Primary Framing
Tapered Columns in Pre-Engineered Steel Buildings
Definition: A tapered column is a built-up steel I-section whose web depth increases from a shallow base to a deep knee. It forms the vertical leg of a rigid frame, carrying axial load and the bending moment that peaks at the eave connection.
Key facts
- Web depth varies linearly along the column, shallowest at the base.
- Flanges, web and end plates are welded from separate plates.
- The inner flange is stabilized by flange braces connected to girts.
- Columns may carry crane brackets, mezzanine beams or canopy connections.
- Base depth is often kept small to suit pinned bases and compact pedestals.
Role in the structure
The tapered column receives the rafter end moment, shear and axial force at the knee and carries them down to the base plate. Because a pinned base attracts little moment, the column can be shallow at the foundation and deep at the top, matching section depth to demand. The column also supports wall girts, which in turn brace its inner flange through flange braces.
Why use a tapered column instead of a uniform section?
In a pinned-base portal frame the moment at the base is near zero and grows to a maximum at the knee. A uniform column would have to be deep along its full height to cope with the knee moment, wasting steel near the base.
Tapering removes that excess. It also produces a slender base that fits narrow wall zones and keeps anchor bolt groups compact, which can simplify the foundation layout.
Where are tapered columns used?
Tapered columns form the exterior legs of most clear-span and multi-span rigid frames. Where loads are heavy, such as with top-running cranes, the column may become stepped or include a separate crane leg.
Uniform-depth columns are still used where a constant depth suits the architecture, for instance to keep a straight interior face for racking, or where a fixed base produces significant base moment.
How is a tapered column checked for stability?
Slender plate girders can buckle locally or laterally. The engineer checks web and flange slenderness, provides stiffeners where concentrated loads enter, and relies on girts and flange braces to restrain the inner compression flange at intervals.
The governing code sets the methods; the design must also account for the variation in section along the length, which modern frame design software handles directly.
Materials & coatings
- Structural steel plate for flanges and web, grade selected by design to the project code.
- Hot-rolled sections where a constant-depth column is more economical.
- Shop primer, paint systems or hot-dip galvanizing according to exposure.
Design considerations
- Knee moment and axial load from the rafter and roof loads.
- Lateral drift under wind or seismic loads.
- Concentrated loads from crane brackets, mezzanines or canopies.
- Flange brace spacing aligned with girt positions.
- Base depth compatible with pedestal and anchor bolt layout.
- Clearance between columns and interior equipment or racking.
Fabrication
- Web plates are profile-cut to the tapered shape and flanges cut to width.
- Plates are fitted and joined with continuous fillet welds on automated lines.
- Base plate, cap or knee end plate and stiffeners are welded to the shop drawings.
- Holes for girts, flange braces and bracing are punched or drilled before coating.
Erection
- Set the column on leveling nuts or shims over the anchor bolts.
- Plumb and temporarily guy or brace the column until the rafter is connected.
- Install girts and flange braces before final alignment.
- Grout under the base plate after the bay is plumbed and bolted.
Inspection & quality
- Check overall length, depth at base and knee, and hole positions.
- Inspect flange-to-web welds as required by the quality plan.
- Check plumbness after erection and before grouting.
- Repair coating damage from handling.
What to include in your RFQ
- Eave height and any clear height required at the inner flange.
- Wall cladding system and girt arrangement.
- Crane, canopy or mezzanine loads to be carried by columns.
- Preferred base condition if the foundation design is already fixed.
- Coating system and environment.
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
Do tapered columns cost more to fabricate?
They require cutting and welding, but on automated lines the extra effort is small and is usually offset by the steel weight saved compared with uniform sections.
Can racking be placed against a tapered column?
Yes, but the sloping inner flange must be accounted for in the layout. If a straight interior face is needed, tell the engineer early so a constant-depth or outward-tapered column can be considered.
Are tapered columns suitable for cranes?
Light cranes are commonly supported on brackets welded to tapered columns. Heavier cranes may need stepped columns or separate crane columns, as confirmed by the engineer.
Engineering content is general guidance. Every World Steel building is designed by qualified engineers to the code and loads of the project.
