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RE: Truss permanent bracing

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More interesting to me about the TPI documents is that for at least half
of the country there is no EOR or licensed designer of any sort on
residential projects.  Therefore, how can they pass responsibility on to
someone else that isn't even there?

 Patrick Clark, P.E.
Building Concepts, Inc.
1228 Pep Circle
Gardnerville, NV 89410
(775) 782-8886 x22
(775) 782-8833 fax

-----Original Message-----
From: Eric Ober [mailto:eober(--nospam--at)holbertapple.com] 
Sent: Wednesday, August 17, 2005 11:44 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Truss permanent bracing

Beyond the individual truss member permanent bracing, the bottom chord
must be considered with regard to wind uplift bracing (unless you have a
gyp board ceiling).  I put bottom chord plane bracing on the drawings.
We typically put notes on our drawings putting the truss manufacturer on
the hook for detailing the individual member permanent bracing, despite
what TPI/WTCA/IBC indicates.  We haven't had any trusses come back with
severely slender members yet, so I don't know what headaches I am asking
for yet.  

How do you build your fee to account for a situation over which you have
limited to no control?  I don't get the whole setup of waiting for the
truss manufacturer's shop drawings, which puts me on the line to get
revised drawings out ASAP as erection is proceeding shortly.  It's great
for the truss guys but garbage for us.

Eric  

-----Original Message-----
From: Neil Moore [mailto:nmoore(--nospam--at)innercite.com] 
Sent: Wednesday, August 17, 2005 12:56 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Truss permanent bracing

Actually, the truss manufacture identifies the web members that have to
be 
braced for buckling.   He should be giving you the compressive force in 
each of these web members.   You, in turn, take some rule of thumb 
percentage of that force to determine the required load to resist the 
buckling.  From there you multiply this force times the number of
trusses 
to determine a total load that somehow has to be transferred either to
the 
building or to the roof or to the gable wall.   Or you add 2x's to each
of 
the subject web members in the field to eliminate the buckling problem.

This is one of the little gotcha's that is in the TPI code.  The UBC
refers 
you to the TPI code.

I just noticed that the 2003 IBC requires in section 2304.4.1 item 17
that 
the truss shop drawings are to provide the maximum axial compressions 
forces "to design the size, connections and anchorage of the permanent 
continuous lateral bracing".   The code didn't say who was to design
this, 
but you will probably find it in the TPI code.

Maybe Charley Truax can fill you in better on this than I have.

Neil Moore, S.E.
neil moore and associates



At 10:28 AM 8/17/2005, you wrote:
>Is it valid to summarize that a simple and rectangular
>single-story hip roof structure with shear wall
>construction would probably not require any "truss
>permanent bracing"?  As I interpret it, the permanent
>bracing is the structural component(s) required to
>transfer loads (generally lateral) from one point in
>the structure to another through the roof trusses.  In
>this case, all lateral load goes directly to the
>diaphragm.
>
>I agree with the argument that in-truss bracing
>required to brace compression members from buckling is
>the responsibility of the truss manufacturer.
>
>An inspector has identified a building design plan as
>deficient because no such bracing is defined.  (The
>project was designed and detailed 100% by the
>architect, but that's another argument.)
>
>Regards,
>Jim Wilson
>
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