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RE: shear friction from horizontal top reinforcement, to resist holdown anchor pop out in A footing?

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I’d like to see your PDF.  I don’t know if I can be of any assistance, but I have considered the top steel in resisting anchor rod pullout.  I don’t have a complete answer, or even a good partial answer, but if you have a plain concrete footing and a footing with top steel, it seems pretty obvious that the footing with top steel with have greater pullout resistance.  I’ve considered shear friction and simply the rebar steel shear strength (0.4*Fy).  I think there is a factor to account for the rebar in the ACI design method, but I don’t recall right now.

 

 

BDH

 


From: Haan, Scott M POA [mailto:Scott.M.Haan(--nospam--at)poa02.usace.army.mil]
Sent: Tuesday, October 03, 2006 4:28 PM
To: seaint(--nospam--at)seaint.org
Subject: shear friction from horizontal top reinforcement, to resist holdown anchor pop out in A footing?

 

Can you use horizontal reinforcement in the top of a footing to resist the pop out of a concrete tiedown anchor rod?  I  talked about this idea  with an intelligent engineer and he said it can't be done. 

 

I drew a free body diagram of a pop out cone with the reinforcement developed in the cone and with the shear friction parallel to the cracks with the vertical of shear friction component cancelling out the upward force and the horizontal component cancelling out.  I'll e-mail a .pdf of the solution if someone wants to look at it and tell me where it goes South.

 

He said the tension is acting vertically across the inclined crack failure plane, and you've got the shear component parallel to the crack and tension component perpendicular to the crack, and that the shear friction  formula in ACI 318 for reinforcement at an angle to the crack only applies to force component parallel to the crack. 


This is where my head starts hurting assuming the free body diagram is inappropriate, couldn't you still increase the amount of horizontal reinforcement across the crack to cancel the horizontal component of tension perpendicular to the crack and add more shear friction for the component parallel to the crack ect...etc.... 

 

I don't believe horizontal reinforcement couldn't clamp concrete from popping out with enough horizontal reinforcement clamping the pieces together.