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RE: Question on wood Roof Trusses

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We are generally saying the same thing.  We specify the loads, truss
locations, truss bracing and connections of truss to supports.  The truss
designer designs the trusses themselves and the truss to truss connections.
For what it is worth we also specify the top and bottom chord material since
this has an impact on the diaph. capacities.  And specify vertical and
lateral deflection limits because industry standards are not always
appropriate for service or with respect to expansive soil movement.  But
that is all another long story. 

We do look to more than loading when we review the truss drawings.  In
particularly we look to see that they roof designer has not changed the
layout of the trusses as this impacts headers, top plates (see previous
string on this subject) and foundations.


-----Original Message-----
From: Structuralist [mailto:dennis.wish(--nospam--at)]
Sent: Friday, January 12, 2001 1:22 PM
To: seaint(--nospam--at)
Subject: RE: Question on wood Roof Trusses

I believe that the truss documents require the EOR to design the brace based
on the information provided by the truss designer:
>From WTCA 1-1995:
Section 3.2.4
[The Building Designer must design)
"Permanent bracing design for the structure including the Trusses, except as
provided in 3.4 and 6.2.12."

Section 3.4
"Specify permanent lateral bracing where indicated by the Truss Designer on
the Truss Design Drawings, to prevent buckling of the individual truss
members due to design loads. The Building Designer shall specify how the
permanent lateral bracing is to be anchored or restrained to prevent lateral
movement if all truss members, so braced, buckle together. This is
accomplished by: (a) anchorage to solid end walls; (b) permanent diagonal
bracing in the plane of the web members; or (c) other means when
demonstrated by the Building Designer to provide equivalent bracing."

What I interpret this to mean is that the brace is to be designed by the
Building designer based on the information provided by the Truss Designer.
The Building designer does not make the determination at which point the
brace is to be applied or need not calculate the lateral load to the brace -
only to size and detail the installation of an adequate brace.

Maybe we are saying the same thing, but I don't see how the Building
designer becomes responsible for any more than the actual design of the
brace member.


I also believe that there is a forthcoming change in the specification for
responsibility that is not covered in 1-1995 but I am not too sure about
this one.

Dennis S. Wish, PE


-----Original Message-----
From: George Richards, P.E. [mailto:george(--nospam--at)]
Sent: Friday, January 12, 2001 8:45 AM
To: 'seaint(--nospam--at)'
Subject: RE: Question on wood Roof Trusses

Metal plate connected wood truss industry documents provide that the
building designer specify permanent chord bracing, not the truss designer.
Basically the truss design only is responsible for the trusses and the truss
to truss connections.  Neil Moore is correct.

George Richards, P. E.

-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)]
Sent: Friday, January 12, 2001 7:30 AM
To: seaint(--nospam--at)
Subject: Question on wood Roof Trusses

"...  Any compression member with L/d > 50, i.e., 75 inches for 2X
nominal members, has to have intermediate bracing *detailed by the truss
designer* as this is a condition of design.  ..."