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Wood Truss Gable End Bracing (piggy back condition)

Wood Truss Gable End Bracing (piggy back condition)

Wood Truss Gable End Bracing (piggy back condition)

(OP)
I have a project where the roof trusses need to be constructed with piggy backs due to their height.  The roof is also configured so that this piggy back condition occurs at the gable end of the building.  Typically, I show the standard MiTek gable end bracing details.  However, because the overall height of the truss (17' from bearing to peak) and that truss is in two pieces, I'm unsure as to how to brace the gable end.  If I use the standard bracing detail, the diagonal brace could be up to 22' long.

Any assistance or input would be greatly appreciated.  Oh, the project is located in central Florida.

Thank you!  

RE: Wood Truss Gable End Bracing (piggy back condition)

For this condition I would require the trusses to have verticals at the braces. Nail the brace to each vertical and provide a lap splice detail, splice the brace with a lenght of 2x.

Garth Dreger PE
AZ Phoenix area

RE: Wood Truss Gable End Bracing (piggy back condition)

(OP)
woodman88,

Thank you.  I think that I'll lean towards that way.  I may actually detail an "I-brace" detail rather than just a T or L-brace.

Thanks,

RE: Wood Truss Gable End Bracing (piggy back condition)

bsh117...post a detail of the truss layout. Potential high wind condition, so diagonal bracing is important.

RE: Wood Truss Gable End Bracing (piggy back condition)

Be sure the common trusses at the opposite end of your bracing are designed for the additional loads.

RE: Wood Truss Gable End Bracing (piggy back condition)

Y0ou should be bracing back to the roof diaphragm and to blocking placed between two trusses just under the diaphragm.  The trusses will have to take the uplift from the brace, but not the lateral kick.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Wood Truss Gable End Bracing (piggy back condition)

At that height your going to have trouble properly bracing the gable end.  I suggest a bottom chord diaphragm using OSB sheathing.  The sheathing should extend so that it has a 2:1 ratio though some will argue that 4:1 is appropriate.

The problem with simply running kickers up to the roof is that it has a vertical component also.  Thus the trusses need to be designed for an extra gravity and uplift wind loads.  Good luck getting the trusses designed for that as most manufacturers rubber stamp everything.  Plus you'll have to connect the trusses for the greater uplift load as well.

If you use X bracing then the trusses become chords for a cantelever beam that spans from the diaphragm downward.  The bracing acts as the web members.   

John Southard, M.S., P.E.
http://www.pdhlibrary.com

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