Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Detail Review

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Overall I like the detail, with some modifications.  

First, this looks like a shear wall; is that a piece of plywood under the
gyp on the left side?  The only way to really verify proper nailing (other
than full-time inspections) would be to specify steel angles (Simpson A23 or
L30) between the PSL and the top plate, but watch nail edge distances on the
PSL.

Second, I have concerns with the PSL.  PSL?s don?t come in 8.5?.  The widest
?column? is 7? and the shallowest ?beam? is 9.25?.  This means field ripping
(probably rip a 16? beam in half), and the resulting inconsistencies.
Although, I calculate the wall to be 6.5? (with 1/2? plywood), so a 7? would
give 1/4? overhang on each side.

Others have mentioned the cross-grain bending; that and shear are a serious
concern.  I have an end cut off a PSL sitting on the wall above my desk.  As
I'm typing this, I'm looking at it and can actually picture the grains
pulling apart in a combination of cross-grain bending and shear.  Then we'll
see your name on the next set of pictures of a collapsed apartment complex.

One idea is to use an LSL beam instead of a PSL.  You can get LSL's in 7.25"
and 8.625" depths with a width of 3.5".  Strong-axis bending is weaker than
with PSL's, but the wood grains are oriented randomly, which should result
in higher allowable cross-grain stresses.  Also, I believe they're cheaper
than PSL's.  You DEFINITELY want to call TrusJoist (1-800-628-3997); they've
always been helpful when I've had questions in the past.

Finally, to step even further outside of the box, consider going
multi-material.  Go with the 7.25" LSL and put cold-formed steel 7.25" track
(flanges down) on top of the LSL.  I know that Clark makes one in this size,
but don't know how common it is.  The system would act like a composite
beam, with the steel track in tension.  The tension anchorage would be
provided by the flanges bearing on the edges of the LSL, with nails to
prevent rotation of the flange.  Shear and hanger bearing capacity would
also be greatly improved.

Others have mentioned rotational crushing of the gypboard, but I don't see
this as a problem.  What will be a problem is the required gap between the
end of the joist and the wall, and bracing the bottom flange.  I recommend
nailing solid 2x or LSL blocking to the wall between each joist.  You'll
nail to the top plate and that lower blocking plate through the gyp, and
your joists could be out up to almost an inch and still be restrained.
Crushing of the ceiling gyp is eliminated by a small gap between the gyp and
the wall, covered by standard molding.

HTH,

---
Jason Kilgore
Leigh & O'Kane, LLC
Kansas City, Missouri
________________________________________
From: Bill Allen, S.E. [mailto:T.W.Allen(--nospam--at)cox.net] 
Sent: Thursday, August 05, 2004 4:28 PM
To: seaint(--nospam--at)seaint.org
Subject: Detail Review

Dear Colleagues;
 
My client has asked me to review a proposed detail. I have my opinions, but,
being one with an open mind, I would like to get opinions from others.
 
The detail is here:
http://www.AllenDesigns.com/projects/20401/20401_sk03.jpg
 




******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ********