Portal Frames
Rigid-jointed single-storey frames — the most common system for warehouses, factories and PEB buildings.
Technical Overview
A portal frame consists of columns and rafters connected by moment-resisting knee and apex joints. Lateral stability in the plane of the frame comes from the frame action; longitudinal stability usually comes from roof and wall bracing.
Applications
- Warehouses and logistics buildings
- Factories and workshops
- Agricultural buildings
- Pre-engineered buildings
Engineering Considerations
- Haunch length and depth at knees and apex
- Rafter and column restraint by purlins, girts and fly braces
- Second-order effects for slender frames
- Base fixity assumptions versus foundation design
Fabrication Considerations
- Tapered built-up members require accurate web-to-flange welding
- Repetitive frames suit automated fabrication lines
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