Primary Framing
Interior Columns for Multi-Span Steel Buildings
Definition: An interior column is a vertical member placed inside a multi-span rigid frame to support the rafter between the exterior columns. It shortens the rafter span, reducing bending and steel weight, and transfers mainly axial load to its own foundation.
Key facts
- Interior columns are commonly hot-rolled H-sections, tubes or built-up I-sections.
- They are usually pinned at both ends and carry mostly axial load.
- Column spacing across the width is set by use, typically matching aisles or production lines.
- Each column needs its own foundation, often a pad footing.
- Removing interior columns later is a major structural change and needs a new design.
Role in the structure
In a multi-span frame the rafter is continuous over one or more interior columns. Each interior column collects the reactions from the rafters on either side and carries them down to its footing. Interior columns are often pinned at top and bottom, so they act mainly in compression, while the exterior columns and rafter connections provide lateral stability.
When are interior columns a good choice?
For wide buildings where an obstruction-free floor is not essential, interior columns can reduce frame weight substantially. Warehouses with racking, factories with defined production lines and bulk stores often accept columns placed along aisles or between zones.
Where the use demands open space, such as hangars, sports halls or exhibition halls, a clear-span frame is preferred even though it is heavier.
How are interior columns placed?
Columns are aligned with the frame lines along the building length. Across the width, their positions are set by the owner's layout: racking bays, truck lanes, equipment or future subdivisions.
Jack beams can be used to omit an interior column at selected frame lines, creating a wider column-free zone. This option should be discussed at design stage because it affects adjacent frames.
How do interior columns connect to the frame?
The column cap plate typically bolts to the underside of the rafter, with stiffeners in the rafter web to spread the load. The base plate bolts to anchor bolts in the footing.
Because the connections are usually pinned, interior columns are simple to fabricate and erect, but they must be held plumb until the rafters are connected and braced.
Materials & coatings
- Hot-rolled H-sections or wide-flange shapes in structural steel grades.
- Square or rectangular hollow sections where a compact profile is preferred.
- Built-up sections for heavy loads.
- Primer, paint or galvanizing; impact protection in traffic zones.
Design considerations
- Axial load from roof, snow and collateral loads on adjacent spans.
- Slenderness and buckling length.
- Vehicle impact risk and need for bollards or guards.
- Fire resistance requirements for the occupancy.
- Alignment with racking, aisles and equipment.
- Future flexibility, including possible jack beams.
Fabrication
- Cut sections to length and weld cap and base plates square.
- Drill or punch holes to template for anchor bolts and rafter connection.
- Apply coating and mark pieces to frame lines.
Erection
- Set columns on leveling nuts and check elevation to the design top level.
- Brace temporarily until the rafter is placed and bolted.
- Check plumbness before grouting the base.
Inspection & quality
- Confirm cap plate elevation and alignment to rafter.
- Check bolt installation at cap and base.
- Verify column plumbness and protection where required.
What to include in your RFQ
- Acceptable interior column positions or no-column zones.
- Racking, aisle and equipment layout.
- Vehicle traffic and any column protection.
- Fire rating requirements.
- Future plans that may require removing a column.
3D model & IFC of this component
Rotate the model, isolate the component and download its IFC4 file for your BIM coordination model.
IFC entity: IfcColumn. Illustrative geometry for coordination and learning. Final member sizes come from the project design.
Frequently Asked Questions
How much steel do interior columns save?
Savings depend on span and loads, but shorter rafter spans usually reduce frame weight noticeably. The engineer can price clear-span and multi-span options side by side.
Can interior columns be round tubes?
Yes. Round or square hollow sections are used where appearance or a compact footprint matters, provided the connections are detailed for them.
Can an interior column be removed later?
Only after a structural redesign, usually adding a jack beam or strengthening the rafter. It should never be done without an engineer.
Engineering content is general guidance. Every World Steel building is designed by qualified engineers to the code and loads of the project.
