Simple diaphragm with interior wall interruption

[StrEng007]

What happens to the chord forces in a flexible roof diaphragm when an interior partition wall interrupts the diaphragm?

Is the chord force still wB[sup]2[/sup]/8L for the windward and leeward walls only (see diagrams)?

Or, are there now two sub diaphragms, one for the windward side of the building and one for the leeward? If so, how does the center wall act as both a compression and tension chord at the same time?

 

[DaveAtkins]

I think you need to create a chord on each side of the party wall. It could be as simple as continuous blocking with Simpson straps at the splices.

DaveAtkins

 

[sponton]

Yes, you have two different diaphragms and two different chord sets. what you can do is basically design the windward one for only the windward pressure and then the diaphragm for leeward forces. Check the book The Analysis of Irregular Shaped Structures and diphragms by terry malone.

 

[KootK]

Is the chord force still wB2/8L for the windward and leeward walls only (see diagrams)?

That one for me. If the interior wall is block, you can just transfer the shear across the wall with conventional connection detailing and then pretend it's not there for the sake of chord design. Deck bearing angles bolted to the interior wall or whatever. You want some kind of capacity to drag tension across the interior wall however so keep that in mind.

The sketch below shows the forces that the diaphragm would be assumed to exert on the walls. Note that they cancel across the interior wall.

You could break it up into sub diaphragms but that's not what my first choice would be.

 

[StrEng007]

sponton,
Off the top of your head, do you know how you'd approach the chord force at the interior wall? For the windward side it goes into tension, for the leeward side it goes into compression...

 

[StrEng007]

KootK,
OK, that is more in line with what I was thinking. It would effectively cancel as though its the N.A. of the deep beam.

 

[KootK]

Is this steel and fluted deck or wood trusses and panel sheathing?

 

[StrEng007]

Wood truss with wood structural panels.

 

[KootK]

With wood, you'll need to work a little harder to drag some tension across the interior wall as I mentioned previously.