Cantilever Diaphragm
Cantilever Diaphragm
(OP)
I have a metal deck diaph. w/ conc. shear wall bldg.
As we all know the chord force in a simple span diaphragm is (wl^2/8)/(bldg depth). For a cantilever diaphragm, I have shear walls on 3 sides. At first I thought the max chord force would be (wl^2/2)/(bldg. depth), just like in a true fixed cantilever beam. The force is assumed to be transferred all the way through the roof, the roof starts to deflect, and then it gets into the 3 sidewalls.
But then I thought about the concrete shear walls acting to take the T/C couple all the way down the bldg length, and the moment wouldn't reach wl^2/2 at the end. The rotation is taken out immediately along the length. Or maybe I am being stupid and thinking too much again.
As we all know the chord force in a simple span diaphragm is (wl^2/8)/(bldg depth). For a cantilever diaphragm, I have shear walls on 3 sides. At first I thought the max chord force would be (wl^2/2)/(bldg. depth), just like in a true fixed cantilever beam. The force is assumed to be transferred all the way through the roof, the roof starts to deflect, and then it gets into the 3 sidewalls.
But then I thought about the concrete shear walls acting to take the T/C couple all the way down the bldg length, and the moment wouldn't reach wl^2/2 at the end. The rotation is taken out immediately along the length. Or maybe I am being stupid and thinking too much again.






RE: Cantilever Diaphragm
All loads parallel to the single wall form a moment with their reaction, which has to be resisted by a force couple in the double walls.
I have kept this simple, trying to avoid confusion.
Good Luck,
Fred
RE: Cantilever Diaphragm
RE: Cantilever Diaphragm
There are no chord forces in a three sided diaphragm. As you stated, the moment is resisted by the two shear walls perpendicular to the direction of the applied force.
DaveAtkins