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RE: Threaded ASTM A706 Rebars for Anchor Bolts

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Suresh,
Dayton has a good product line, but requires a bit of caution.  If you are using a threaded bar, and you need a given size bar for strength, you need to select the next larger bar because of the reduction in the threaded area.  The only threaded coupler that can give full strength is the tapered coupler that is used by Lenton.
 
Szuchuan,
When you say "easier" to develop the embedment strength, I am curious about easier for whom.  It is probably easier for the designer, but not for the field. 
 
Rebar is generally installed by a different iron worker crew as opposed to the antenna.  No matter what you show on drawings, rebar is installed to a much more generous tolerance (ACI 117 Section 2.3).  Anchorages and anchor bolts should be installed to the tolerance indicated in AISC 303, Section 7.5.  Further, if the placement is critical, a gage metal template should be required.  The difference in tolerance is huge when you compare ACI and AISC.  A gage metal template will be fabricated within 1/16" tolerance.
 
I would then suggest that an ASTM F 1554 anchor rod be used with locked nut forming the head.  You can specify a 105 ksi material.  When or if you have to calculate (and prove) the deflection of the antenna, the rebar anchorage will not perform as a rigid anchor.  The strain varies as you develop the rebar with depth and there will be local slippage which will effect the elongation of the anchorage and thus effect the deflection.  If you use a headed anchor, you can preload the anchor and achieve a reliable and consist ant strain and a reliable deflection calculation. 
 
You can lap rebar into the development cone of the anchor rod to assure that you can transfer the applied stresses into the concrete. 

Regards,
Harold Sprague

> From: Suresh.Acharya(--nospam--at)ci.concord.ca.us
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Threaded ASTM A706 Rebars for Anchor Bolts
> Date: Thu, 24 Jul 2008 14:46:15 -0700
>
> See
> http://www.daytonsuperior.com for rated splicing
> system/couplers/pre-threaded bars.
>
>
> -----Original Message-----
> From: Szuchuan Chang [mailto:szuchuan(--nospam--at)gmail.com]
> Sent: Thursday, July 24, 2008 1:50 PM
> To: SEAOC
> Subject: Threaded ASTM A706 Rebars for Anchor Bolts
>
> List,
>
> Need to develop 1.25" diameter anchors for the base of an antenna dish to
> the concrete pedestal.
>
> If I leave the #10 (ASTM A706) out of concrete as dowels, will the
> contractor have problem to thread the rebar for bolting it to the base?
>
> It is much easier to develop the embedment strength on rebars with
> deformation than the ACI Appendix D with anchor bolts.
>
> Thanks
>
> Szuchuan Chang
>
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