What Is MBS Software in Pre-Engineered Building Design?

Metal Building Software, often shortened to MBS, is a specialized analysis and design environment used by pre-engineered building teams. It is organized around PEB framing patterns rather than around a general finite-element workspace: clear-span and modular rigid frames, endwall posts, crane brackets, and roof and wall secondary systems. Engineers use it to size primary frames, check drift and deflection limits, and produce support reactions that later appear on foundation sketches and approval drawings. Knowing what the software is for—and what it is not—stops teams from treating every printed report as a finished construction document.

In a typical PEB office, MBS sits between the architectural plan and the drawing set. Someone enters geometry, loads, and member criteria. The program returns member sizes, deflections, and support forces. Those results then feed connection checks, anchor-bolt layouts, and the notes that appear on PEB approval drawings. General-purpose analysis tools can model the same frames, but MBS is built around repeating bay geometry, gable and single-slope roofs, and the secondary-member systems that make metal buildings economical. That focus is why PEB firms keep it in the workflow even when they also run STAAD.Pro or similar packages.

This guide explains MBS in engineering terms: where it belongs in a PEB project, which outputs matter, and how those outputs should be reviewed before anyone copies numbers onto a drawing. It does not replace your software version documentation, and it does not invent file-format details that change between releases. For reaction tables, see How to Read and Use MBS Column Reactions and the StruTools MBS Reactions tool. For turning checked results into a drawing package, see the StruTools MBS Approval Package.

What Metal Building Software is built to do

MBS is a PEB-oriented design environment. It expects repeating frames, standard roof shapes, and secondary systems that follow the primary frame rather than a one-off industrial structure modeled member by member from scratch.

Most PEB buildings are assemblies of interior rigid frames, endwall frames, sidewall and endwall secondary members, bracing, and covering. MBS is organized around that kit of parts. You describe building width, length, eave height, roof slope, and bay spacing, then apply gravity, wind, and other code loads according to the version of the program and the design standard you are using. The software returns member forces, suggested or checked sizes, and support reactions.

That is different from opening a blank analysis model and drawing every column and rafter as an independent element. The PEB pattern is the point: interior frames often share a geometry, endwalls may use lighter posts, and crane or mezzanine loads are applied as defined load systems. If your building is a true one-off moment frame with irregular geometry, a general analysis package may be the better primary tool. If it is a metal building, MBS is usually the faster path to a checkable frame design.

• Primary rigid frames, including clear-span and modular (multi-span) layouts
• Endwall columns and rafters, which often differ from interior frames
• Roof and wall secondary members once the primary geometry is set
• Crane, mezzanine, or collateral load cases when those systems are defined
• Support reactions at column bases for foundation and approval use

What MBS is not

Confusion starts when teams treat MBS as a complete building-information model, a connection design program, or a CAD system. It is none of those, even when its reports look dense.

• It does not replace connection design. Clip angles, base plates, rafter splices, and flange braces still need their own checks.
• It does not replace foundation design. Column reactions are input to that work, not a footing schedule.
• It does not produce a finished approval drawing set. Geometry and notes still have to be composed in CAD.
• It does not certify that loads match the architectural drawings. That remains an engineering review.
• It does not lock a member size against later architectural changes. A revised eave height is a new run, not a redline on last week's print.

Typical outputs PEB engineers actually use

Exact report names vary by software version, so follow the documentation that shipped with your license. Conceptually, PEB teams keep returning to four families of output.

Geometry and framing layout

Building width, bay spacing, eave height, roof slope, and frame type. This is the source for checking that the analysis model still matches the architectural plan and the CAD grid.

Member reports

Forces, moments, and design ratios for columns, rafters, and sometimes secondary members. Used to confirm sizes before anyone details a splice or a haunch.

Load and combination summaries

Which gravity, wind, crane, and collateral cases were applied, and how they were combined. If this list is wrong, every reaction downstream is suspect.

Support reactions

Column-base forces and moments by load case or envelope. This is the data How to Organize MBS Reaction Data into a Usable Table and StruTools MBS Reactions are built around.

How MBS fits next to STAAD.Pro and CAD

Many PEB offices run more than one analysis tool. MBS is usually the metal-building specialist. STAAD.Pro or a similar package may handle non-standard frames, mezzanines, or adjacent conventional steel. CAD remains the drawing environment.

A healthy split looks like this: MBS sizes and checks the repeating PEB frames and writes support reactions. Unusual structures—process platforms, stick-built stair towers, or a rigid frame that no longer fits the PEB template—go to a general model. CAD then receives geometry and notes, not a dump of every analysis screenshot. If you also move STAAD geometry into CAD, StruTools Staad2CAD covers that handoff; MBS still needs its own reaction and geometry review before those numbers appear on PEB sheets.

Do not maintain two conflicting models of the same frame without a written rule for which one governs. When both tools exist, label the calculation set so reviewers can see whether a given frame was designed in MBS, in STAAD.Pro, or checked in both.

Who should open an MBS model on a PEB job

Access is a quality issue. If every drafter can change eave height and every intern can re-run wind, the reaction table on the approval drawing will not match last week's foundation sketch.

• A named engineer owns load criteria, design settings, and the decision that a run is ready for drawings.
• Detailers and CAD staff receive issued geometry and reaction summaries, not unlocked model files, unless the office standard says otherwise.
• Foundation engineers receive a reviewed reaction table, not a raw print mixed with trial runs.
• Project archives keep the model, the output used for issue, and a short note on software version.

When a building is a poor fit for MBS

Forcing an irregular structure into a PEB template creates tidy reports that do not represent the real load path. Pause before you model the job as a standard metal building.

• Highly irregular plan geometry, missing bays, or frames that do not share a common ridge
• Heavy process loads that dominate the frame and are not available as defined load systems in your version
• Moment frames or braced bays that are conventional steel rather than PEB primary frames
• Existing buildings where you only need a local check, not a full metal-building redesign

A first-week MBS workflow on a PEB job

New team members do not need every report on day one. They need a repeatable path from building criteria to a checked output set.

1. Collect architectural dimensions, design code, site wind and snow criteria, crane data, and special owner loads.
2. Build the MBS model from those criteria and record the software version in the calculation header.
3. Run the analysis and scan geometry, load combinations, and support conditions before reading member sizes.
4. Review member reports for the governing frames, then extract column reactions for foundation and approval use.
5. Store the model, the output used for issue, and a reaction table together so later revisions have a baseline.
6. Only then start CAD work for frame elevations, anchor-bolt plans, and reaction notes.

Engineering tips

• Write the software version and design standard on the calculation cover before you print member reports.
• Treat interior frames and endwall frames as different families even when the building looks rectangular.
• If architectural drawings change eave height or crane capacity, re-run MBS; do not scale last week's reactions.
• Keep trial runs out of the folder that foundation and CAD staff are told to use.
• Link the issued reaction table to the drawing issue number so reviewers can see which analysis supports which sheet.

Common mistakes

Using MBS as if it were CAD

The model is a calculation. Screen graphics help you check geometry, but the issued building is defined by drawings, not by an analysis screenshot pasted on a sheet.

Copying reactions from an unfinished run

Partial load combinations, missing crane cases, or supports that were never applied will still print numbers. Those numbers can look complete. MBS Output Quality Checks Before Using Results in Design Workflows exists because this mistake is common.

Ignoring endwall differences

Endwall posts often carry different loads and may not match interior frame reactions. Mixing them in one unlabeled column of a table sends the wrong force to a footing.

MBS project setup checklist

Use this before the first issued run, not after CAD has already dimensioned the frames.

• Building width, length, eave height, and roof slope match the architectural issue in hand.
• Bay spacing and frame types (clear-span vs modular) are written down, not assumed from a previous job.
• Wind, snow, seismic, crane, and collateral criteria are listed with the code edition.
• Software version is recorded on the calculation header.
• A named engineer owns the model settings.
• Output folders separate trial runs from the issued set.
• Reaction extraction method is agreed (manual table, spreadsheet, or StruTools MBS Reactions).
• CAD and foundation recipients are named so the table is not emailed into a void.

Frequently asked questions

Is MBS the same thing as a general structural analysis program?

No. MBS is built around pre-engineered metal building framing. General programs can model the same geometry, but they are not organized around repeating PEB bays, endwalls, and secondary systems. Many offices use both.

Can MBS output go straight onto approval drawings?

Not without review. Geometry and reactions are source data. Someone still has to check units, load cases, and orientation, then compose sheets in CAD. See From MBS Output Files to PEB Approval Drawings.

Do I need MBS if the building is already in STAAD.Pro?

Only if your office standard says PEB frames are designed in MBS. Duplicate models of the same frame need a written rule for which results govern. Do not silently mix reactions from both.

Where should column reactions be stored?

In a reviewed table tied to the model version and drawing issue, not only inside a printout. StruTools MBS Reactions is one way to organize that table.

Treat MBS as a PEB design tool, not a drawing factory

MBS earns its place because PEB frames repeat. Used that way, it produces member sizes and support reactions that a competent team can review and issue. Used as a black box, it produces tidy numbers that nobody can defend when a footing is poured to the wrong load case.

Next, read Understanding MBS Output Files for PEB Engineering so you know which reports to keep, then How to Read and Use MBS Column Reactions before those forces reach a foundation sketch or an approval note.