Metal Building Member Connections

By TimGary (****)

Date 11-23-2005 16:18

I was wondering if anybody would like to comment on the shimming of bolt connections of pre-engineered metal building frame members in order to compensate for slight irregularities in fit-up.

Is it OK to use flat washers on the bolts inbetween connection plates?

Should the connection plates be welded after shimming to hide the gap or for structural stability?

What is the maximum gap caused by shimming that you would allow?

Is this something that you would define as a common practice?

Any comments appreciated.
Tim

By G.S.Crisi (****)

Date 11-23-2005 18:42

Back in my days of erector engineer, what we did was the following:

1. Instead of a round, regular washer, we used a washer (a filling plate, if you prefer) made up from plate, with a hole in it through which the bolt passed. The thickness of the "washer" was the same as that of the gap and its dimensions (length and width) were the necessary to fill the area of the connection, or in other words, the area that the connecting plates were supposed to be one against the other.
If the "washer" was crossed by several bolts, of course we had to make holes also for them.

2. We didn't weld the connection plates.
3. The gaps that were "replenished" in this way were up to 1/4, or may be 5/16 of an inch, thick.

4. Back in my days of erector engineer I've erected hundreds of tons of structural steel and all of us know that there are always pre-fabrication irregularities (not to say defects) that must be corrected on the field in one way or the other. When erection is in progress you just can't order a new structural member and stop the work until it arrives to the site.

Giovanni S. Crisi
Sao Paulo - Brazil

By swnorris (****)

Date 11-23-2005 20:03

Tim,

From my understanding, pre-engineered metal buildings are designed to support only minimal loads. I would use finger shims to fill the gaps as opposed to washers. They are more common practice in structural applications, which have a safety factor with regard to loading designed into everything. No welding would be needed.