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Re: Truss permanent bracing

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In El Dorado County, you won't get a building permit issued (in most cases) without the permanent bracing design provided. On our last project (a winery) we hired a truss engineering consultant to design the trusses up front. This can be a real hassle for lots of firms and owners.

Might mention that this is also a problem with fire-sprinkler systems. Sacrament County wrestled with this a number of years ago, but I don't know what got resolved.

Another issue may be having a mechanical consultant who designs his equipment and you take care of his weights and locations in the structural design only to have the owner ignore the mechanical consultant and get a mechanical contractor in to do his own thing - like different locations and possible greater weights on your roof trusses. You might even be lucky to find out about it.

Neil Moore, S.E.



At 12:32 PM 8/17/2005, Jordan Truesdell, PE wrote:
I've yet to see a shop drawing submission that does not include language to the effect that the manufacturer adheres to the TPI requirements, aka no truss bracing. Most show locations of bracing, but no overall plan. A horizontal bracing member merely insures that all the similar webs in a line will fail together. Since slender members are based on the minimum thickness, and that is universally 1.5", the architectural design (pitch+span) will tend to force the webs beyond the slender point. Aside from going to n-ply trusses all over the building (can you say "unhappy owner"?), they're limited by the geometry given. I think you at least need to give them bracing points and allowable values on the structure if you expect them to even try to brace. My guess is that this is an unwinnable battle for individual firms using notes. Sadly, we (SEs) are not nearly as organized as the TPI when it comes to forcing this issue to the ICC.

Andy Heigley wrote:

We have talked about this several times in our firm about this topic.  And
finally resolved to state in our General Structural Notes and specs, to
specifically state something to these effects:

THE DESIGN OF ALL WEB MEMBER PERMANENT BRACE SIZES AND CONNECTIONS, REQUIRED
FOR THE STRUCTURAL ADEQUACY OF THE TRUSSES, SHALL BE THE SOLE RESPONSIBILITY
OF THE TRUSS SUPPLIER.
ADDITIONAL MEMBER PERMANENT BRACE SIZES AND CONNECTIONS, NOT PROVIDED BY THE
SHEATHING SHOWN ON THE CONSTRUCTION DRAWINGS, SHALL ALSO BE THE
RESPONSIBILITY OF THE TRUSS SUPPLIER.  THIS BRACING CAN INCLUDE, BUT IS NOT
LIMITED TO, TOP CHORD BRACING FOR TRUSSES WITH PIGGY-BACKS, AND INTERMEDIATE
BRACES FOR GABLE TRUSS WEB MEMBERS.

It is the Truss designer's choice to use a slender member.  If he wants to
use a slender member and brace it so it works, then he should provide the
bracing for it.  So far, we've had no arguments from truss suppliers
regarding this note, and I'll even say I've checked shop drawings that calls
out the bracing for web members.

So that's my 2 cents.

Andy Heigley, PE

Dublin, Ohio



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