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RE: Concentrated Load at Edge of Pedestal

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Mohr’s what?  I haven’t heard that term used since I was in college. J

 

Joseph R. Grill, P.E. (Structural)

Shephard - Wesnitzer, Inc.

Civil Engineering and Surveying

 

-----Original Message-----
From: Nels Roselund [mailto:njineer(--nospam--at)att.net]
Sent: Wednesday, July 19, 2006 2:49 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Concentrated Load at Edge of Pedestal

 

Mike,

 

How about doing an analysis using Mohr’s Circle, and the Section 11.3 of ACI 318 [2006], equation. 11-4.  Look for a plane for which the shear component exceeds the concrete shear capacity, taking into account the effects of the normal component acting on the same plane to increase the shear capacity.  If there is such a plane, you would add horizontal stirrups crossing the plane.  I don’t know how to determine the effective width measured parallel to the edge that you are concerned about, but perhaps the full length of the edge could be considered effective – For the dimensions you’ve cited, it doesn’t seem like a chunk of concrete of length less than the length of the edge would pop out under the load.

 

Nels Roselund, SE

South San Gabriel, CA

njineer(--nospam--at)att.net


From: Ganesh Thiagarajan [mailto:cethia(--nospam--at)gmail.com]
Sent: Wednesday, July 19, 2006 3:31 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Concentrated Load at Edge of Pedestal

 

Brackets and corbels are typically desinged for shear friction and moments due to eccentricity of the loading. However, in the pedestal these actions for the loading described may not occur (at least the shear friction part).

 

Maybe you could also consider full loading on one column and some minimal load on the other in order

to get a higher moment value from which you can calculate the strains, bearing etc.

 

Ganesh

 

On 7/17/06, Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu> wrote:

While it may or may not address your specific question, section 11.9 in
ACI 318 does deal with "special provisions for brakets and corbels".  I
would take a look at that section if you have not done so already.

Regards,

Scott
Adrian, MI


On Mon, 17 Jul 2006, Mike Zaitz wrote:

> I have a condition where I will have concentrated loads near the edge of the
> concrete pedestal under some latticed columns.  The pedestal is 4'-0" x
> 2'-0" with 2-W14x43 columns with the webs parallel to the short dimension.
> The centerlines (parallel to the web) are only 5 inches from the edge.  For
> this case my factored load is only 157 kips but on other areas they will be
> higher.  I have checked the bearing for the concrete and am trying to find
> anything for verifying that I will not spall the edge of the pedestal.  I do
> not find anything in the code (ACI 318-99) that addresses this condition
> (other than the concrete bearing).  Is there something I am missing?
>

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