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RE: Reinforcing for Anchor Bolt Breakout

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Thanks for the info.   I don't believe a hairpin in applicable here.  Concrete breakout is the tension shear cone pullout.  The ACI specifically states hairpins are good for shear reinforcing but they don't give any suggestions for tension breakout.  I don't see how a hairpin would help the breakout failure.  I was considering thickening the footing at the anchor bolts, extending the anchor bolts down below the bottom mat of footing reinforcing and using the concept of shear friction reinforcing from the bottom mat reinforcing to intercept the failure cone.  I would like to see some printed literature stating this works first though.  I have heavily loaded anchor bolts in tension.
 
Rich
 
 
 
 
 
 The "PIP STE05121 Anchor Bolt Design Guide" uses hairpins or additional straight rebar next to the anchor bolts to do this.  PIP stands for Process Industry Practices.  The guide is based on App D 318-02.


From: Haan, Scott M POA [mailto:Scott.M.Haan(--nospam--at)poa02.usace.army.mil]
Sent: Wednesday, April 19, 2006 6:15 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Reinforcing for Anchor Bolt Breakout

I thought ACI appendix D is meant for unreinforced concrete.  It seems logical that if the concrete has to pop out past horizontal reinforcement that the shear friction the horizontal reinforcement produces could be used to resist the pop out and that if the pop-out happens adjacent to vertical reinforcement that you could count on the strength of the steel developed above and below the pop-out to resist the pop-out. 
 
I have not seen this is a design guide but I have seen engineers do it.


From: Rich Lewis [mailto:seaint03(--nospam--at)lewisengineering.com]
Sent: Wednesday, April 19, 2006 12:46 PM
To: seaint(--nospam--at)seaint.org
Subject: Reinforcing for Anchor Bolt Breakout

Are there any practical ways to reinforce a footing for concrete breakout of anchor bolts as defined in ACI appendix D, section 5.2?  If Break Out is the controlling factor in the design of the anchor, and I don’t want to design the footing thickness based on anchor bolts, what would be a reinforcing configuration to strengthen the breakout capacity?

 

Thanks for any insight.

 

Rich