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RE: washers and oversized holes and TC bolts

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Title: RE: washers and oversized holes and TC bolts

>The fabricator used 7/8" dia holes for the 3/4"
>bolts to take care of the galvanizing.  (As an
>aside, I have heard from the American Galvanizers
>Association that oversizing the hole for galvanizing
>is not required, but some erectors have told me
>differently - I am not sure who is correct.)

AGA is correct. There is nothing in the AISC or RCSC Specifications that permits the increase that a lot of people seem to think you can take in hole size when galvanizing is specified. The maximum hoe sizes remain unchanged, even for galvanized steel. You'll now have to treat that hole as an oversized hole because it exceeds the maximum hole size permitted for a STD hole.

>Anyway, now the question is "Do we need to put a
>washer on the head side of the TC bolt because it is
>an oversized hole (I think the answer to this is yes,
>but since it is not really a standard oversized hole,
>I was not sure).

It depends. Most TCs have a head size that is already washer-sized. If so, you do not need to add a washer under the TC head. If you have a TC that does not meet this you will have to add a washer.

>If we do add the extra washer, does it have an affect
>on how the TC bolt functions?

No, I don't think it will make any difference.