RE: Grade @ Anchor Bolts[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
- Subject: RE: Grade @ Anchor Bolts
- From: Charlie Carter <carter(--nospam--at)aiscmail.com>
- Date: Thu, 17 Aug 2000 10:44:48 -0500
>I have generally overcome the A307 availability issue by specifying A36
>threaded rods with a nut at the embedded end (as opposed to a bolt head).
>AISC recommends a different ASTM (Charlie?) whose number eludes me at the
>moment. Last time I mentioned it to the largest local steel service center
>(AFCO Steel), they didn't know what I was talking about. They had to call
>their bolt supplier.
Your practice is viable, but keep your eye on that new spec ASTM F1554 because it will gradually become the default standard for anchor rods. It's a great spec, written in large part by the late John Botts, who solved a lot of anchorage dilemnas for his customers over the years. Read more about it here:
>Also, AISC recommends bolt hole diameters in base plates that cannot
>realistically work with standard bolt heads or nuts, so I recommend using nuts
>and plate washers with standard holes on both sides of the base plate.
The reasoning for the new base plate hole diameters is covered here:
You definitely need a plate washer under the nut with these hole sizes. But then again, the old hole sizes were also such that you probably should have allowed for the use of plate washers with those sizes too, though.
>Finally, I have difficulty accepting that a nut or bolt head is sufficient for
>the embedded end of an anchor bolt loaded in tension, so I add a plate there as
If you look at the details of the research that is referenced in the 2nd Edition AISC LRFD Manual (see Part 8, where anchor rods are covered) and in related ACI documents, you'll find that headed or threaded/nutted embedments can be fully developed with the head/nut only by selecting the proper embedment (length). Actually, the results indicated that adding a plate at the bottom of the embedment introduced a plane of weakness in the concrete that REDUCED the strength of the embedment!
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