Brace Free Trusses?
Brace Free Trusses?
(OP)
Some local truss companies are offering "brace free trusses." Is this possible? It looks like they are adding a 2x4 block to the compression members to eliminate a brace. But if memory serves me correct, 1.5" thick lumber in compression has a length limit that requires a brace no matter how wide the lumber is. Has anybody seen this or questioned this?





RE: Brace Free Trusses?
RE: Brace Free Trusses?
Dik
RE: Brace Free Trusses?
Also, sometimes bumping the web material grade from SPF #2 up to MSR can eliminate the need for bracing. Lumber costs a little more, but saves the contractor time in the field.
RE: Brace Free Trusses?
members, the maximum unbraced length is 93.75", regardless if it is 2x4, 2x6, 2x8, etc., or if it has a Web-Block applied to it. This requirement is specified in Chapter 3 of NDS-2001 and is referenced by the ANSl/TPl 1-2002 truss design standard. So in other words, the Alpine web block does not work on webs over 93.75 inches long, and a brace is still required. Yet I have drawings with webs over 132 inches long in compression, with the web block added, and no brace is on the engineering.
RE: Brace Free Trusses?
I am not sure what you are refering to as a web-block, but if it is a 2x nailed flat to the compression member and full length of it, the max length would be 50*width. So 175" for a 2x4. If the member is is bracing is also a 2x4, then 175" is also the limiting slederness length of it.
RE: Brace Free Trusses?
I=0.8Lu
I/d < 80
I < 80 * d (or 80 * 1.5")
I < 120"
I = 0.8Lu < 120"
Lu < 120" / 0.8 = 150"
Looks like the limit is 150" so 132" is OK
RE: Brace Free Trusses?
See the link i posted above to see what Web-Block is.
RE: Brace Free Trusses?
RE: Brace Free Trusses?
RE: Brace Free Trusses?
I looked at a hotel that was about 5 years old that had insufficient bracing. Several compression members were braced horizontally to each other - they ALL buckeled together. The roof didn't fall down because of the interior partions.
I would be nervous too. Are you the structural engineer for the job?
RE: Brace Free Trusses?