Engineering Strong Connections: The Integration of Steel Cleats with SHS Columns in Structural Design

 

In modern structural steel design, the emphasis is no longer just on the strength of individual members, but also on how these elements are connected. In buildings that use SHS columns (Square Hollow Sections), the cleat steel connection has become an essential solution—balancing strength, simplicity, and constructability.

This article explores the engineering principles behind steel cleats, their role in optimizing connections with SHS columns, and how they contribute to safer, faster, and more efficient structural systems.

The Structural Appeal of SHS Columns

SHS columns are widely used in structural applications for their:

  • Geometric efficiency – Square cross-sections provide excellent symmetry.

  • Aesthetic appeal – Clean lines are favored in architectural designs.

  • High strength-to-weight ratio – Ideal for multi-storey buildings and lightweight construction.

  • Resistance to buckling – SHS columns resist local and global buckling better than some open sections.

However, SHS columns are closed profiles, which poses a design limitation—internal access is restricted, making traditional through-bolt connections impossible. This is where steel cleats come into play.

What Is a Steel Cleat?

A steel cleat is a plate or bracket made from structural steel that connects one steel member to another. In SHS column applications, steel cleats are either welded or bolted to the exterior face of the column, providing a base for connecting beams, braces, or other structural components.

Typical Properties:

  • Material: Usually mild steel or high-strength structural steel (S275, S355).

  • Thickness: Varies by application, generally 6mm–20mm.

  • Connection type: Bolted, welded, or hybrid (welded to column, bolted to beam).

How Steel Cleats Work with SHS Columns

Cleat steel allows external components to connect to SHS columns via face-mounted connections. Since SHS sections lack accessible flanges or web areas (like an I-beam would have), cleats serve as the interface.

This setup provides several mechanical advantages:

  • Shear force transfer between beams and columns.

  • Moment resistance, depending on cleat size and bolt placement.

  • Torsional stability when used in bracing or truss connections.

Common Cleat Applications in SHS Frames:

  • Beam-to-column connections (cleat welded to SHS column face).

  • Bracing-to-column joints (gusset plates acting as cleats).

  • Secondary steel attachment, such as purlins or cladding rails.

Engineering Design Considerations

Properly designed steel cleats must accommodate the structural loads and tolerances required by the system. Key design parameters include:

1. Load Path and Force Transfer

  • Cleats must carry and transfer loads from one member to another efficiently.

  • Bolted cleats must consider shear, tension, and bearing forces.

2. Edge Distance and Hole Spacing

  • Bolt hole positioning must comply with codes (e.g., Eurocode 3, AISC).

  • Too close to the edge can lead to tearing or splitting; too far reduces compactness.

3. Weld Size and Type

  • Fillet welds are commonly used to attach cleats to SHS columns.

  • Full penetration welds may be required for high-moment connections.

4. Connection Ductility

  • Ductile behavior ensures the structure redistributes loads before failure.

  • Cleats may be designed as “fuse” elements in seismic regions to absorb energy.

Standards and Codes

Designing steel cleats for use with SHS columns requires adherence to regional and international standards. Some key references include:

  • Eurocode 3 (EN 1993-1-8) – Design of joints and connections in steel structures.

  • AISC Steel Construction Manual – US standards for bolted and welded connections.

  • AS/NZS 5131 – Australian code for structural steel fabrication and erection.

Designers must also consider tolerances, fire rating requirements, and corrosion protection, especially for outdoor or coastal projects.

Advantages of Steel Cleats in SHS Column Systems

1. Installation Efficiency

Pre-welded cleats on SHS columns allow for rapid on-site bolting. This reduces the need for field welding, which is labor-intensive and weather-dependent.

2. Precision in Prefabrication

Cleats can be installed with CNC-machined accuracy in fabrication shops, ensuring tight fit-up and less alignment hassle on-site.

3. Cost Effectiveness

Simple geometry, standard plate sizes, and fewer man-hours required on site contribute to lower overall construction costs.

4. Adaptability

Cleats accommodate vertical or horizontal members, angled braces, and off-axis connections, making them versatile in layout-heavy projects.

5. Safety

Bolted cleat connections minimize the risks associated with hot work (welding) on site. This is especially important in high-risk environments like chemical plants or refineries.

Real-World Applications

1. High-Rise Construction

In tall buildings, SHS columns are often used for their aesthetic and structural advantages. Steel cleats make connecting floor beams to these columns much simpler and faster.

2. Industrial Sheds

Heavy-duty SHS columns form the primary frame in warehouses and manufacturing plants. Cleats are used to connect gantries, trusses, and crane rails.

3. Infrastructure Projects

SHS columns combined with cleats are used in airport terminals, train stations, and bridges, where fast installation and structural clarity are key.

4. Temporary Structures

In stadiums, exhibitions, or military bases, cleats allow modular, demountable systems to be assembled and disassembled with ease.

Innovation: Hidden Cleats and Architectural Detailing

For high-end architecture, visible steel cleats may not be desired. Innovations such as:

  • Recessed cleat pockets

  • Flush-mounted bolts

  • Custom-fabricated cleats to match façade lines

…have enabled architects to use SHS and cleat systems even in exposed designs, blending structural rigor with visual elegance.

Conclusion

The integration of steel cleats with SHS columns is a critical detail in modern structural engineering. What may seem like a small component—just a plate of cleat steel—can dramatically influence the efficiency, safety, and success of an entire project.

From industrial-scale buildings to cutting-edge architectural works, the humble steel cleat allows SHS columns to connect cleanly and powerfully with the rest of the structure. When properly engineered and applied, cleats offer unmatched speed, versatility, and strength—making them indispensable in the steel construction toolkit.

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