40 foot round tank cover ideas 2

[TehMightyEngineer]

Got an interesting job and I'm interested if anyone has any good concepts on how to approach this.

Client has a 40 ft diameter concrete tank with an arched steel dome over it and is looking to replace the dome. The cover has to take large snow loads (~70 PSF ground snow) plus pedestrian loads. They got a price for an aluminum dome and it's fairly high so they're shopping around for alternative support structures.

So, I'm trying to come up with clever ways to do a precast structure that can be cost effective. We have a prestressing bed for slabs and small beams but it's limited to 18" depth. Any precast structural system ideas you folks think I should look at?

This is sort of the concept I was most leaning towards:

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[Gumpmaster]

Please post results from your estimate comparison. It doesn't seem like any of the ideas above would be much, if any, cheaper than a dome. I'm interested if they are.

 

[TehMightyEngineer]

Sure thing, I worked up a very rough estimate that had the cost around $60k. I got one of our estimators grinding out some numbers right now but given how this isn't a typical product for us it's going to take a few days to figure it out.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[canwesteng]

I think the precast dome with panels dumped into place is the only idea worth pursuing. All the other ideas are interesting and will get absolutely shredded by cast in place and structural steel at the bid phase.

 

[cal91]

Also keep in mind you can justify much lower snow loads with the dome than a flat roof system.

 

[TehMightyEngineer]

Please post results from your estimate comparison. It doesn't seem like any of the ideas above would be much, if any, cheaper than a dome. I'm interested if they are.

We finished our estimate at $55,000 delivered cost so we're $20,000 cheaper than what they were quoted for an aluminum tank dome. Obviously some things aren't 1:1 as we'll need a bigger crane to set our pieces versus the aluminum dome.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com