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RE: Anchor Bolts embedded in Reinforced Concrete

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There is some discussion in the NCSEA/CASE/SEI Structure Magaine of July
2004.

craig


-----Original Message-----
From: Kestner, James W. [mailto:jkestner(--nospam--at)somervilleinc.com] 
Sent: Friday, July 30, 2004 2:14 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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