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Concrete Pryout Strength of anchors in Shear 2

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tonycampos88

tonycampos88

Structural
Aug 22, 2013
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Hello,

I'm designing the anchors from a pre-manufactured metal building that is going to be supported on 27x27 columns. I'm having problems with the concrete pryout strength in shear. According to what I understand from the code, Anchor reinforcement would only help concrete breakout, but not pryout. Is there anything (more reinforcement) that we can do to avoid this failure without changing my column dimensions?
Thanks
 
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I have only seen some people reference that as long as the anchor is a certain length, pryout should not control. No specific code reference that I know of.
 
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Ah yes, the famous Metal Building Anchorage issue. A while back I had a similar problem. I lengthened the bolts such that they were embedded deep into the footing (they ended up about 4'-0" long) and used the edge distances to the footing rather than the column (I did the calculations for pryout just for the portion embedded in the footing) to get them to work. This only works if the columns sit on spread footings.
I always felt that I was gaming the system, but I had to do something to make the numbers come out.
 
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According to the ACI- appendix D the pray-out equation is a factor multiplied by the tensile breakout strength. tension breakout strength depends mainly on the embedded length and the edge distance. So, think about playing these two variables or using a shear key which might be more effective in transferring shear
 
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Just so that you guys now, I e-mailed the ACI technical guys and they said Pryout will not control if embedment depth is greater than 5d, but that the code hasn't been changed!
 
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27x27 concrete columns with steel building base plates mounted on top?

If so, I would use all-thread rods and lap them with vertical column reinforcement in the column to get full development, and avoid APP D all together.
 
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Hi,

You need to use supplement reinceforcement... When you use it you dont need to worry about pryout or breakout in shear, because the anchor bolt and rebar lap each other (need longer anchor) and work as one, so pryout or breakout dont happen.

Review PIP STE05121 Anchor Bolt Design Guide, you will find there how design this supplement reinceforcement.

Regards
 
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