From MBS Output Files to PEB Approval Drawings

Approval drawings are the first sheets many clients, contractors, and foundation engineers will trust. They are not a reprint of MBS. They are a composed set: cover, plans, frame elevations, cross-sections, anchor-bolt layouts, and design data. MBS supplies geometry, member sizes, and support reactions. CAD and checking supply the sheets. The handoff fails when someone pastes a report onto a layout and calls it an approval package, or when CAD redraws frames from memory while the model quietly used different eave heights.

The useful question is not 'how do I export a drawing from MBS?' Exact export tools change by version, and many offices still draft approval sheets in AutoCAD from issued dimensions. The useful question is which output belongs on which sheet, and what must be checked before that number or dimension is allowed to appear. That mapping is what this guide covers, as a companion to How to Read and Use MBS Column Reactions and Coordinating MBS Results with CAD and PEB Approval Drawings.

StruTools treats the drawing-side work as a package problem, which is why the StruTools MBS Approval Package exists: reduce repetitive composition once the engineering data is already reviewed. It does not replace the mapping below. If reactions are still a pile of prints, organize them first with StruTools MBS Reactions or the table method in How to Organize MBS Reaction Data into a Usable Table. Only a reviewed table should ever appear on an issued sheet.

Approval drawings consume issued data, not live models

The CAD operator should not be attached to an unlocked MBS session. Sheets should be built from a frozen extract that a named engineer has marked as supporting that issue letter.

Write the analysis issue on the drawing: software version, run date, and the folder or document number of the output package. When the building changes, the next drawing issue cites the next analysis issue. That trail is more important than any one dimension.

Numbering and revision letters should follow the office system, including approval drawing numbering if that is your standard. Do not invent a parallel numbering scheme for 'MBS sheets' that nobody can file.

Map geometry before you map reactions

If the elevation is the wrong width, the reaction table on the same sheet is already untrustworthy. Geometry is the first copy operation.

• Bay spacing and building width from the geometry summary become the CAD grid.
• Eave height and roof slope become the frame elevation.
• Interior versus endwall frames become separate elevations or clearly labeled typical views.
• Support locations become grid bubbles on the anchor-bolt plan.
• Openings and crane locations become notes that they were included in the analysis—or that they were not.

Member sizes on elevations

Clients read member sizes off frame elevations. Those sizes have to come from the governing member report, not from a previous job that 'looked similar'.

Typical interior frames can be shown as a typical elevation with a schedule of sizes. Non-typical frames—crane bays, stepped eaves, frames beside large openings—get their own views. If MBS designed secondaries, do not silently copy those sizes onto a primary-frame elevation.

When a size changes after a client comment, re-run or re-check the model. Changing a rafter on the drawing without changing the analysis is how reactions and sizes drift apart.

Reactions on the approval set

A reaction table on an approval drawing is a public statement. It should be shorter than the calculation extract and stricter about labels.

• Show grid marks that match the plan.
• Show units and whether values are service or factored.
• Show the load cases the table contains, or point to the calculation extract for the full set.
• Show uplift separately from compression.
• Cite the analysis issue letter so a later revision cannot reuse last week's numbers quietly.

What should never be copied onto an approval sheet

Some MBS output is useful in the calculation book and harmful on a client-facing drawing.

• Unfiltered combination dumps with no governing-case labels
• Trial geometry that was never marked issued
• Solver warnings, except as a reason the package is not ready
• Internal member IDs that do not map to grid marks
• Screenshots of the post-processor in place of dimensioned views

Build the package, not a stack of plots

An approval issue is a set: cover sheet, index, drawings, and a transmittal that names the analysis source. Automation helps after that structure exists.

The StruTools MBS Approval Package is aimed at the repetitive composition of that set once engineering data is ready. It will not invent missing reactions or guess a bay spacing you never issued. Complete the MBS review first, including MBS Output Quality Checks Before Using Results in Design Workflows.

CAD standards—layers, blocks, title attributes—still apply. See AutoCAD Layer Standards for Structural Steel Drawings when the PEB set lives in AutoCAD.

From issued MBS run to approval issue

Keep analysis freeze and drawing freeze in a single sequence.

1. Freeze the MBS run and file the output package with a cover (version, reviewer, date).
2. Extract geometry and a reviewed reaction table from that package only.
3. Build or update CAD grids and frame elevations from the geometry extract.
4. Place member sizes from the governing member summary.
5. Place the reaction table or a pointer to it on the anchor-bolt or design-data sheet.
6. Index the set, apply the issue letter, and cite the analysis issue on the transmittal.
7. Archive the drawing issue next to the analysis package so the pair can be retrieved together.

Engineering tips

• Put the analysis issue letter in the drawing title block or a dedicated note, not only in an email.
• If one frame changed, say so on the transmittal; do not reissue twenty sheets with no indication of what moved.
• Keep endwall elevations out of the typical interior-frame sheet unless they truly match.
• When the client changes crane capacity, treat it as a new analysis issue, then a new drawing issue.
• Do not let CAD 'clean up' a grid that no longer matches the model without sending the change back to analysis.

Common mistakes

Pasting the member report as a drawing

A calculation print is not dimensioned, not numbered, and not checkable as a sheet. Compose the elevation.

Updating CAD without a new analysis issue

A redline that changes eave height is an analysis change. If you only edit CAD, reactions on the same sheet become fiction.

Leaving reactions in a spreadsheet nobody cites

If the drawing does not point to the table, field and foundation users will invent their own. Cite it.

MBS-to-approval issue checklist

All items are about matching, not about how pretty the title block is.

• Issued MBS package exists with reviewer name and software version.
• CAD grid matches geometry summary.
• Frame elevations match eave height and slope from that summary.
• Member sizes match the governing member report.
• Reaction table matches the reviewed extract and cites units.
• Interior and endwall frames are not silently mixed.
• Drawing issue letter and analysis issue letter are both visible.
• Transmittal lists what changed if this is not issue A.
• Calculation package is archived with the drawing issue.

Frequently asked questions

Can MBS print approval drawings for me?

Some versions offer drawing or report exports. Treat those as drafts or calculation figures unless your office standard says otherwise. Most PEB approval sets are still composed in CAD from issued data.

Which sheet should carry the reaction table?

Usually the anchor-bolt plan or a design-data sheet that uses the same grid as the plan. Follow your office standard and keep units on the table.

What if the client approves the drawings and then the model changes?

That is a new analysis issue and a new drawing issue, with a transmittal that says what changed. Do not quietly edit the approved set.

How does this relate to shop drawings?

Approval drawings establish geometry, reactions, and member intent. Shop and fabrication drawings add connection and piece-level detail. Do not skip approval and jump to shop from a raw MBS print.

The drawing is the public copy of the calculation

MBS output becomes an approval package only after geometry, sizes, and reactions are mapped onto numbered sheets that cite the analysis issue. Until then you have calculations and you have CAD, but you do not have a package.

For the CAD mechanics of that mapping, continue with Coordinating MBS Results with CAD and PEB Approval Drawings. For the reaction table those sheets depend on, stay with How to Read and Use MBS Column Reactions.