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RE: Steel column tolerances

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Title: Steel column tolerances
>I am working on a three story steel building that has columns that are
>broken at each floor level to allow for cantilevered beams to extend
>"through" the columns.  The steel detailer asked me the question of whether
>he should allow for shim plates between the column and cantilevered beam
>to the tolerance of +/- 1/8" on the beam depth.  That seemed reasonable to
>me, but the erector claims that he can not be expected to shoot elevations
>of the steel and install to a set elevation.  Can anyone point me towards a
>reference that gives erection tolerences related to building framing
>elevations?  Does the shim plate requirement seem out of the ordinary?

Your detailer is a real prize as most people would not even think of this very real potential problem until it was staring them in the face on the job.

Tolerances for steel erection are in the AISC Code of Standard Practice, but there is nothing in there that covers this special case. I have seen this before when a column lands on a steel transfer girder -- same basic issue. I do have to say that it is unconventional to cut columns to do cantilevered beams continuous. Not impossible, but you have discovered one of the issues.

With the lack of a tolerance specified you can either decide that tolerances don't matter for this case and it can wind up where it will, or that a tolerance is necessary. If you decide the latter, you will have to specify what tolerance(s) you want. Perhaps the tolerances for column bases will give you some guidance. Ultimately, I suggest it would be good to meet with the detailer, fabricator and erector to determine what can be done to hold the positions and alignment you decide must be met.

Hope this helps.

Charlie