PEB Design Workflow: From Structural Analysis to Fabrication Drawings

A PEB project does not fail because someone forgot the name of a purlin. It fails when analysis, approval drawings and shop data describe three different buildings. The workflow that prevents that is unglamorous: freeze geometry, analyse the frames that actually match that geometry, publish reactions from the same model, and only then detail pieces. Skipping a freeze feels faster until the ridge moves and every tapered web is wrong.

Teams that live in metal-building software, STAAD.Pro and CAD at the same time feel this drift first. An MBS run may size frames, a STAAD model may be used for a consultant check, and AutoCAD or Tekla may hold the drawing. Each environment can be correct in isolation and still disagree on eave height. This guide is a practical sequence from structural analysis to fabrication drawings, written so engineers and detailers can see where their work should wait for someone else.

If you are still defining the system itself, start with what a pre-engineered building is. If your immediate problem is the sheet set, jump to the PEB approval drawing process. Here the subject is the path between those worlds, including where StruTools MBS Reactions or Staad2CAD can reduce retyping — without treating software as the design.

Inputs worth freezing before anyone opens the analysis file

PEB software will happily analyse an incomplete building. The cost appears later, when openings, cranes and roof equipment show up as “small extras.” Collect the architectural envelope, the named design basis, geotechnical notes that affect base fixity assumptions, and a written list of special loads. If a value is unknown, record the assumption on the cover notes so it can be replaced later without folklore.

• Plan dimensions, bay spacing, expansion joints and future-extension bays.
• Eave height, roof slopes, ridges, valleys, canopies and soffits.
• Wall materials that change girt restraint or wind on the structure, including masonry and architectural panels.
• Crane class, spans, runway elevations and any maintenance walkways.
• Mezzanine locations, floor construction and whether the PEB columns support them.
• Rooftop units, solar, sprinklers and hanging conveyors with enough information to place the load, not just a kPa guess in an email.
• Openings larger than a personnel door, including docks and ventilation.
• Corrosion and fire-protection decisions that change member type or exposed steel.

Analysis that matches the building you intend to draw

Frame analysis is not a separate art project. The model must use the same width, slope, haunch philosophy and support conditions that the drawings will show. Many PEB offices size primary frames in metal-building software, then export or rebuild critical frames in a general tool when a consultant asks for an independent check. Either path is fine if the geometry is identical. It is not fine if STAAD has prismatic members while the shop is welding tapers.

Primary frames first

Model interior rigid frames, endwalls and any stepped or crane frames as the geometry will be built. Releases, base conditions and bracing representation should match the intended system, not a default pinned-base template from another country.

Secondaries as loads or as members

Some workflows apply purlin and girt loads to frames without modelling every cold-formed member. Others include secondaries when their restraint or continuity matters. Choose deliberately. If flange braces are required for rafter stability, they must exist in the design intent, not only in a typical detail.

Reactions as a deliverable, not a screenshot

Support reactions should be tabulated for the combinations named in the design basis, with axes and sign convention stated. Understanding column reactions in PEB design and reading STAAD.Pro support reactions cover the reading problem. Offices that process MBS printouts often use StruTools MBS Reactions to get those numbers into a reviewable table.

Approval drawings are a control gate, not a pretty print of the model

Once frames are sized, the temptation is to start piece marks. Resist it until approval drawings tell the consultant what building you intend to supply. Approval sheets should show overall geometry, member marks, bracing, secondary layout, anchor setting and notes. They are not shop drawings. Their job is to freeze interfaces: civil, architecture, owner equipment and the steel supplier.

A practical PEB approval set is described in the dedicated approval drawing process guide. In the workflow, treat approval as the moment analysis, reactions and geometry are allowed to be seen by others. If the consultant comments “move grid 4,” that comment must return to the analysis model, not only to CAD. StruTools MBS Approval Package is one way teams keep that set together; the important part is the discipline, not the tool.

Detailing and fabrication data after the building is agreed

Shop drawings, CNC files, bolt lists and shipping marks come after approval comments are closed or formally deferred. Detailing too early produces beautiful drawings of the wrong haunch. The detailing model should inherit member sizes, bolt grades assumed in design, and the connection families the engineer actually checked — not a favourite typical from another fabricator.

Reviews that belong in the workflow, not at the end

Quality control is cheaper as a series of gates than as a final panic. Each gate asks a different question. Geometry freeze asks whether the building is the one the owner wants. Analysis review asks whether the model matches that building. Approval review asks whether other disciplines can build around it. Shop review asks whether the piece can be fabricated and erected from the information given.

1. Geometry gate: envelope, cranes, openings and future bays signed off internally.
2. Model gate: supports, releases, member properties and load cases reviewed before design is treated as final. See the STAAD.Pro model checking checklist if that is your analysis tool.
3. Reaction gate: foundation engineer can use the table without guessing axes.
4. Approval gate: comments logged, not lost in marked PDFs on a personal drive.
5. Detailing gate: connection design intent versus shop typicals reconciled.
6. Fabrication gate: revisions that affect CNC are issued as revisions, not verbal instructions.
7. As-built or site-query gate: field changes return to engineering instead of dying in a WhatsApp group.

Software is a lane in the workflow, not the workflow

MBS, STAAD.Pro, Excel, AutoCAD, Tekla and LISP routines each occupy a lane. The workflow is the rule for when data is allowed to jump lanes. Exporting STAAD geometry toward CAD, for example, is useful after the model has survived checking — not as a way to skip checking. That conversion path is discussed in STAAD.Pro to AutoCAD and the broader structural model to CAD workflow.

A healthy PEB office writes down which program is master for geometry, which is master for member size, and which is master for drawings at each stage. When those masters are unspoken, the loudest file wins. Common software used in PEB design and detailing maps the usual stack without turning this workflow article into a vendor list.

End-to-end PEB production sequence

Use this as a project board. If a later step is underway while an earlier freeze is open, you are already in rework.

1. Issue an input register: geometry, design basis, special loads, interface owners.
2. Build or update the primary-frame analysis model to match the register, not the previous job.
3. Run analysis, review member utilization and deflections against project limits, then lock member sizes.
4. Extract and check support reactions; send a dated table to foundations.
5. Draft approval drawings from the locked geometry and sizes; circulate internally first.
6. Submit approval, log comments, and recirculate only changed sheets with a visible revision.
7. Release detailing after comments are closed or listed as deferred with engineering sign-off.
8. Issue fabrication and erection data from the detailing model; archive the analysis file that matches that issue.

Engineering tips

• Put the analysis file name and revision on the approval cover sheet so later investigators can find the matching model.
• Never let a detailer invent a crane bracket that was not in the analysis.
• If architecture issues a clouded plan, stop detailing in the clouded area even if the rest of the building is approved.
• Keep a one-page member-size list as a human-readable bridge between software environments.
• Agree PDF layering and stamp workflow with the consultant before the first submission.
• When you reuse a previous PEB model, delete its loads and supports first, then rebuild them from this project’s basis.
• Treat Excel reaction workbooks as controlled documents: date, combination list, axis sketch.

Workflow failures that look like software bugs

Detailing in parallel with a still-moving architectural plan

Parallel work only helps after interfaces are frozen. Before that, every door move creates orphan holes and wrong girt splices.

Using a STAAD check model that does not share geometry with the PEB sizing model

If the independent check has different haunch lengths, it is not a check. It is a different building that happens to have a similar span.

Issuing reactions from an envelope the drawings do not mention

Civil will design for what you sent. If approval notes describe a different combination set, the foundation and the frame no longer belong to one design.

Closing approval comments in CAD only

A clouded rafter depth that is edited on the elevation but not in the analysis file will return as a site problem when connections are already welded.

Handing the shop a model with leftover trial members

Unused frames, dummy members and old load cases surviving in the file become wrong piece marks. Purge before release.

PEB workflow health check

Run this at each release, not only at the end of the job.

• Input register exists and is dated.
• Analysis geometry matches the current architectural envelope.
• Load cases and combinations match the design basis document, not a previous project file.
• Member sizes on drawings match the analysis output used for this revision.
• Reaction table uses the same column marks as the approval plan.
• Approval comments are logged with sheet numbers and status.
• Deferred comments are listed, not forgotten.
• Detailing has not started in unapproved areas.
• Connection typicals applied by the shop were reviewed for this frame’s forces.
• Fabrication data is issued from one master detailing model.
• Superseded PDFs are marked superseded, not merely emailed again.
• Site queries have a path back into engineering documents.

Frequently asked questions

Should fabrication drawings start before PEB approval is stamped?

Only for items the contract explicitly allows at the supplier’s risk, and even then not for members affected by open comments. Starting the whole shop set early usually means paying twice when grid lines move.

Where does STAAD.Pro sit if the frames were sized in MBS?

Often as a check model, a way to study an unusual frame, or a source of geometry for CAD. It only helps if node coordinates, tapers and supports match the MBS building. See PEB engineering software for how those tools usually share the job.

What is the minimum that must go to the foundation engineer?

Column marks, base location, reaction components with sign convention, the combinations represented, and whether bases are pinned, fixed or something in between. A screenshot of a model is not enough.

How do you keep AutoCAD from becoming a second analysis model?

CAD should not invent member depths. Import or type sizes from the locked analysis list. If a drafter needs a different depth for a clash, that is an engineering change, not a drafting preference.

The workflow is the product

PEB engineering looks like software, drawings and steel. The actual product of the design office is a controlled sequence: one geometry, one analysis revision, one reaction table, one approval set, then shop data that can still point back to that revision. When those artefacts diverge, fabrication becomes a negotiation.

Use this sequence with the approval drawing process and design coordination articles. Project-specific member design, load combinations and connection checks remain the duty of the responsible engineer. StruTools tools can reduce transcription inside that sequence; they do not certify the building.