Limitations on a Cantilevered Metal Deck Diaphragm

[abusementpark]

Where can I find what the limitations should be on a cantilevered metal deck diaphragm? Also, what about the special case of a three-sided structure with an open wall (i.e garage) ?

I've seen limitations on these situations for wood diaphragms in the wood SDPWS, but I haven't come across anything that addresses metal deck diaphragms. I looked in the deck diaphragm design manual, but didn't see anything on limitations.

 

[ishvaaag]

I am not sure if I am answering your question but you can find shearwall plf capacities for corrugated steel sheet walls used against wind and earthquake in table 5 of

http://www.tippingmar.com/uploads/documents/casestudy/metalwalls_Research_Report.pdf

 

[MiketheEngineer]

Not sure if I ever have either.

You could reverse engineer it. Find out max moment for single span, then calculate overhang to match that moment. Probably knock off 20-25% so you can sleep at night.

 

[ron9876]

I don't think that I have ever seen any limatitions for steel deck diaphragms like wood diaphragms have. If the shear in the deck,the forces in the chords and deflections all work I don't see a problem with a cantilevered steel deck diaphragm. I would guess that the deflections would be a problem if there is much of a cantilever.

 

[abusementpark]

Is there anything that says you have to prove that it can be classified as a rigid diaphragm for it to cantilever?

 

[abusementpark]

If the shear in the deck,the forces in the chords and deflections all work I don't see a problem with a cantilevered steel deck diaphragm. I would guess that the deflections would be a problem if there is much of a cantilever.

Where would you get your deflection criteria?

 

[ron9876]

abusementpark you have a good point there. Always amazes me that we can have such detailed codes on forces such as wind loading but the codes won't establish limits on drift/deflection.

What is the drift criteria for a high rise with wind only?

 

[RFreund]

I think this is a good topic in general. I thought there would be more information in regards to cantilevered metal roof deck but there does not seem to be much. I came across these same questions and I even tried contacting Vulcaft/Nucor but they did not have much to offer me.

I mean you can design for shear plus the force from the T/C couple due to moment but I'm not sure how to check against deflection/stiffness.

A solid example for this situation would be great.
Let us know if you find anything.

EIT

 

[asixth]

I never use corrugated metal sheet to cantilever. Admitted I never specify anything greater than 0.02" thick. I would provide strapping to the steel frame.

ron9876,

there are deflection limits for earthquake events. It is something like height/100 for the real actions (not including force reduction because of ductility).

 

[RFreund]

I have not read any of this reference however I have heard that it does a good job of getting in to the details of diaphragm action:

MCA (Metal Construction Association) "A Primer on Diaphragm Design"

EIT