Net uplift on metal deck on bar joists

[JoeBaseplate]

What are the major effects of net uplift on a roof deck? I know that I have to show the net uplift on the documents for the joist mnfr to design for, which will end up in extra bridging lines. But what other major issues should I be concerned about? I believe that the 22 ga metal deck connection to jsts should be OK.

The roof slope angle is less then 3 degrees, there is no ballast.

 

[frv]

If your roof is light enough, you may have uplift on your interior footings/piers. Especially in high wind zones.

There is also shear/uplift interaction on the metal deck and sidelap fasteners.

 

[SteelPE]

I believe the metal deck profile is almost symmetrical, so as long as it is properly attached then you shouldn't have a problem with the metal deck.

We usually just specify the uplift on the design drawings and let the mfr figure what needs to be done to the joists. Like you said, they will add the extra bridging to the system as needed. I will say though, that I have never designed a roof over 120mph so I don't really know if there are any other problems at higher wind speeds.

 

[JoeBaseplate]

frv, my bearing walls are precast and masonry, so uplift on the footings is not an issue.

SteelPE, I am in 90 mph zone (IL).

Thanks for the input.

 

[SteelPE]

other than making sure your anchorage can take the load I believe there isn't much else to it.

I always have a tendency of making things way more complicated than they need to be.

 

[steellion]

The Net Uplift is indicated on the drawings for the joist/truss designers' information. If your joists are bearing on steel beams, make sure you check the beams for uplift at the unbraced length of the bottom flange, which will often be a critical case.