Structural Bay
CSI Division 05, Metals
A rectangular section of a building's structural frame bounded by a set of columns on each side, the basic repeating unit a steel or concrete frame is built from, one bay at a time, across the whole structure.
Why it matters
This is a construction term of art, not the everyday meaning of "bay" as a body of water, and it's the unit a steel erection crew actually thinks and plans in: once one bay's columns, beams, and bracing are plumbed and connected, the crew moves on and repeats the same sequence in the next bay across the building.
On a real project
A steel erection crew fully plumbs, aligns, and permanently bolts up every connection in one structural bay before moving the crane and crew to erect the next bay over, rather than setting loose steel across the whole building before finalizing any of it.
Who this matters most to
An Ironworker thinks of steel erection in terms of bays, since a crew typically can't move on to permanently connecting the next bay until the current one is fully plumbed and squared.
Where this goes wrong
A crew sets steel loosely across several bays at once to keep the crane moving efficiently, planning to go back and plumb and finalize each bay afterward. Without one bay locked into its final, true position first, errors compound across the loosely set bays and become much harder to track down and fix.