When we think about steel structures, massive columns, beams, and steel plates often come to mind.
Yet, one of the most essential components is also the smallest — the bolt.
These small but powerful fasteners are what hold the entire structure together, ensuring strength and stability for decades.
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What Are High Strength Bolts?
The bolts used in steel structures are not ordinary bolts.
They are known as High Strength Bolts, made from special alloy steel capable of withstanding extremely high tension and compression forces.
Common grades include A325 and A490, or their metric equivalents Grade 8.8 and Grade 10.9.
Each bolt is installed with a nut and a washer, which help distribute the load evenly and protect the steel surface from damage during tightening.
Controlled Tightening and Torque Accuracy
High strength bolts must be tightened using a torque wrench that applies a precisely measured amount of force.
In modern projects, engineers often use TC Bolts (Tension Control Bolts) — an advanced type of bolt that features a tail section designed to snap off automatically once the correct tension is achieved.
This system ensures a quick, accurate, and reliable installation.
Types of Structural Connections
High strength bolts are used in two main types of steel connections:
- Bearing Type Connection
In this type, the load is transferred through the bearing contact between the bolt shank and the hole wall.
It is typically used in joints with lower dynamic loads. - Friction Type (Slip-Critical) Connection
Here, the bolt is tightened to a very high tension, creating friction between the connected plates that prevents any slip or movement.
This method is the safest and most reliable, especially in bridges, factories, and large steel hangars.
The Importance of Choosing the Right Bolts
Selecting the proper bolt type is not a minor decision — it is a critical part of structural design.
Each project requires bolts with specific grades and strengths depending on load conditions, connection type, and environmental factors.
Using incorrect or low-quality bolts can lead to connection failure or structural instability over time.
At Hasanoglu Steel Structures
At Hasanoglu, we pay meticulous attention to every detail of our steel structure projects —
from the engineering design and fabrication processes to the careful selection of high-strength bolts for each connection.
We believe that structural strength begins with small details,
and that’s why we adhere to the highest international standards to ensure durability, safety, and precision in every project we deliver.