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RE: steel formdeck as shearwall?

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One thing I'd like to add that I haven't mentioned is that seismic is what got this question going in the first place.  I hated the idea of the straps on studs for seismic reasons.  This is what generated a question for a different solution.  I feel like I'm making it look like my head is in the sand.  It's not.

There a place in NW Alabama that I go backpacking.  It's a canyon with 100' bluffs on both sides of the river.  There are all of these house sized boulders laying in the bottom of the canyon and the river.  I've taken folks up there a good bit and they always ask where the boulders come from.  I point up to the bluff line and you can always find the location it fell from.  My answer is always, "New Madrid, 1811"

John C. Jones, PE
Barnett Associates
Pell City, AL
205-884-5334
205-884-0099 (fax)


-----Original Message-----
From: Sprague, Harold O. [mailto:spragueho(--nospam--at)bv.com]
Sent: Friday, October 31, 2003 9:40 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: steel formdeck as shearwall?


You really should read the book "The New Madrid Earthquakes" by Penick, and
the research by Nuttli and Hopper.  This was the beginning of the work by
Algermissen, and later by Frankel and Leyendecker on the New Madrid Seismic
Zone (NMSZ).  There were 3 earthquakes between 1811 and 1812 that were
larger than the 1906 San Francisco earthquake, and covered significantly
more area.  There were also over 1800 additional earthquakes during that
time period.  It was only a fluke of geologic time versus the development of
civilization that there was no greater damage and loss of life.  

The seismicity of Birmingham is just as real as it is in Memphis.  The
seismicity has the same point of origin which is the NMSZ.  The major point
is that the effected area of an inter-plate fault is over 10 times greater
than the fault structure of the tectonic boundaries as exists on the West
Coast.  

The key lesson of seismic performance is in the detailing, and that is what
is triggered by the seismic design categories.  

Prudent engineering should not have to be dictated by law.  It should be
dictated by the state of the practice.  By law, Memphis was a self declared
seismic free zone until 1997 when the State of Tennessee forced Memphis to
design for seismic.  When (not if) the big one hits, those same legislators
will wonder how this disaster could have happened, and lament that it was an
unforeseen act of God.  I see it as negligence.  

Regards,
Harold O. Sprague

-----Original Message-----
From: John C. Jones [mailto:john(--nospam--at)struct-engr.com] 
Sent: Friday, October 31, 2003 6:27 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: steel formdeck as shearwall?

Thanks Ed, I think you're the definitive swing vote to make sure I get CMU
for shearwalls.

Thanks for the seismic input.  I realize it can control, and a month from
now, when the project is in my hands, it'll be checked as always for these
conditions.  

IBC makes a roughly 4x change in seismic forces in the Birmingham area.  It
would definitely control if that was what I was using.  SBC, maybe/mabye
not.  The recurrence interval is now about 2500 years under IBC.  I'm not
using that unless dictated by law.  If I was around Memphis or Charleston,
heck yeah, I'll get into it.

John C. Jones, PE
Barnett Associates
Pell City, AL
205-884-5334
205-884-0099 (fax)


-----Original Message-----
From: Ed Tornberg [mailto:edt(--nospam--at)blazerind.com]
Sent: Thursday, October 30, 2003 5:46 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: steel formdeck as shearwall?


John,
We had to look into this on a few projects where it had to be
non-combustible and lightweight.  The options for steel stud walls came
out as:
 
1.  Hardy frames
2.  Light gauge "diaphragm" material, similar to form deck.
3.  Strap bracing
 
The hardy frames were excellent on a single story project where we
designed the holdown bolts to attach to structural steel channel serving
as a floor rim.  
 
The problem with steel siding is that the manufacturers really don't
understand what documentation we need to apply it as "sheathing"  They
sometimes could come up with an ICBO listing for roof diaphragms, but
not for walls.  In our case we were looking for something with a very
low profile - not B-36 or other heavy stuff.  We came close with some
material but the price for a small job was astronomical, and we nixed
it.  If you really want some leads on manufacturers contact me and I'll
try to dig up the notes.
 
Thus we ended up strap bracing on a couple of projects, which works but
oh what a pain to do the calcs when you're used to specifying sheathing.
You might as well have the fee figured the same as for doing CBFs, but
with many more braces, since they're relatively wimpy.  And they do
bulge out the walls, especially if you're using gussets at the brace
corners, which we had to do to make the connections work.
 

Ed Tornberg, PE 
Blazer Industries, Inc. 

Aumsville, OR
503-749-1900 

 

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