PDB Debrief: Structural Steel Fasteners

May 2022

While perhaps obvious, the bolts and fastening of structural steel are integral to the construction of a building. They are literally the lynchpin in the ability for the building to stand. Because these connections are critical, it is imperative to use the right fastener for the application and materials involved.

Types of bolts and their application is very important to a proper connection in structural steel. Bolts are made from various grades of steel and types of steel depending on the application. Grades would include A325, A490, and iterations such as A325S. Structural bolts, washers and nuts will have markings on them showing the grade, but also other identifying marks such as manufacturer.

Bolts can also be made of Stainless Steel, galvanized, weathering steel, and other types of steel, again, it is important to be sure the correct bolts are being used for the application, and being installed correctly. It may seem obvious how to install a bolt, but there are judgment calls to be made on proper tightening or tension for the bolted connect. There are specialty bolts designed to remove the need for this kind of judgment, but they must also be appropriate to application.

The type of connections will often dictate the type of bolt to be used. Connections types include snug tight, pretensioned and slip critical. For pretensioned and slip critical, special bolt configurations are made such as ‘tension control bolts’ (TC) and ‘load or direct indicator washers’ (DTI).