Cantilevered Vierendeel Truss
Cantilevered Vierendeel Truss
(OP)
I am brain storming on a new project. The architect is a moving target so the details are wide open. Essentially there is a 20' to 24' cantilevered vierendeel truss carrying residential deck (60psf LL) and a low roof (40psf LL). The dead load is conventional light frame and a significant portion of the deflection is from live and snow loads.
The truss backspan is continued into the main house and a question about vibration has been raised, both from human activiy and wind.
Does any have down and dirty numbers and or a resource regarding a similar situation. See attached pic for clarity.
Thanks
The truss backspan is continued into the main house and a question about vibration has been raised, both from human activiy and wind.
Does any have down and dirty numbers and or a resource regarding a similar situation. See attached pic for clarity.
Thanks






RE: Cantilevered Vierendeel Truss
RE: Cantilevered Vierendeel Truss
You are out on the edge a bit here.... Can it be done - sure - but a LOT of analysis will be required.
Wind uplift, snow, moving people, vibrations, deflections, etc....
Good Luck
RE: Cantilevered Vierendeel Truss
For regular residential building with carefully selected flooring material, unless a dancing hall is included, I don't think vibration is a problem simply from human activities. But, depending the region, wind could be a concern if the structure is too flexible. Check out articles on wind engineering should help.
Beware of stress reversal on the trusses, and uplift on the connections.
RE: Cantilevered Vierendeel Truss
Your floor is probably 12' deep and your cantilever is 25' and all you really need is continuous chords.
Again, I don't know if door openings are a concern.
RE: Cantilevered Vierendeel Truss
You are going to need some horizontal sway bracing too, not just the
Hokie - think Phalinx... screw the choke.
Mike McCann
MMC Engineering
RE: Cantilevered Vierendeel Truss
Mike McCann
MMC Engineering
RE: Cantilevered Vierendeel Truss
I didn't even know what that was until I looked it up. I take it you mean Phalanx. But I think that's overkill (sorry, I mean excessive) even for an architect. An old fashioned scattergun should do just fine.
RE: Cantilevered Vierendeel Truss
Mike McCann
MMC Engineering
RE: Cantilevered Vierendeel Truss
I have a few types of preliminary models running some in RISA some in IES.
The Vierendeel truss is not the only option. The client was surprised with some of the initial sizes so we are presenting a few other options today. One option is a diagonal brace down from the 1st floor deck (out near the end of the catilever) and the other is a 'V' shaped cantilevered truss.
Back checking model results with a hand approximate method will be my challenge.
RE: Cantilevered Vierendeel Truss
RE: Cantilevered Vierendeel Truss
The beam is afterall basically a multi story portal frame on its side.
RE: Cantilevered Vierendeel Truss
You are right, I was giving approximations based on a regular truss, however it will not be appropriate for a vierendeel.
A 0.85 factor is used to account for web shear deformations in a regular truss (i think i have seen that recommendation in joist catalogs and composite joist publications by AISC)
RE: Cantilevered Vierendeel Truss