The process of installing a structural steel frame involves an orchestrated effort of various parts and pieces, the names of which can be confusing enough, let alone their process of assembly. As we go through the assembly of a conventional steel structure, we're going to identify the nomenclature of the various elements and what those tags represent. A structural steel frame starts with the base, where the columns of the frame attach to the foundation.
The columns are attached to the concrete foundation with anchor bolts, which are typically supplied by the steel fabricator for installation by the concrete contractor. These bolts come in various shapes and sizes, and the appropriate one will be identified by the project structural engineer. Because these bolts are embedded in concrete, accuracy of their installation is critical, obviously because they cannot be moved once the concrete is set. If their location is off, that means the rest of the structure is not going to fit together.
So, to help ensure proper spacing in the foundation, the steel fabricator will also supply setting plates with the anchor bolts. Now, once the anchor bolts are in place and the foundation is cured, the steel erector can begin installation of the superstructure. This process begins with installation of the columns. Columns can be fabricated from two different steel shapes, tube steel and I-beams. Tube steel columns are identified by the following marking, representing shape, physical size, and wall thickness of the material being used.
Like hollow structural columns, I-beams start their labeling with a letter, which identifies the beam's shape. The first number indicates its depth in inches, And the last number identifies the beam's weight per lineal foot. Now regardless of the shape, each column will have a base plate, in some form or fashion, for attachment to the anchor bolts, and connection points for the upper structural elements. During initial assembly, the columns are loosely attached on the anchor bolts to allow for easier assembly of the horizontal structural elements.
The horizontal structural pieces will consist mainly of I-beams. However, in certain areas, tube steel will be used for the horizontal elements. Tube steel is also commonly used for cross-sectional bracing within the framework. Just as with columns, the nomenclature for these pieces is typically the same.
In cases where the loads are not that extensive, such as canopies and beams over doorways, a steel channel may be used. Again, during installation these pieces will all be loose fit until the entire framework is together. Once assembled, the steel erector will go back and begin to plumb all the columns and square up the horizontal sections. As this is done, they will tighten up the connections and install any bolts that were left out during the rough assembly phase.
This makes the primary steel ready for assembly of the secondary support elements, which in most cases are bar joists. Bar joists are fabricated in various shapes and sizes, which we will discuss in another video. Each joist is typically tagged, identifying its manufacturer, sizing, and area of placement within the project.
As you can imagine with most projects there are a lot of different bar joists being used so knowing where within the project those joists fit make it much easier for the iron workers during installation. They can be installed using either a bolted or welded connection or a combination of both. As the joists are placed, lateral bracing is installed from joist to joist. which links them together creating a total system.
Now installation of the bar joist does not complete the framework of the structure. Although the connections have been secured, the frame still has the ability to move out of square. To eliminate this tendency, a corrugated metal deck is installed on top of the horizontal framework. The deck acts in the same manner as sheathing and floor decking does in light frame construction. It provides a medium to unitize the entire framing system, which will help eliminate the potential for lateral movement.
At the same time, it creates a support layer for the roofing and flooring. Now, once the deck has been installed, holding the frame in place, the iron workers can then go back and finish tightening and torquing all bolted connections and completing weld joints. This process is called detailing the steel and this completes the installation of the system. Now we've only just scratched the surface here of what's involved in structural steel frame construction, but what you have is a good base knowledge that's going to get your mind thinking and start generating questions that are going to increase your knowledge of this type of construction.