In structural steel construction, columns are critical components. These vertical members carry the weight of the structure above, floors, roofs, and any applied loads, and transfer them safely to the foundation below. Whether you’re designing a small commercial structure or a multi-story tower, understanding columns is essential to ensuring safety, stability, and efficiency.
What Are Structural Steel Columns?
Structural steel columns are vertical compression members that form the backbone of a building’s load path. They are designed to carry vertical loads from beams and braces and transfer these forces to the footings or foundation walls. These members must be accurately fabricated and erected to maintain structural integrity throughout the lifespan of a building.
Common wide-flange (W-shape) column sizes include W8, W10, W12, and W14. While heavy columns are typically mill cut to bear, lighter ones may be square cut at the bottom. The cutting type often depends on design drawings or fabricator preferences.
Types of Columns
Depending on the structure’s size, load conditions, and architectural considerations, various types of steel columns may be used:
- Wide-flange (W-shape) columns: These are the most common and efficient shapes for vertical loads.
- Built-up columns: Fabricated by welding plates to form custom sections for larger loads or special requirements.
- Box columns: Often created using plates welded to form a square or rectangular cross-section, suitable for high-load applications or aesthetic design.
- Laced and battened columns: Used when multiple shafts are joined with lacing bars or plates to act as a single unit.
- HSS (Hollow Structural Section) columns: These include round, square, and rectangular profiles. Their closed shape provides torsional resistance and a sleek appearance.Each type has its own application depending on strength, stiffness, architectural appeal, and construction method.
Each type has its own application depending on strength, stiffness, architectural appeal, and construction method.
Column Splice
As building heights increase, so does the need for column splices—the connections that join two or more column segments vertically. Splices are primarily needed due to:
- Length limitations of prefabricated steel sections.
- Load variation across floors requiring different column sizes.
- Ease of transportation and erection, as handling smaller column sections is more practical.
Splice designs depend on alignment, load transfer requirements, and construction needs. They can involve butt plates, fillers, and flange plates to ensure continuity and proper load distribution between segments.
Key considerations for splicing:
- Aligning column sections to ensure full bearing.
- Providing adequate welding or bolting for secure load transfer.
- Accommodating floor and beam connections without interference.
- Complying with OSHA safety regulations (e.g., splice height requirements on perimeter columns).
HSS Columns
HSS (Hollow Structural Section) columns are a modern alternative to traditional wide-flange shapes. These closed sections, which come in square, rectangular, and round profiles, are commonly used in schools, offices, and architecturally exposed structures.
Their uniform geometry allows for efficient axial load distribution and a clean appearance. However, their closed shape poses challenges for beam connections. As such, connections are typically fabricated in the shop, where plates, angles, or seats are welded to the HSS face. During erection, beams with end plates are bolted to these pre-welded fittings, minimizing field welding.
HSS columns are also favored in low- to mid-rise buildings due to their smooth profiles and efficient use of steel.
Engineering Design Data: What the Detailer Needs
The structural design drawings are the primary source of information for column detailing. These include:
- Plan views, elevations, and sections to show size and placement.
- Enlarged details for complex areas like stairwells or corners.
- Notes and tabulations indicating connection types, required welds, and bolts.
Column connections may also need to resist lateral loads (e.g., from wind or seismic events). These special requirements are often called out with specific symbols or keyed notes.
Column Schedules: Organizing Vertical Information
A column schedule organizes critical information about column types, sizes, lengths, and splice elevations. It’s a reference tool for fabricators and erectors to plan material preparation and sequencing.
Typically, columns are identified by a grid system (e.g., column D4 is at the intersection of gridline D and 4). Schedules often include:
- Column sizes per floor or tier.
- Splice elevations and cut-off points.
- Notes on floor framing heights and special conditions.
Column splice placement also affects erection cost and logistics. For example:
- Lower splices reduce the weight and cost of heavier bottom tiers.
- Splices must avoid conflicts with beam connections or bracing.
- Splice height should make safe erection practical without additional scaffolding or risky procedures.
Column Anchor Rods and Safety Considerations
Each column must be anchored to its foundation with a minimum of four anchor rods, capable of resisting at least 300 pounds of load (to support an erector and tools). Placement and spacing of these rods are influenced by the size of the column base and must account for ease of field alignment.
Safety cable attachments are also critical; especially for perimeter columns. These must support safety lines at 21 and 42 inches above finished floor level. It’s the fabricator’s responsibility to ensure these provisions are in place before delivery to the job site.
Steel columns are the backbone of structural stability in any steel-framed building. Whether it’s selecting the right type of column, detailing efficient splice locations, or accounting for safety requirements during erection, each decision plays a crucial role in ensuring a strong, safe, and cost-effective structure.
By understanding how columns function and how they’re detailed and erected, fabricators, engineers, and detailers can work together more effectively, building smarter and safer structures every time.
