MBS
How Engineering Teams Can Organize MBS Files and Project Outputs
MBS models, trial runs, issued output, and reaction tables need a folder and naming scheme so PEB teams can find the current analysis without opening every file.
Lost MBS files create the same errors as bad analysis, just more slowly. Someone opens last week's model, reprints reactions, and CAD never hears that eave height changed. Someone else archives nothing but a PDF in email. Organizing MBS files is not clerical busywork. It is how a PEB team keeps the issued run, the signed table, and the drawing issue pointing at the same building. If the folders are wrong, PEB Reaction Data Workflow: From Software Output to Engineering Review has nothing reliable to move.
This guide proposes a simple tree: models, trial output, issued output, reaction tables, and a cover note. It does not require a particular document-management product. It does require that trial and issued files never share a directory, and that names contain the project and the analysis issue letter. Pair it with CAD File Management Practices for Structural Engineering Projects so drawing folders and analysis folders use the same issue language.
Exact MBS model extensions and autosave names depend on your software version; follow that documentation. Do not build an office standard around unofficial file-format trivia. Build it around roles: which file may be edited, which file may be extracted from, and which file is frozen. Extraction tools such as StruTools MBS Reactions should be aimed only at the issued folder. Understanding MBS Output Files for PEB Engineering lists what that folder should contain.
Separate editable models from issued snapshots
The working model changes. The issued snapshot does not. If they are the same file, you cannot reconstruct what foundations used.
- Keep a working model directory for the analyst.
- When a run is issued, copy or export a snapshot into the issued package for that letter.
- Do not let CAD staff pull from the working directory.
- Record software version next to the snapshot, not only next to the working file.
A folder tree that survives a busy week
Deep trees nobody follows are worse than a shallow tree people actually use.
Example, to be adapted to your server: Project / 03-Analysis / MBS / Working, Project / 03-Analysis / MBS / Trial, Project / 03-Analysis / MBS / Issued-A, Project / 03-Analysis / MBS / Issued-B, Project / 03-Analysis / Reactions. CAD lives elsewhere but uses the same issue letters. The names matter more than the numbers on the folders.
What belongs in each MBS folder
| Folder | Contains | Who writes |
|---|---|---|
| Working | Current model(s) being edited | Frame analyst |
| Trial | Output from incomplete or rejected runs | Analyst, then ignore |
| Issued-letter | Frozen model snapshot, reports, diagnostics, checklist | Analyst + reviewer |
| Reactions | Signed tables named with the same letter | Reviewer after sign-off |
Name files so a stranger can sort them
File names are a user interface. 'final2' is not a user interface.
- Project code, building or frame line if needed, document type, analysis issue, date.
- Example pattern: P123-BldgA-MBS-react-B-2025-11-14.
- Do not encode 'latest' in the name. The issued folder is what makes it latest.
- Keep the same project code CAD uses on approval drawing numbering.
Covers, checklists, and reaction tables live with the issue
An issued folder without a cover is a pile. Put the one-page cover, the quality checklist, and a pointer to the signed table in that folder.
The quality checklist from MBS Output Quality Checks Before Using Results in Design Workflows is part of the issued package, not a personal notes file. The signed reaction table can live in the Reactions folder if the cover points to it with the same letter. Do not store the only copy of the table on a desktop.
Access and backups are quality controls
If anyone can overwrite Issued-B, you do not have an issued package.
- Working is writable by the analyst role.
- Issued folders are read-only after sign-off, or writable only by a document controller.
- Trial can be purged on a stated schedule after the corresponding issue exists.
- Backups must include issued folders; a backup of Working alone is not a project record.
Coordinate with CAD without merging the trees
Analysis and CAD can share issue letters without sharing directories. Merging them usually leads to DWG files sitting next to solver scratch files.
CAD file practice is covered in CAD File Management Practices for Structural Engineering Projects. The link between trees is the issue letter and a transmittal, plus Coordinating MBS Results with CAD and PEB Approval Drawings for the actual geometry mapping.
Opening a new PEB analysis directory
Do this on day one, before the first MBS run, while the job still looks simple.
- Create Working, Trial, Issued, and Reactions folders using the project code.
- Agree the analysis issue letters with CAD so drawing issues can cite them.
- Place a blank cover template in Issued.
- State who may write to Working and who may freeze Issued.
- Run the first model in Working; dump failed output only to Trial.
- When the gate passes, copy the snapshot and reports into Issued-letter and lock it.
Engineering tips
- Put the issue letter in the folder name, not only inside a Word cover that nobody opens.
- Keep a one-line current-issue pointer at the project root, updated when letters change.
- Do not store reaction Excel files in Working. They will be overwritten.
- If two buildings share a site, split folders by building before the first run.
- Purge Trial on a schedule so it cannot be mistaken for Issued.
Common mistakes
One shared 'MBS' folder for the whole office
Project codes exist so jobs do not overwrite each other. A communal directory will mix models.
Email as the archive
Attachments in a thread are not a folder tree. They also strip names and duplicate copies.
Editing files inside Issued because it was convenient
That is a new issue. Copy to Working, change, re-issue as the next letter.
MBS filing checklist
If this fails, the analysis record is not reviewable.
- Working and Issued are different directories.
- Trial is not mixed with Issued.
- File names contain project code and issue letter.
- Issued folder contains snapshot, reports, diagnostics, and checklist.
- Signed reaction table is findable from the issued cover.
- Issued folder is protected from casual overwrite.
- CAD uses the same issue letters.
- A current-issue pointer exists at project level.
Frequently asked questions
Should we zip issued packages?
A packed archive is a good freeze format if your server cannot lock folders. Keep the zip name identical in meaning to the folder name.
How long should trial output be kept?
Until the corresponding issue is signed is the minimum. After that, a short retention is enough. Do not keep trial files in a place CAD can see.
Do model autosaves belong in Issued?
No. Autosaves belong in Working or in a cache you ignore. Issued contains only what the reviewer signed.
Where should [StruTools MBS Reactions](/tools/mbs-reactions) write its table?
Into the Reactions folder, named with the analysis issue, never into Working.
If you cannot find the issued run, you do not have one
Folder trees will not design a frame. They will prevent last week's trial from becoming next week's foundation input. Separate working, trial, and issued; name files with the same letters CAD prints; lock what you have signed.
Once files stay put, the technical mapping to drawings is Coordinating MBS Results with CAD and PEB Approval Drawings, and the overall sequence remains PEB Reaction Data Workflow: From Software Output to Engineering Review.
This article provides general educational information. Project-specific structural design, calculations and drawings should be reviewed by appropriately qualified engineering professionals and checked against applicable project requirements and standards. StruTools does not replace engineering judgement or professional design review.