We will start with the start. I have always heard that you have to start with a solid foundation, that is even Biblical. You know? I have always started with the foundation page first to find all of the column locations. You often have to reference a column schedule, or even the roof plan to determine the size of the columns, but for today we will concentrate on the parts of the column that will need to be included.
In the detail above you will see a typical column. This can be a Tube Steel, Wide Flange, or even a Pipe column. Rarely it can even be a channel or angle, the material used is as limitless as the Architect and Engineer’s imagination. Today we will assume it is a Tube Steel. You will see the different parts that need to be included are colored. The individual parts are as follows:
Base Plate (blue) – the base plate is a plate (simple enough) welded to be bottom of the column used to attach the foundation to the column. This can be a plate of almost any size or thickness. I have had 3/8″ thick base plates to over 3″ thick! They can weigh anywhere from a few pounds to several hundred depending on the loading and bracing that are required. Will typically be a minimum of 6″ longer and 6″ wider than the column, to give spacing for the anchor bolts.
Anchor Bolts (orange) – the anchor bolts are actually what connects the foundation concrete to the column. They are various lengths and diameters and are embed into the concrete when the foundation or pier is poured. Typically they will have washers and nuts to attach the base plate. These will be ordered and delivered to the job-site early, when the foundation and slab concrete are being poured, which is usually several weeks ahead of the arrival of the steel.
Column (green) – this is the column itself. The main part of the main part. There are a huge range of sizes and shapes that can be used, all determined by the needs of the owner and the engineer. The height will usually be from the top of the pier to the bottom of the deck, minus: the thickness of the base plate, the depth of the joist girder seat (the part of the joist girder that bears on the column’s cap plate), minus the thickness of the cap plate. So the column will be somewhere around 6″-7″ shorter than the distance from top of pier to bottom of deck.
Cap Plate (yellow) – the Cap Plate is what the joist girder bears on and is attached to. The Cap Plate is usually a minimum of 6″ longer and 1″ wider than the column for bolt attachments. The joist girders are bolted to the cap plate during the erection phase and then welded for permanent attachment.
Stabilizers (red) – the Stabilizers slide between the bottom chords of the joists and the joist girders. They are shop welded to the column, but are not welded to the joists or joist girders. They are principally to keep the joists and joist girders from rolling or rocking. They are not welded or affixed to the joists and girders to allow for expansion and movement of the building.
The column, base plate, cap plate, and stabilizers are welded together in the shop and will ship to the job-site as a complete unit. It will be the responsibility of the detailer to make sure the lengths are perfect. For the estimator, we need to make sure we are as accurate as possible for our bid, but also note that some material for the columns will not be acquired in the exact length. Much of the time the column will need to be ordered in a length that is available, not the exact length that is required. For example, if our column needs to be 38′- 7″, it is not likely that we can order the material in that exact length. We would have to order it in a 40′- 0″ length and cut it down in the shop. This would have to be accounted for in the purchasing and on our estimate.