Uplift on concrete roof slab
Uplift on concrete roof slab
(OP)
I am looking at the design for a small storm shelter. For the roof system, I would like to use a 3 1/2" concrete slab over a metal deck. The design uplift exceeds the slab DL so I need to anchor the slab to the deck. I don't want to use studs on the joist because I would like to avoid composite action. Does anyone have a suggestion for attachment of the slab to the metal deck? Can I thru bolt the slab to the deck? Can anyone think of any potential problem with that?






RE: Uplift on concrete roof slab
The website below has tables for the effect of uplift on the shear strength of metal deck diaphragms but I don't think they have one listed as of yet for form deck with concrete. They are near the bottom of the page.
http://www.njb-united.com/usd/ddds.htm
RE: Uplift on concrete roof slab
RE: Uplift on concrete roof slab
Wind speed = 200 MPH (3-second Gust).
Importance factor = 1.0
Exposure = C
Directionality factor = 1.0
Internal pressure coefficient = +/- 0.55
Height of shelter is not restricted.
They also have the following requirements:
A) 6 to 12 inch CMU walls with #4 vertical bar fully grouted in each cell with horizontal reinforcement as required.
B) Reinforced concrete roof and wall sections at least 6 inches thick with at least #4 reinforcing steel at 12 inches on center each way.
I will let you extract the rest from the chapter. Here is a link to this manual:
http://www.fema.gov/fima/fema361.shtm
Regards,
Lutfi
RE: Uplift on concrete roof slab
1. try to add reinforcing steel in the slab so that it takes negative bending. You cannot simply rely on weight of slab to resist uplift! If you are going to do that, I would make sure that I have at least safety facto of 1.5 against uplift so I can go to sleep at night. Things are not always that simple.
Why are you opposed to composite action? It is a great system.
Regards,
Lutfi