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Appendix D - Breakout in Shear

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bookowski

Structural
Aug 29, 2010
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For concrete breakout in shear, anchor near edge and load towards edge, D.6.2.1 gives Avco = 4.5 x Ca1^2 and notes in the text "for a deep member". Fair enough. D.6.2.4 deals with anchors in sections of limited thickness such that "both edge distances ca2 and ha are less than 1.5ca1". What about thin members, i.e. slabs, where ha < 1.5ca1 but there is infinite edge distance for ca2? It would seem that the vertical portion of the area calc gets capped at member thickness, h. So it would be Avco = (2 x 1.5ca1) x h.

Although it doesn't state the above anywhere it seems to make sense and goes along with the diagrams/derivations. However when I run this in Hilti Profis I see that they're using the ca1^2 and therefore getting a huge area. Maybe a mistake in profis - or am I missing something?

ACI does address this exact configuration for the group of anchors in figure .6.2.1(b) where they cap the height at "h" which would seem to confirm my way of doing it. Profis does seem to follow this diagram for the group.
 
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bookowski - are you confusing Avc with Avco? Avc is calculated based on geometry of actual condition. Fig RD.6.2.1(b) is reflecting Avc calculation. Avco is an idealized condition for a single anchor - this term will end up in the denominator of equation D-31.
 
Yeah I guess so. Avco is for anchor "unaffected by edge distance, spacing, or depth of member". What threw me was that they say the above but then there is an exception for spacing and depth in d.6.2.4 where they show modifying Avco for thin members. So it's independent of spacing and depth except when it is.
 
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