TB vs TF Bolt Connections – What’s the Difference and Why It Matters

In structural steel connections, selecting the appropriate bolt type goes beyond size and strength — it requires a clear understanding of how the bolt behaves under load and during installation. One common area of confusion for many engineers and site teams is the difference between TB and TF bolts.

What Are TB and TF Bolts?

Both TB and TF bolts fall under the category of High Strength Friction Grip (HSFG) bolts, widely used in critical structural connections. These bolts are engineered to create sufficient friction between connected steel plates, enabling load transfer without slip.

The key distinction lies in their installation method and function, which defines whether they are TB or TF bolts.

🔩 TB – Tension and Bearing

TB stands for Tension Bolt.

• Designed for bearing-type connections, where load transfer occurs through friction created by bolt tension.

• These bolts are tightened to a specific tension, usually by the turn-of-nut method or a calibrated torque wrench.

• The friction between the steel plates resists the load — not the bolt bearing directly.

• Commonly used in:

  • Rigid connections

  • Bolted splices

  • Applications where slip under serviceability loads is unacceptable

    

    
    

🔩 TF – Tension and Friction

TF stands for Tension-Fastening.

• Also known as Friction Grip Bolts, these are used in slip-critical connections.

• TF bolts are fully tensioned to a predefined load.

• Load transfer is achieved through friction between contact surfaces, preventing slippage under service conditions.

• Typical applications include:

  • Bridges

  • High-rise buildings

  • Structures where movement is not permitted

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Why the Distinction Matters

Choosing between TB and TF bolts isn’t a matter of preference — it’s a matter of structural requirement. Key considerations include:

1. Load Characteristics – Is the load dynamic or static?

2. Connection Quantity – Are there numerous or repetitive connections?

3. Installation Efficiency – What’s the required speed of assembly?

4. Surface and Environmental Conditions – Is the steel surface treated, painted, or exposed to corrosion?

   
   

Conclusion

Selecting the correct bolting method can significantly impact:

• Structural integrity

• Long-term performance

• Maintenance needs

• Installation efficiency

Understanding the roles and requirements of TB and TF bolts ensures safe, durable, and code-compliant steel connections. Making informed choices based on design expectations and site conditions is essential for achieving optimal performance in any structural project.