Axial force in joists and joist girders from wind load
Axial force in joists and joist girders from wind load
(OP)
Hello,
I'm working on a 420'x120' warehouse building made of precast concrete walls. There is one row of columns in the middle of the building, and the metal roof deck is supported by joists at 5' ctrs. The joists span 60' between the wall and the joist girders (which span between the columns).
I calculated the axial force in the joists and the joist girders using this: (wind pressure)*(wall height)/2*(tributary width) where the tributary width was 5' for the joists and 60' for the joist girder. The axial force this gives seems very high to me and I am wondering if I am looking at this incorrectly. Any help would be appreciated! Thanks!
I'm working on a 420'x120' warehouse building made of precast concrete walls. There is one row of columns in the middle of the building, and the metal roof deck is supported by joists at 5' ctrs. The joists span 60' between the wall and the joist girders (which span between the columns).
I calculated the axial force in the joists and the joist girders using this: (wind pressure)*(wall height)/2*(tributary width) where the tributary width was 5' for the joists and 60' for the joist girder. The axial force this gives seems very high to me and I am wondering if I am looking at this incorrectly. Any help would be appreciated! Thanks!






RE: Axial force in joists and joist girders from wind load
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Axial force in joists and joist girders from wind load
RE: Axial force in joists and joist girders from wind load
RE: Axial force in joists and joist girders from wind load
Dik
RE: Axial force in joists and joist girders from wind load
DaveAtkins
RE: Axial force in joists and joist girders from wind load
RE: Axial force in joists and joist girders from wind load
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Axial force in joists and joist girders from wind load
RE: Axial force in joists and joist girders from wind load
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Axial force in joists and joist girders from wind load
https://www.aisc.org/globalassets/modern-steel/arc...
Eric McDonald, PE
McDonald Structural Engineering, PLLC
RE: Axial force in joists and joist girders from wind load
In the past, I HAVE put axial forces and end moments on the drawings for the joist supplier--when the joist is part of a rigid frame or is a drag strut (collector) carrying a significant axial force.
Now, I also think the steel deck, when it spans parallel to the wall, CAN take diaphragm force. We tend to think, "How can a deck take axial force perpendicular to the deck span? The deck is flimsy in that direction and will crumple." But it is a SYSTEM, and the joists and deck work together to receive and transfer diaphragm forces.
DaveAtkins
RE: Axial force in joists and joist girders from wind load
I'm solidly in that camp.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Axial force in joists and joist girders from wind load
Can you then explain the reasoning behind the deck suppliers not indicating a lower diaphragm strength or stiffness depending on direction of deck?
RE: Axial force in joists and joist girders from wind load
You're talking about two different things.
There is a difference between:
1) Compression forces applied to a deck in its plane (how the force gets into the diaphragm)
vs.
2) Shear capacity and stiffness for overall diaphragm distortion (how the diaphragm resists the shear in-plane where shear capacity and stiffness are non-directional).
Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies
RE: Axial force in joists and joist girders from wind load
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Axial force in joists and joist girders from wind load
I envision the whole accordion type failure, but if I specified angles at 6 ft o/c in the first joist space I would get crucified.
RE: Axial force in joists and joist girders from wind load
DaveAtkins
RE: Axial force in joists and joist girders from wind load
You're talking about the case where the joists run parallel to the wall, right? If so then, like you, I normally would let the deck take the load in compression unless the loads were just too high for that. If the loads were too high for that path then, yes, I'd throw some hss in the flutes for the first joist spacing or two. And it would be unpopular. No accordion action either way though.
Me too but I'll assume that the angle, or the top of the wall itself, is spanning out to the joists with the deck giving way accordion style.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Axial force in joists and joist girders from wind load