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RE: Tilt-up connections (UNCLASSIFIED)

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Classification:  UNCLASSIFIED 
Caveats: NONE

ACI 318 16.5.1.3 says the same thing.  "No tension at the base"  would mean
the resultant gravity load acted in the middle third of the panel length
otherwise there would be tension between the wall and the footing and the
panel would still need to have the minimum connection. 

If ACI 318 chapter 21 says that precast walls and connections need to meet
special requirements in seismic design category D, then Jake's competition
still has to do those unless he's writing his own code.  I don't see where
ACI 318 says chapter 21 precast requirements don't apply to tilt-up.

-----Original Message-----
From: Mark E. Deardorff [mailto:mdeardorff(--nospam--at)burkett-wong.com] 
Sent: Thursday, January 04, 2007 2:05 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Tilt-up connections (UNCLASSIFIED)

UBC 1916.5.1.3 says that the anchorage only needs to be to the slab if no
uplift is present.

Mark E. Deardorff
Structural Engineer

3434 4th Ave
San Diego, CA 92103
P 619.299.5550 x348
F 619.299.9934
mdeardorff(--nospam--at)burkett-wong.com
 

> -----Original Message-----
> From: Haan, Scott M POA [mailto:Scott.M.Haan(--nospam--at)poa02.usace.army.mil]
> Sent: Thursday, January 04, 2007 2:48 PM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Tilt-up connections (UNCLASSIFIED)
> 
> Classification:  UNCLASSIFIED
> Caveats: NONE
> 
> I have one of those Tilt-up Construction Association manuals that I 
> loaned to a friend so I don't have it in front of me right now but I 
> think it shows the wall anchored to a slab closure strip and not 
> connected to the foundation.
> 
> Just being devil's advocate here, but for a one story building if 
> there is no uplift and assuming that the shear can be taken out in the 
> slab on grade with a closure strip, why force a minimum positive 
> connection to the footing?
> 
> I could see having a minimum connection for a multistory precast 
> building where the connection to the footing transmits shear or 
> overturning or you are
> doing a blast design.    
> 
> -----Original Message-----
> From: Jake Watson [mailto:jake.watson1(--nospam--at)gmail.com]
> Sent: Wednesday, January 03, 2007 10:41 AM
> To: SEAINT
> Subject: Tilt-up connections
> 
> List,
>     ACI-318 05 has revised the precast seismic connection 
> requirements.  The new concepts on the surface appear to be well 
> considered.  However, some local firms have taken an interesting twist 
> on them.  I generally anchor tilt panels to the footing for a 10 kip 
> minimum per the precast chapter, regardless of the demand.  Now under 
> the new provisions we will also make that connection meet the new 
> ductility provisions in chapter 21.  We were doing this before with a 
> slightly different philosophy, but it appears to get very close to the 
> same results.
> 
>     A competing local engineer pointed out that the PCA Notes to 318 
> 05 state the ductility provisions and minimum connections don't apply 
> to tilts.  SEAOC and some letters to Stuctures Magazine feel anchoring 
> to the slab only is a bad idea in high seismic zones (say seismic 
> design category C+).
> Some local firms will do an overturning calculation with an R of 5, 
> determine there is no net uplift, and only anchor to the slab.  How 
> does PCA justify that statement and is there any rational reason in 
> ACI 318 to support it?
> 
> Jake Watson, P.E.
> Salt Lake City, UT
> 
> Classification:  UNCLASSIFIED
> Caveats: NONE
> 
> 
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Classification:  UNCLASSIFIED 
Caveats: NONE


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