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RE: tilt-up concrete walls

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Paul –

 

There are two schools of thought here.

 

Some believe that the stretching of the chord bars (particularly if they are unbonded for some distance away from the end of the panel) between the panels negate the distribution according to stiffness approach.

 

I’m not saying which is right or which is wrong, but I know a lot of people on either side of the fence on this issue.

 

I think good judgment is required in any approach when substituting a mathematical model for reality.

 

Regards,

 

T. William (Bill) Allen, S.E. (CA #2607)

ALLEN DESIGNS

Consulting Structural Engineers

http://www.AllenDesigns.com

V (949) 248-8588

F (949) 209-2509

 

-----Original Message-----
From: Paul Feather [mailto:pfeather(--nospam--at)SE-Solutions.net]
Sent: Friday, February 04, 2005 2:32 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: tilt-up concrete walls

 

You need to distribute the shear based on relative rigidity of the wall panels.  The continuous chord reinf is also a contributing drag element for distribution of the diaphragm shear to the panels. Each panel will have a relative rigidity, and then the individual piers within each panel.

 

If the panels are "reasonably" different, there is no valid justification for assuming things will be evenly distributed. Relative rigidity distribution will be more accurate and proper.  For the even distribution idea to be valid, each panel would have to be able to deflect independently along the diaphragm length with local deformation of the diaphragm and the chord. 

 

Paul

----- Original Message -----

Sent: Friday, February 04, 2005 11:25 AM

Subject: tilt-up concrete walls

 

I have what I think would be an interesting question.

 

I have a tilt-up project that I'm working on.  So far, it's going pretty well - but I realized that I wasn't sure about distributing the in plane shears in the wall panels.  The panels are 22' tall with the roof diaphragm at roughly 19' (it varies with drainage).  At the plane of the roof diaphragm the panels are solid (no major openings) but the openings for the doors (which vary from 10' to 12') are placed such that each of the wall panels is "reasonably" different.  In other words, the openings are of differing heights and occur in different locations in each of the panels.  From the main elevation, the openings appear to be centered equally, but when you figure out where the panel joints are located, the openings are NOT in the same location for each panel. 

 

I had two thoughts.  One was that since the panels at the height of the diaphragm were solid and each virtually identical in length, the in plane shear would be distributed equally.  The other thought was that I should really think to distribute the shears based on the wall widths at the openings.

 

Obviously the first method would be (much) simpler but I wasn't sure that the second method would be much more accurate, if at all.  Any advice?

 

 

 

Thanks.

 

Chris!!

 

 

=================================
Christopher S. Campbell
O'Connor Freeman & Assoc., Inc.

916.441.5721     fax 916.441.5697

 

"They're only mad at me because I'm right"

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