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RE: holdowns @ stucco walls

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This is a good question. My initial opinion would be to disregard the shear
material and consider only the applied load on the panel. If there is
sufficient uplift, then install the holddown.
In URM design this would be considered the difference between capacity and
demand. The demand is from the diaphragm and is what is calculated by the
original engineer. The capcity is the value of the wall sheathing which has
been reduced from the original 180 plf for stucco down to (I believe) 90 plf
in the city of Los Angeles.
Assuming the connection of lath and stucco to studs is strong, then the
capacity may be closer to the code rated values. In either case, I believe I
would supply the holddown if the demand is applied and an uplift greater
than 300 or 500 lbs is calculated. Some engineers feel that the connection
of the anchorbolts to the foundation and the connection of the sheathing is
good for at least 3-500 pounds of uplift and will refrain from providing
holddowns unless greater than this.

Dennis Wish PE

|-----Original Message-----
|From: Mark and Jessica Pemberton [mailto:jmpember(--nospam--at)softcom.net]
|Sent: Tuesday, February 24, 1998 7:29 PM
|To: seaoc(--nospam--at)seaoc.org
|Subject: holdowns @ stucco walls
|
|
|This may be a silly question but here it goes... is it acceptable
|to call out bolt type holdowns at stucco or gypsum board
|panels used as shear wall?  I was originally instructed to never
|do this, but have come across plans by others that use this
|combination frequently.  Typically if a wall requires a holdown
|stucco or gyp don't calc out for shear, but there are times that
|the dead load is light and holdowns are required with low
|unit shear.  Presently, if a shear wall requires a holdown we
|will specify plywood regardless.  Is this necessarily reducing
|the "value-engineering" of the project, or is there a good reason
|to stick with plywood in these situations?
|
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