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RE: Multi-story wood framed w/lots of openings

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Even though I wouldn’t use a perforated shear wall (w/o shear transfer around openings), it’s probably conservative to use this method to calculated the deflection of the assembly. There is an example in “Diaphragms and Shear Walls”, published by the American Plywood Association (http://www.apawood.org/pdfs/download_pdf.cfm?PDFFilename=managed/L350.pdf) which shows the familiar four term deflection equation modified by dividing the entire result by the Shear Capacity Adjustment Factor (SCAF). To me, it seems that it would be more appropriate to modify just the shear term (vh/Gt) by 1/SCAF. That’s why it seems conservative to modify all four terms by this factor. Still, the results should be satisfying since the other three terms should have much less contribution to the deflection of the shear wall system than individual piers just due to the improved geometry.

 

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: Michel Blangy [mailto:mblangy(--nospam--at)satco-inc.com]
Sent: Thursday, March 10, 2005 12:09 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Multi-story wood framed w/lots of openings

 

How might one calc. deflections on this type of arrangement?

-----Original Message-----
From: Bill Allen, S.E. [mailto:T.W.Allen(--nospam--at)cox.net]
Sent: Thursday, March 10, 2005 10:56 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Multi-story wood framed w/lots of openings

I guess this is one (of the few) times I agree with Dennis. If I’m going to use a shear wall with openings, I’m going to strap across the openings using the methodology presented in the Seismic Design Manual (Volume II, starting on page 40) published by the Structural Engineers Association of California. Often, I have cases where I physically cannot transfer the load around the opening. When that happens, I use two piers or some other solution. Perhaps APA (or someone else) can do some cyclic testing on a perforated shear wall assembly and ask SEAOC to review and comment.

 

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: Rhkratzse(--nospam--at)aol.com [mailto:Rhkratzse(--nospam--at)aol.com]
Sent: Thursday, March 10, 2005 10:36 AM
To: rgarner(--nospam--at)moffattnichol.com; seaint(--nospam--at)seaint.org
Subject: Re: Multi-story wood framed w/lots of openings

 

In a message dated 3/10/05 10:29:04 AM, rgarner(--nospam--at)moffattnichol.com writes:

I just looked at the AF&PA perforated shearwall document.  The top detail of Figure 5 on page 8 relies on nails in withdrawal to resist uplift.  I don’t agree with this.  Anyone else?  It would be easy enough to strap this joint, however, as shown in the other connection in this detail.


I have similar concerns.  I recommend watching Simpson Co.'s video of a dynamic test of a plywood shear wall, with the end studs bouncing about an inch off the bottom plate as the forces reverse, tearing the plywood away from the framing near the bottom of the end stud, etc.  Essentially the 'quake disassembles the wall.  It put the fear of (earthquake) into me!

Ralph
Ralph Hueston Kratz
Structural Engineer
Rhkratzse(--nospam--at)aol.com

510-236-6668
Fax 510-215-2430

724 McLaughlin Street
Richmond CA 94805-1402 USA