tank roof uplift

[sme75]

Is it typical to dsign for an uplift, due to wind, on the roof of storage tanks? API 650 and AWWA D-100 do not seem to address the topic, they just give a formula for the lateral load. In fact the anchorage calculations in section 3 of API 650 do not include an uplift due to wind in table 3-21b. If you have used an uplift design force, what have you used to calculate the force? Thanks for any ideas.

 

[JoeTank]

Just so everyone is clear about API-650. What has just been published is the fourth addenum to the Standard, not a new edition. A new edition is expected to be published later this year.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[IFRs]

Steve - Are there more changes to 650 beyond Addendum 4?

 

[JStephen]

Well, I got in the Addendum 4 and started playing with it. I think the wind uplift/overturn part is totally screwy.

Specifically, the wind uplift is larger than the normal dead weight of a roof. For the overall tank to be unanchored, you need a certain amount of shell weight to anchor the roof. So, for example, my design shows me that a 50' diameter by 16' high tank is not stable for wind uplift/overturn, whereas a 50' diameter by 56' high tank is. (If you want to check, I'm figuring 1/4" shell in both, 3/16" roof plate, 2,400# supported rafter weight, no internal pressure, 120 MPH 3-second gust.)

I'll send a note in to API, but I can't imagine that this is the intended result of the design procedure.

 

[carthago]

If this addendum is correct and I hope not (entirely)
then we will have anchor bolts everywhere!!!
--------------------

Just for the record I have noticed on an old german standard for storage tank (DIN 4119- part 2)
a nice sketch with the uplift do to wind with a wind uplift pressure equal to 0.6 * the horizontal wind pressure.

The skectch is a a dome roof.