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Fw: Avo wrt ACI 318 Appendix D

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----- Original Message -----
From: catchall
Sent: Monday, October 20, 2003 12:07 PM
Subject: RE: Avo wrt ACI 318 Appendix D

Jack, sorry to reply to you directly. My email address registered with seaint has been down. Please copy this to the list so that the other members can respond to anything I've told you.
Theoretically Avo approaches infinity as C1 approaches infinity.  This is not very helpful since equation D-21 approaches zero as Avo approaches infinity.  The equations allow you to calculate a smaller, finite, and more useful value for Avo.  This value is independant of C2 or any other edge distance.  If there are any edge effects they should appear in the calculation of Av not Avo.  This approach should be conservative since it causes the ratio Av/Avo to be smaller.  Av is limited by the edge effects (side1, side2, side3, bottom) and Avo is not.
On the other hand, if I were not satisfied that the figures RD6.2.1(b) for Av correctly represent the actual projected area of the failure surface for my particular situation than I should calculate Av myself using integral calculus or grains of rice or whatever.
I hope I haven't missed your point. Let me know.
I see how this could be considered overly conservative.  There is probably a way to further reduce Avo so that it is even smaller than permitted in D-22. Say for example when the slab depth is insufficient to allow Av to ever reach the theoretical Avo.
btw, I'm sure you are just using these numbers as illustrative examples, but I'm having a hard time visualizing a 20' edge distance being relevant in a 2" or smaller bolt. The bolt shear failure mode would most certainly govern.   
15                               Message:0015                           15
From: "Shapton & Partners" <
To: <
Subject: Avo wrt ACI 318 Appendix D

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I have asked this question before.  One time I think I sent it =
incorrectly or to the wrong place.  Another time the server went down - =
I hope this question was not the cause.  If somebody would take the time =
to set me straight on this I would really appreciate it.

Equation D-22 sets Avo as a function of C1.  Avo is also defined wrt an =
anchor remote from edges ( C1 approaches infinity).  Figure RD.6.2.1 =
(plan view) appears to require C2 to be equal to 1.5 x C1to eliminate =
the parallel edge influence on Avo.  The way I am reading this is that =
the C1 dimension for an isolated anchor would always be h/1.5 per =
Example: C1 =3D20 feet, C2 =3D 20 feet.  C1 and C2 are both large but as =
C2 is not equal to 1.5xC1 or 30 feet, the full breakout cone , in  plan =
view, cannot be developed.  Also if the depth of the slab is not 30 =
feet, the slab bottom becomes the third influencing edge and D.6.2.4 or =
h/1.5 controls.

Except for this Avo business Appendix D appears pretty similar to Shipp =
and Hanginger (AISC 2nd qtr., 1983).

Thanks for any help, Jack Shapton

Christopher A. Banbury, PE
Vice President
Nicholson Engineering Associates, Inc.
PO Box 12230, Brooksville, FL 34603
7468 Horse Lake RD, Brooksville, FL 34601
(352) 799-0170 (o)         (352) 754-9167 (f)