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RE: Anchor Bolts embedded in Reinforced Concrete

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See the July issue of Structure Magazine (www.structuremag.org), 'From
Experience' section, for a discussion of one office's practices,
seemingly along the lines of what you describe.  It makes sense to me
when feasible.

Eric

-----Original Message-----
From: Kestner, James W. [mailto:jkestner(--nospam--at)somervilleinc.com] 
Sent: Friday, July 30, 2004 1:14 PM
To: SEAINT
Subject: Anchor Bolts embedded in Reinforced Concrete

I have recently waded thru all the formulae in ACI 318-2002 Appendix D
for computing anchor bolt capacities! IBC 2000 Section 1913 is similar.
Wow!

It seems all the formulae are based upon capacities of unreinforced
concrete. 

When anchor bolts, subjected to shear, are embedded in a reinforced
concrete pier, it would seem that the ties will work like stirrups to
resist the shear if they are spaced at d/2. For some pier sizes, the d/2
requirement is a tighter tie spacing than normally required for piers.
The compressive force in the pier (if there is any) will obviously
increase the shear capacity. To prove that the anchor bolts are OK in
shear, it seems logical to check the allowable shear of the reinforced
pier instead of the breakout strength of the anchors in the unreinforced
concrete. Steel strength and pryout strength of the anchors also need to
be checked.

When anchor bolts, subjected to tension, are embedded in a reinforced
concrete pier, it would seem that the overlap of the anchor bolts and
the reinforcing steel has to be long enough to transfer the tensile
forces. To prove that the anchor bolts are OK in tension, it seems
logical to check the tension that can be transfered to the reinforcing
instead of the breakout strength of the anchors in the unreinforced
concrete. Of course, the steel strength of the anchors also need to be
checked.

I would then use the minimum values of the capcities in the combined
stress equations. 

For anchors in footings, I use the formulae in the code for anchors in
unreinforced concrete. 

Is this how others are currently doing it or are you relying on old
tables like I used to? You need a major spreadsheet to handle these new
calculations. Pretty involved process!

Any comments?


> Jim K.

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