Structural Steel

Important Roles Of Bolts For Structural Steel Frameworks

Bolts are important components of a structural steel framework. Bolts are used to fasten connecting elements like framing angles and gusset plates to the connected parts such as beams and frames.

Bolts Commonly Used For Bolting Structural Steel Frameworks

Currently, the specifications of the American Institute of Steel Construction (AISC) cover two types of bolts for bolting structural steel building connections. These are the common bolts and high-strength bolts.

Common bolts or A307 bolts are the most affordable types of structural bolts. However, their applications are restricted because of their low carbon content. Bolts containing low carbon are not recommended for high-stress situations.

Common bolts are rather used for non-critical connections, such as fastening secondary structural members. Examples of secondary structural members are purlins, girsts, stairs, or platforms.

On the other hand, high-strength bolts are used for a majority of field bolted connections primarily because of their stronger performance. High-strength bolts are either made of high-strength carbon steel or high-strength alloy steel.

Structural Steel: From Anchor Bolt To Anchor Rod

The AISC changed the term anchor bolt to anchor rod to refer to material specifications for steel-to-concrete applications. In the past, it was too common to mistakenly assign materials for steel-to-steel bolting applications that were actually for steel-to-concrete applications.

The usual material specification for steel-to-concrete applications is ASTM F1554. It is a relatively new material specification for hooked, threaded, headed, and nutted anchor rods. Several other specifications can also be used for anchor rods. The A193 type, for instance, is used for applications requiring unheaded rods.

The length of embedment of the anchor rod into the concrete can be determined by engineers or designers who follow the ACI or American Concrete Institute. It can also be accomplished in structural offices using office standards based upon the diameter of the rod.

Determining the length of the rod to be embedded into the concrete is necessary in order to develop sufficient bond stress. So the larger the rod diameter, the greater the expected stresses are likely to be and the deeper the anchor rod must be embedded into the concrete.