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RE: Anchor Bolts in Fatigue

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Use the F 1554 and reference ASCE "Design of Anchor Bolts in Petromhemicai Facilities". I would be inclined to go with the 55 ksi anchor rod and galvanized steel. This document contains the rules for anchor rod pretensioning.

If galvanizing can't be done, go to the ASTM A 193 series in SS, but work with a metalurgist to avoid galling issues. With stainless steel, I like to use Neverseeze.

Regards,
Harold Sprague





From: "Deke Black" <deke.black(--nospam--at)nishkiandean.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: Anchor Bolts in Fatigue
Date: Tue, 28 Aug 2007 11:57:45 -0700

I have a few questions about specifying anchor bolts that will be
subjected to fatigue loads.  Hopefully somebody has some experience and
can help me.



My first question, I was going to specify A449 threaded rod because I
know A449's properties are similar to A325, or Grade 8 bolts, which are
commonly used for fatigue (and have limiting stresses based on the
number of cycles).  Is anyone aware of limiting stresses for fatigue
loads of either F1554 Gr.105 or A354 Gr. BD?



Secondly, there is going to be a pretension in the bolt (I believe 125%
of the fatigue loading).  The manufacturer of the equipment is calling
for there not to be a bond between the anchor bolt and the concrete in
the top 7" of embedment (from the underside of the base plate down).  It
was my understanding that you should not have the bond for the full
length of the anchor bolt, and to develop the pretension in the head (or
bearing plate) at the bottom of the anchor bolt.  It seems that you
would have a problem keeping the pretension over time if the lower
portion of the bolt bonds to the concrete.  Also, what is the best way
to keep the concrete and the shaft of the anchor bolt from bonding?
I've read to grease the bolt, but I've also heard not to.  I also heard
of using a bond breaker (the same as used for forms) and of putting on
electrical tape around the bolt.  Are any of those the "best" method, or
are there any that are better?



Last, I need a method of corrosion protection.  I don't want to hot dip
galvanize because the bolts are high-strength and are subject to
fatigue.  Would the best method be a paint that contains zinc - and if
so, can anyone point me in the right direction for the specification of
such a paint?



Thanks for your help!



Deke Black

deke.black(--nospam--at)nishkiandean.com


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