In the design and construction of steel structures, bolted connections are crucial for structural safety, stability, and cost-effectiveness. Faced with a wide variety of bolt types, choosing the right one between high-strength and common bolts is essential knowledge for every engineer, project manager, and construction worker. Choosing the wrong bolt can impact construction efficiency at best and create serious safety hazards at worst.
This article will deeply analyze the core differences between high-strength and common bolts, providing a scientific and reliable selection guide.
I. Essential Differences: Fundamental Differences in Working Principles
This is the cornerstone for understanding all the differences between the two.
Common Bolts:
Working Principle: Force is transmitted through shear resistance in the bolt shaft and pressure from the hole wall. The connection relies on close contact between the bolt shank and the hole wall. When slippage occurs on the connecting surfaces, the bolt shank is subjected to shear forces and pressure from the hole wall.
Force-bearing Characteristics: The bolt has minimal internal pre-tension, and the friction generated when the nut is tightened is negligible. External forces are directly borne by the bolt shank itself.
High-Strength Bolts:
Working Principle: Force is transmitted through friction. Their core principle is to apply a significant pre-tension (precisely controlled using a torque wrench) to tightly clamp the connected steel plate bundles together, generating significant friction at the contact surface.
Load-bearing Characteristics: External forces are primarily borne by friction at the contact surface. Only when the external force exceeds the maximum static friction does relative slip occur between the connection surfaces, at which point the bolt shank begins to contact the hole wall and bear pressure.
II. How to Choose the Right Bolt?
Choose High-Strength Bolts:
Structures subject to dynamic or repetitive loads, such as crane beams, bridges, and stadiums, utilize their excellent fatigue resistance.
Major load-bearing joints and critical connections, such as beam-column connections, column base joints, and support connections, require high joint rigidity and minimal deformation.
Choose Ordinary Bolts:
Secondary connections are subject to static loads, such as walkway slabs, staircases, and decorative structures.
For temporary fixing and positioning during installation. Connections primarily bearing tensile forces (calculations are required to confirm their grade meets the requirements).
In short, high-strength bolts are the "muscle" of a load-bearing structure, while standard bolts are the "ligaments" connecting non-critical parts. Understanding their essential differences and following a standardized selection process are key to ensuring the long-term stability of steel structures.
