Trusses are continually braced by the roof sheathing along their top chord since that is your typical compression chord under most everyday loading. The bottom chord will be in compression once there is uplift on the trusses due to windows/doors blowing out during a wind event. Thus, blocking/bracing of the top of interior/non-bearing and gable end walls back up to the diaphragm.
The fact that the truss designer/manufacturer is saying the truss is braced by a gyp board ceiling is not the same as the the truss being braced for stability. In that case, the ceiling is providing just enough lateral support to maintain the truss plumb and vertical, and that's all it's doing.
You do have relatively light loads, but I wouldn't necessarily rely on sheetrock to laterally braced to top of wall, unless you specifically detail it to do so.
On Wed, Dec 7, 2011 at 1:50 PM, <firstname.lastname@example.org> wrote:
Jeff:If it makes you feel any better, I have also called lateral bracing on top of the shear walls, under the roof trusses. Not all the time though. Depending on the truss height, wall shear, etc.
Farzin S. Rahbar, SEVice President
David C. Weiss Structural Engineer & Associates, Inc.
From: Jeff Hedman <email@example.com>
To: seaint <firstname.lastname@example.org>
Sent: Wed, Dec 7, 2011 12:53 pm
Subject: RE: Interior wood shear wall lateral bracing
Oshin and David,The truss bracing in this case will be a sheetrock ceiling. It will be attached to the trusses how they typically would do it. They would probably have blocking nailed to the top of the wall and the sheetrock would be screwed to that. So, yes, it would fall within the length of the wall. But the actual connection is probably a guess unless I specified it. In the interest of time I have already resubmitted the plans with the bracing shown on the drawings. I just wanted to know others thoughts on it because in my area I have yet to see this bracing specified, let alone installed. It's hard enough to get gable end bracing installed. Thank you both for the feed back. Although I may not be 100% convinced, it looks like I will be specifying the bracing from now on.Jeff
David Topete, SE