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RE: Tilt-up connections (UNCLASSIFIED)

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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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