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RE: ACI 318-02 Appendix D

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Bruce:

The code reviewer is likely talking about "Condition A" vs. "Condition B"
for the phi factor in section D.4.4.  If supplemental reinforcement that
will "cross" the potential concrete failure surface (Condition A) then you
get to use a large phi factor.  What Appendix D does not really discuss is
_HOW_ to design that supplemental reinforcement (i.e. how much and what
size).  Section D.4.2.1 kind of deals with this, if you look at the
commentary.

HTH,

Scott
Adrian, MI


On Mon, 22 Nov 2004, Bruce Holcomb wrote:

> I spoke to the code reviewer who is reviewing my project and he said that App D does account for the use of vertical rebar in a pedestal by giving a different reduction factor for design than for the case of unreinforced concrete.  I have been looking for this and can't find it... can you give me any help?  He couldn't give me a reference because he doesn't have a copy of the ACI code at his office.  Basically, he doesn't agree that you need to use another design method to consider the effects of the vertical rebar.  If I have to re-design as plain concrete, my pedestal will get a lot bigger and the anchor bolts will probably need to be longer too.  I don't have a problem with using App D, but I don't want to penalize my design because I use it.
>
>
>
>
>
> Bruce D. Holcomb, P.E., S.E.
>
> Structural Engineer
>
> Butler, Rosenbury & Partners
>
> 300 S. Jefferson, Suite 505
>
> Springfield, MO 65806
>
> ph. 417-865-6100
>
> fax 417-865-6102
>
> www.brpae.com
>
> Architecture, Engineering, Interior Design, Planning & Development
>
> Your Vision.  Our Focus.
>
>
>
> -----Original Message-----
> From: Hood, Matthew O. [mailto:HoodMO(--nospam--at)ci.anchorage.ak.us]
> Sent: Friday, November 19, 2004 5:15 PM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: ACI 318-02 Appendix D
>
>
>
> Bruce,
>
>
>
> Section D.4.2.1 says that "The effect of supplementary reinforcement provided to confine or restrain the concrete breakout, or both, shall be permitted to be included in the failure models." If you then read the commentary it says you can use reinforcement oriented in the direction of load and fully anchored on either side of the failure cone to transfer the required forces. I take this to mean that you draw the failure plane from your anchor bolt and then make sure your rebar can be developed on either side of this plane. If that's the case, then the concrete won't break out and the load will be transferred to the reinforcement.
>
>
>
> HTH,
>
> -Matt
>
>
>
>
>
>
>
> Matthew O. Hood, E.I.T.
> Plan Review Engineer
> Municipality of Anchorage
> 907-343-8451
>
> -----Original Message-----
> From: Bruce Holcomb [mailto:bholcomb(--nospam--at)brpae.com]
> Sent: Friday, November 19, 2004 1:52 PM
> To: seaint(--nospam--at)seaint.org
> Subject: ACI 318-02 Appendix D
>
>
>
> I have been asked to verify an anchor bolt design based on IBC 2003 which has either the ASD table in section 1912 or the strength design approach of section 1913 which basically just references ACI 318-02 Appendix D.  I typically design anchor bolts and base plates in accordance with AISC Design Guides 1 & 7, so I need to get up to speed quickly on Appendix D of ACI 318-02.
>
> My main question is, how does Appendix D account for the vertical reinforcing in a concrete pedestal?
>
> Long story short... I have a reinforced concrete pedestal on an individual column footing for a fixed-base column.  My anchor bolts are 1" diameter by 30" embedment, which puts the nut at the bottom of the anchor bolt below the bottom of the pedestal and in the footing.  I can draw failure planes and explain that I am using the tensile strength of the rebar to transfer the load into the footing, but I am being asked by a plan reviewer to verify by Appendix D.
>
> I remember reading somewhere that 12*AB diameter embedment in 3000 psi concrete provides strength = anchor bolt yield.  Of course, this is for the case where the anchor bolt is not near an edge of concrete.  I think this was in an AISC publication... can anybody help me find this?
>
>
>
> Bruce D. Holcomb, P.E., S.E.
>
> Structural Engineer
>
> Butler, Rosenbury & Partners
>
> 300 S. Jefferson, Suite 505
>
> Springfield, MO 65806
>
> ph. 417-865-6100
>
> fax 417-865-6102
>
> www.brpae.com
>
> Architecture, Engineering, Interior Design, Planning & Development
>
> Your Vision.  Our Focus.
>

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