must be the last section. It is recommended that the extension .fem be used for this file.
This setup is obsolete; the one-file or multiple-file setups are recommended.
The two-file setup separates the control data (I/O Options section and Subcase Information section) from the model data (Bulk Data section). If the input file does not contain a BEGIN BULK statement, OptiStruct will then attempt to read the model data from another file:
- If the INFILE card is present in the I/O Options section, the argument given on this card is the name of the file that contains the model data.
- If the INFILE card is not present in the I/O Options section, and the input file does not have the extension .fem, the name of the file containing the model data will be constructed from the input file by replacing the extension with .fem.
The two-file setup allows the user to perform runs using multiple control data files and a single model file and vice versa. It is recommended that the .parm extension be used for control data files and the .fem extension be used for model data files.
A multi-file setup is facilitated through the use of INCLUDE statements. This option enables the user to include information from other files without cutting and pasting. INCLUDE statements may be placed in any section of the one or two-file setup, but must include information appropriate to the section.
The following example shows how an additional subcase can be added to the Subcase Information section.
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input.fem file |
sub2.inc |
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$ Subcase 1 SPC = 1 Load = 2 $ INCLUDE sub2.inc $ BEGIN BULK $ |
Subcase 2 SPC = 1 Load = 3
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OptiStruct reads all files and positions the lines of the included file at the location of the INCLUDE statement in the input.fem file. An echo of the input.fem file as read by OptiStruct would be:
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$ Subcase 1 SPC = 1 Load = 2 $ Subcase 2 SPC = 1 Load = 3 $ BEGIN BULK $
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Notes: |
The format of the input sections in OptiStruct are similar to those of the Nastran format. |
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Names specified on INFILE and INCLUDE cards can be arbitrary file names with optional paths appropriate to the operating system (Windows or UNIX). They may be enclosed in quotes (double or single quotes can be used), and either forward slash (/) or back slash (\) characters can be used to separate parts of the pathname. OptiStruct uses the following rules to locate a file name on the INFILE or INCLUDE cards: - When the argument contains the absolute path of the file (if it starts with "/" on UNIX or a drive letter, such as "D:", on Windows, for example), OptiStruct uses the file at the given location. - When only the file name is given (without the path), the file has to be located in the same directory as the file containing the INCLUDE or INFILE statement. - When the argument contains a relative path (../filename or sub/filename, for example), it is located in the directory relative to the file containing the INCLUDE or INFILE statement and is NOT relative to the directory in which OptiStruct was executed, or to the directory where the main file is located. |
Go To
Guidelines for Bulk Data Entries
Guidelines for I/O Options and Subcase Information Entries