[TowerTalk] FW: Base Anchor Bolts

[Mike Fahmie]

Thanks for all of the feedback on my anchor question.

My HDX-572 was manufactured around 2001 but never erected.  I bought it from an SK's estate without doc's.  Evidently this was before their anchor design became more conservative since the 6 provided anchor bolts are type C (welded nut, no washer/plate).  The SAR that UST sent me (dated Aug 2009) was also calculated with just a welded nut.  My bolts are 1"x27" for about 21" of embedment.

The added surface area of the nut (nut minus bolt)  calculates out to about 1.16" sq., that doesn't seem all that substantial. A 2"x2" 1/2" thick plate welded to the existing nut would almost quadruple that. I think that will be my plan.

-Mike-
WA6ZTY




>________________________________
> From: Matt <km5vi at flukey.cc>
>To: 'reflector -tower' <towertalk at contesting.com> 
>Sent: Saturday, November 2, 2013 11:13 PM
>Subject: [TowerTalk] FW:  Base Anchor Bolts
> 
>
>The link below shows some diagrams of different anchor bolt types.  Which
>ones do you have?   The last HDX572 design calculations I have from UST
>specify (6) 1" by 27" ASTM F1554, grade 55 (55,000 psi yield), with type E
>block arrangement using a 2" square x 5/8" thick A-36 (36,000 psi yield)
>steel block welded to the top die of the nut.   Min embedment was 21".  This
>arrangement with a 5.5' x 5.5' x 7.5' footing was rated at 55,000 ft lbs
>overturning moment in 100 psf soil.
>
>http://stanley-sales.com/media/e5b0d8a7677e8f11ffff89b7ffffe904.jpg
>
>I know that the ASCE revised the their standards a few years back resulting
>in more conservative designs for anchor bolt pull-out strength.   We
>routinely run computer analysis for anchor pull-out these days considering
>not only the embedment but also the overall geometry of the footing,  The
>last two shipments of grade 55  anchor bolts I purchased from my anchor
>supplier were fabricated to the new ASTM F1554  standard and were Type F
>with the heavy square block sandwiched between two welded nuts.   FYI -
>bolts I received from UST under the old design standards were ASTM A36
>(36,000 psi) with Type D washer & nut welded to the base. 
>
>I have never heard of an anchor bolt pull-put failure on a UST.   I would be
>curious if anyone on the reflector has?
>
>Hope this helps,
>
>Matt
>KM5VI
>
>-----Original Message-----
>From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Mike
>Fahmie
>Sent: Saturday, November 02, 2013 8:49 AM
>To: towertalk at contesting.com
>Subject: [TowerTalk] Base Anchor Bolts
>
>My HDX-572MDPL came with 1" anchor bolts with a welded nut at the bottom. 
>The nut diameter is only slightly larger than the shaft so I am considering
>the addition of a heavy washer wired against the nut to increase the
>'grab'.  Is this a good idea?
>
>How does the welded nut approach compare with 'L' shaped anchor rods?
>
>-Mike-
>WA6ZTY
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