Engineering Tools

Bulk Deck to Free Format

Engineering Tools — Bulk Deck to Free Format (00229)

What this tool does

Converts a Nastran short-format bulk-data deck (8-character fixed-width fields) to free format (comma-separated fields). Reads any .bdf, .nas, or .dat file the user picks, writes a sibling *_FREE.bdf next to it.

Free format is easier on the eyes when reading bulk decks in a text editor — commas separate fields, no need to count to column 16 to find field 2. Some preprocessors also produce cleaner diffs against free-format decks.

v1.03 — QRG-compliant continuation handling

The 1.03 revision rewrites the continuation logic to match the Nastran Quick Reference Guide's free-format rules exactly:

  • A trailing comma at end-of-line continues the card on the next line.
  • Continuation lines do NOT need a leading + or star-prefixed continuation ID.
  • Field count per line is unrestricted in free format (the preprocessor accepts as many comma-separated fields as fit).

Pre-1.03 versions emitted Nastran-style continuation IDs in the free-format output, which some downstream preprocessors choked on. v1.03 emits true free format and is QRG-compliant.

v1.03 — tolerates bare card extracts

If the input file is a fragment that lacks the BEGIN BULK sentinel (common when someone pastes a card sequence into a sidecar file for inspection or sharing), v1.03 still converts the cards correctly. Earlier versions required the sentinel and bailed otherwise.

How to use it

  1. Open from Custom Tools > File Processing > Bulk Deck to Free Format.
  2. Pick the input .bdf / .nas / .dat file via the file picker.
  3. Click OK. Output is written to a sibling <original-name>_FREE.bdf file. The original is left untouched.

Worked example

  Input (short format):
  GRID    1               0.0     0.0     0.0
  GRID    2               1.0     0.0     0.0
  CBAR    100     1       1       2       0.0     0.0     1.0
  $
  PBAR    1       1       1.0     0.0833  0.0833  0.0
  $
  MAT1    1       3.0E+7          0.30

  Output (free format):
  GRID, 1, , 0.0, 0.0, 0.0
  GRID, 2, , 1.0, 0.0, 0.0
  CBAR, 100, 1, 1, 2, 0.0, 0.0, 1.0
  $
  PBAR, 1, 1, 1.0, 0.0833, 0.0833, 0.0
  $
  MAT1, 1, 3.0E+7, , 0.30

Failure modes

  • Unrecognised card. The converter respects the QRG card list but unrecognised user-bulk or solution-specific cards pass through unchanged. If a card looks malformed in the output, verify against the QRG.
  • Comments preserved. Lines starting with $ are passed through verbatim, including spacing.
  • Mixed-format input. If the input has some free-format and some short-format cards, those already in free format pass through unchanged; only short-format cards get converted.

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