NASTRAN File: Bulk Data Entries

Description

This section contains most of the data in a NASTRAN file. Node coordinates, element connections, attributes, properties and materials all appear here. Bulk data begins with BEGIN BULK and ends with ENDDATA. Straus7 imports and exports most of the common bulk data entries.

Each entry is formatted using the following rules:

Each entry is composed of fields. There are three formats: small (8 characters per field), large (16 characters per field), or free (unlimited number per field, fields separated by commas).
There are 10 fields per line for small and free format; six fields per line for large format. For small and large format, the first and last fields on each line are always 8 characters.
The first field for each entry is the NASTRAN identifier, a string of up to 7 characters. For example, the node identifier is GRID. The identifier must start at the first position in the first field.
Small format is the default format; an asterisk (*) immediately after the identifier indicates the data is in large format; a comma (,) anywhere in the first 10 characters indicates free format.
If more than one line is required to fully specify an entry, the last field in each line contains a continuation identifier, which is used in conjunction with the first field in the next line. Continuation identifiers must be unique.
The first character in a continuation indicates the format for that continuation. If the first character is blank, a comma (,) or a plus (+), the continuation is in small format. An asterisk indicates large format. If the format is initially free format, this must be maintained throughout the entry.

Straus7 only imports data where all continuations have the same format as the first line in the entry.

The data that would fit on a single line in small format must be written as two lines in large format. This means entries in large format must always have an even number of lines, even if the second line contains no useful data.