How to Export PEB Tapered Members from STAAD to IFC Correctly

Exporting Pre-Engineered Building (PEB) models from STAAD to BIM applications like Revit or Archicad often looks simple on paper—but users quickly realize a common problem: tapered members (rafters, columns) don’t translate correctly into IFC.

This leads to distorted geometry, missing section data, or generic “dumb” solids in Revit/Archicad.

At CTtec, we’ve tested and refined a workflow that ensures tapered PEB members appear correctly in BIM software without losing structural accuracy.

Why Tapered Members Cause Issues in IFC

Pre-Engineered Buildings (PEBs) rely heavily on tapered steel members. Rafters, beams, and columns are often designed with variable depths to optimize material use and span large distances cost-effectively.

The challenge is that STAAD defines tapered members with START and END section properties, but IFC expects prismatic or parametric definitions. As a result:

• IFC export treats tapered beams as “uniform” members.
• Revit and Archicad often display them as incorrect or generic solids.
• Schedules and quantities can become unreliable.

That’s why engineers must carefully prepare models before IFC export.

Step-by-Step: Export PEB Tapered Members from STAAD to IFC

Here’s the proven workflow we recommend:

In STAAD – Prepare the Model

🔹 Identify tapered members

• Typically rafter beams or columns in PEB frames.
• In STAAD, they’re defined with START and END section properties.

🔹 Switch to Physical Model workflow

• Go to Workflow → Physical Model.
• Physical members are IFC-friendly and preserve intent better.

🔹 Break tapered members into segments

• Instead of one beam with varying depth, split it into 3–5 prismatic segments.
• Each segment should have a constant section property.
• Match start/end sizes to recreate your taper.

Benefit: This gives BIM tools something they can actually understand.

Export STAAD Model to ISM

• In STAAD: File → ISM → Create Repository
• Save as .ism.dgn file.
• STAAD will launch iTwin Analytical Synchronizer automatically.

When you export PEB tapered members from STAAD to IFC, the best practice is to split them into prismatic segments before mapping in iTwin.

In iTwin Analytical Synchronizer – Map Profiles

• Review Section Mapping dialog.
• For each PEB segment, ensure it maps to a known BIM section (e.g., I-Section 300×150).

If your exact size doesn’t exist:

• Create a custom section in iTwin.
• Name it consistently (so Revit/Archicad can recognize).

Export to IFC

• In iTwin: File → Export → IFC
• Choose IFC 4 (preferred – better tapered geometry support).
• Save .ifc.

Import into Target BIM Application

For Revit:

• Use Link IFC (not Import).
• This allows easy reloading when STAAD changes.
• If you need parametric tapered beams, swap the linked geometry with a custom Revit Family.

For Archicad:

• Use File → Open/Merge → IFC.
• In translator settings, ensure beams map as Archicad Beams (not generic objects).

Optional – Keep a Reference Solid

For visual QA/QC, also export a 3D solid:

• From STAAD: Export → DWG/DXF (3D)
• Or export to MicroStation DGN → SAT/DWG
• Link this into Revit/Archicad for exact visual comparison.

The Result

• Each PEB frame appears correctly sized in BIM software.
• Tapered members are preserved (via segmented approach).
• Data is ready for schedules, reports, and clash checks.

Why This Matters

Across UK, UAE, India, and the Middle East, PEB structures are widely used in industrial warehouses, logistics hubs, and factories. These projects require seamless structural-to-BIM workflows because:

• Architects in Revit/Archicad need accurate geometry.
• Contractors need correct tapered sections for clash detection.
• Steel fabricators depend on reliable data for fabrication.

When you export PEB tapered members from STAAD to IFC correctly, you ensure:
✔ Accurate geometry transfer.
✔ Reduced rework and time loss.
✔ Confidence in BIM coordination.

Pro Tips for Smooth Export

• Always test your IFC in a free viewer (like Solibri or BIMcollab Zoom) before sharing with architects.
• Stick to consistent units (meters vs millimeters).
• Keep a section mapping log for repeat projects.
• If you’re working on mega-projects in the Middle East, validate tapered members early to avoid late-stage redesign.

 CTtec Expertise

At CTtec, we help engineers across the UK, UAE, and India get the most from Bentley STAAD workflows.

Contact us: support@CTtec.org | Visit: www.CTtec.org | CTtec London, UK | Dubai, UAE | India

References

1. Bentley Systems – STAAD.Pro Product Page https://www.bentley.com/software/staad/
2. Bentley iTwin Analytical Synchronizer – Official Documentation https://www.bentley.com/software/itwin-analytical-synchronizer/
3. buildingSMART International – IFC Standards
   https://www.buildingsmart.org/standards/ifc/
4. Autodesk – Revit IFC Support & Guidelines
   https://help.autodesk.com/view/RVT/IFC/
5. Graphisoft – Archicad IFC Interoperability Guide
   https://graphisoft.com/solutions/archicad/open-bim/ifc
6. CTtec – Engineering Software Solutions
   https://www.cttec.org