Wood Prefabricated Truss used as a drag strut
Wood Prefabricated Truss used as a drag strut
(OP)
Is a "drag truss" a truss in which the bottom chord is designed to accomodate tension/compression loads due to lateral loads in addition to tension/compression induced by vertical loads? My friend, a structural engineer, specified a "double drag truss" to be used in a single family single story home and the truss company said they had never heard of this.
Just curious....
Just curious....





RE: Wood Prefabricated Truss used as a drag strut
RE: Wood Prefabricated Truss used as a drag strut
Trusses spaced at 16" or 24" would result in much smaller loads and using Simpson type anchors to fasten the truss to the top plates would maked specifying nail patterns for plywood much easier.
Could this be one of the emperical mechanisms working to support windloads prior to the development of engineered diaphrams?
RE: Wood Prefabricated Truss used as a drag strut
I know there is a good reason for them, I just dont think that they are being applied properly.
Example .. 8000# drag load on a 14-0 gable ??? give me a break. So if I understand it right, that means that the forces transfered throught the roof as a whole into the gable will amount to 8K in drag force ? 4 tons +/- ??
come on now !!
JP
General Manager (now)
Truss Designer (10+ years)
RE: Wood Prefabricated Truss used as a drag strut
The idea of the roof diaphram is to get the loads out to a shear wall such that you can then transfer the loads to the foundation. Using the trusses to transfer all of the wind load essentially puts the loading right back into the top of the wall.
There must be some diaphram action to get the roof loads out to the shear walls.
RE: Wood Prefabricated Truss used as a drag strut
RE: Wood Prefabricated Truss used as a drag strut