1- Easy introduction to bolted connections.

Last Updated on August 26, 2026 by Maged kamel

Introduction to Bolted Connections.

The brief content of the post for the bolted connection.

These are the items to be discussed in this post: The first point, with God’s will,  is the bolt types; there are two types: the first type is low-carbon steel, and the second type is high-tensile steel bolts, which are the most used types of connections and can be classified into two types: ASTM A325 and A490.

The second subject is the bolt’s structural dimensions, length, and the names of its components.
The third subject is the related chapter in the AISC concerning connections.

The first material we have is ASTM A-307 low-carbon steel, used in secondary structures such as handrails, light stairs, service platforms, and similar structures not subject to cyclic loads.

These structures have loads that remain constant over time. Unfinished bolts have a lower load-carrying capacity than high-strength bolts, so bolts, due to lower capacity, are used in secondary structures, which have a lower load capacity acted upon by lighter loads. The second subject is high-strength bolts.

These bolts can be classified into two categories according to the ASTM specifications for high-strength bolts. We have ASTM A325 & ASTM A490. The non-high-strength bolt is ASTM A307, which we discussed earlier.

The high-strength bolts are made from medium-carbon, heat-treated steel and have a tensile strength much greater than that of ordinary bolts. The strength of these bolts is much greater than that of ASTM A307 bolts.

The different components of High-strength bolts for bolted connections.

For the shape of bolts. I quote that high-strength bolts are the most common type of bolt used in steel structures and have more than twice the tensile strength of unfinished bolts.

This is a sample of ASTM A325 from one of the suppliers; it is marked on the head with the symbol U for unfinished.

The second bolt sample is for the ASTM A490 bolt. Again, it is written on the head with the ASTM A490 symbol.

I quote that these ASTM A490 bolts are very commonly used in steel construction where large loads are transferred. They have higher strength than ASTM A325 bolts, so fewer may be required if connection strength is limited by bolt strength.

This is the advantage of using a higher-strength bolt, which minimizes the number of bolts required for the connection.

This section addresses the types of bolts and their components for bolted connections. This is the head of the bolt with a shank, which is the smooth part of a fastener above the threads, followed by a thread.

This is the washer shown in the two sections that follow. The next part is the nut. Here again, we see the washer and nut on the threaded portion.

The bolt length can be divided into two parts: the first part is the head, the shank, and part of the thread till the washer.

This is called grip. The threaded part is shown in the sketch; the bolt’s total length is the shank plus the threaded length. The washer diameter is specified as 1.65D. It is written: body diameter E, as in thecut-theread picturepicture; lengths of the round portion. H is the head height. The thread length is Lt. The transition thread length is Y, as shown here in the picture. G is the width across corners.

Classification of the High-tensile bolts according to section J3 for bolted connections.

What about the chapter that deals with the design of connections in the AISC? It is Chapter J. If we need to check the welded connection, the relevant section is J2.

High-strength bolts for bolted connections.

In Chapter J- Part J3, Bolts and threaded parts at item 1, the code describes high-strength bolts and classifies them into Group A and Group B.

A325 bolts fall under Group A.

If, in a given problem, it is mentioned that the bolt is of Group A. Then, it is the ASTM A325 bolt. If he wishes to include bolt ASTM A490, then it falls within the group.

Additionally, there are two categories: whether threaded connections are included or excluded for bolted connections. This other classification will be discussed in God’s will next time. What about snug, tight, and fit?

The snug-tight bolts for a bolted connection.

As we can see in the picture, the bolts in the base plate are placed and need to be tightened. There is an intersection of two angles. This is a Structural part, possibly a pedestal, but it is unclear.

Then tightenings by spanner, which is a spud wrench, which is an open-ended wrench approximately 16″ long. So, the torque produced by the spud tightens the bolts.

There is another method known as pre-tensioning. This type of connection is called a shear connection. I quote: The snug-tight can be specified as a shear connection or a tension-only connection.

The snug-tight method is not permitted for connections supporting non-elastic loads, nor is it permitted for ASTM A 490 in tension.

This is the PDF file for the content of this post, which can be viewed or downloaded from the following button.

This is a very useful source for the design of various steel elements: A Beginner’s Guide to the Steel Construction Manual, 15^th ed, Chapter 4 – Bolted Connections.

This is a very useful source for the design of various steel elements: A Beginner’s Guide to the Steel Construction Manual, 16^th ed, Chapter 4 – Bolted Connections.

The following ppartton Bearing Type connections -part,,-1- discusses the types of bearing bolts.- Types of failure for the bolted joint.