What is the purpose of high-strength bolts in structural steel connections?

• A. To replace welding entirely.
• B. To allow for easy disassembly.
• C. To be used only in non-structural elements.
• D. To create high-strength connections that require pretensioning for slip-critical.

Answer: (D)

High-strength bolts are used to create high‑strength connections that are pretensioned to achieve slip‑critical behavior. When these bolts are tightened to a specified tension, the plates being connected are clamped tightly together. That clamping generates friction at the contact surfaces between the plates, so the joint resists shear not primarily by the bolt shearing or bearing alone, but by the friction of the clamped surfaces. In slip-critical connections, this pretensioning is essential because it prevents the members from sliding relative to each other under load, ensuring the connection transfers forces reliably.

This is why the concept focuses on pretensioning to achieve slip-critical action: the goal is a robust, high‑strength connection that remains stable under service loads. Bolts aren’t intended to replace welding in every situation, nor are they exclusively for non‑structural elements. They provide a controlled, high‑strength means of fastening when slip resistance is critical, and their installation methods ensure the required clamping force is achieved.