Maximum Metal Roof Deck Diaphragm Aspect Ratio?
Maximum Metal Roof Deck Diaphragm Aspect Ratio?
(OP)
I am wondering if there is any published recommendation or requirements for maximum unfilled metal roof deck diaphragms. I know for plywood diaphragms, the codes limit it to 4:1 aspect ratio. But I can't find any similar limit for metal deck. There is a discussion going between the engineers in my office about the acceptibility of a 4.3:1 roof diaphragm. We can size the deck and fasteners for the required strength and stiffness, but some are concerned it is just too long and narrow.
Also, is there any recommendation for maximum diaphragm deflection limit? I limit my diaphragm deflection to ensure that the maximum story drift for the columns at mid-span of the diaphragm is not exceeded.
Thanks in advance.
Also, is there any recommendation for maximum diaphragm deflection limit? I limit my diaphragm deflection to ensure that the maximum story drift for the columns at mid-span of the diaphragm is not exceeded.
Thanks in advance.






RE: Maximum Metal Roof Deck Diaphragm Aspect Ratio?
Thanks.
RE: Maximum Metal Roof Deck Diaphragm Aspect Ratio?
Have you checked the chord forces? They may be quite large for a long, shallow diaphragm.
DaveAtkins
RE: Maximum Metal Roof Deck Diaphragm Aspect Ratio?
RE: Maximum Metal Roof Deck Diaphragm Aspect Ratio?
As DaveAtkins mentioned, your chord forces will be very high as well (although all you need to do is bump up your deck angle.
But I don't think there is any code-imposed aspect ratio limit.
RE: Maximum Metal Roof Deck Diaphragm Aspect Ratio?
I work with steel clad post frame type construction
RE: Maximum Metal Roof Deck Diaphragm Aspect Ratio?
As a warning, these tables are very difficult to comprehend. Whenever I try to explain them, I end up confusing myself and who I'm talking to.
RE: Maximum Metal Roof Deck Diaphragm Aspect Ratio?
But in this case, this was not possible. I can get everything to work fine, chord forces, deflection, diaphragm capacity, combined uplift/shear etc... The deck connections are pretty robust, 36/7 w/ 11#10 TEKS sidelaps using 18 gage 1.5" B deck, but everything works.
I just wanted to verify that there were no code limits that I was not aware of.
Thanks again.
RE: Maximum Metal Roof Deck Diaphragm Aspect Ratio?
RE: Maximum Metal Roof Deck Diaphragm Aspect Ratio?
RE: Maximum Metal Roof Deck Diaphragm Aspect Ratio?