Rectangular Underground Steel Shelter

[NewbieStruct]

I have steel tank that is made of a 12 gage steel. I am trying to understand how to design this. Do I use thin plate theory with three sides simply supported or is FEA the way to go? If FEA, then is STAAD or any other software capable of doing the same?

 

[JedClampett]

IMHO, if you have a 12 gage metal walled tank filled with water or underground, it's going to fail and fail in a big way. Underground structures are almost always made of reinforced concrete.

 

[msquared48]

Unless it is in a very dry desert environment, seldom seeing any water, the steel will eventually corrode and fail as Jed alluded to. The acidity of the wet soil will assure that.

Use reinforced concrete for your shelter.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[MiketheEngineer]

How big is the tank?? What kind of soil - how deep?

12 gauge is not much thicker than a highway sign - only .105''

 

[nuche1973]

I am assuuming a rectangular tank. If so then start with simple bending theory on a 12" section, to get your maximum span. However,you didn't post what you storing, dimensions, soil type, material (304L, A-36, etc.) soil pressures, or if you plan using stiffeners.

Not all underground storage tanks are concrete: fuel tanks are steel and I've seen stainless steel water tanks, small ones. We need more information on your question.

There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.

 

[a2mfk]

Guys- this is a classic poor post, we have no idea what this is, could be fish tank for his house...

 

[ToadJones]

Most fish tanks I had as a kid were made of glass with silicon caulking at the corners. The design was super simple.

 

[NewbieStruct]

Sorry, guys, I had mentioned in the heading that this is a rectangular underground storm shelter. I should have mentioned it within the post.

This is a feasibility study. Our client has asked us to look at the possibility of use of 12 gage steel (he has that in surplus). He got the idea from a storm shelter he saw in Europe. He wants to look at possible height, length and depth combinations that we could use to do the same.

We have already informed him that it might not work. But, I wanted to make sure that I approach this correctly.

I think I have figured out how to design it against floatation. I am was planning to add concrete strips at the bottom. (like a manhole with an extended base). Rebar could be welded to the sides of the tank so that the concrete and the tank are together. The client is fine with that.

The one size he wants us to look at is 48" deep by 72" long by 36" wide. I might be able to persuade him to use stiffeners.

We are looking to design it for soil pressures.I was planning to use an active soil pressure of 60 pcf. If you need anything more let me know

 

[MiketheEngineer]

Why don't you just buy a coffin and go with that?? About the same size and you could just leave it if the customer dies...

Is this for a bunch of midgets or just one or two hunched over people??

 

[NewbieStruct]

Well the client said people generally sat down on small stools within the tank. And this was specifically for a family four.

 

[ornerynorsk]

Deeply forming or corrugating the sidewalls,and ceiling, or some other form of stiffening is going to be a must, as is mitigating the corrosion problem.

It can certainly be done, you've just got a number of challenges to work around given the material constraint.

If this is a storm shelter, do you need to calc in additional loads (ie:falling debris) or plan for water issues, as well?

I've seen people build bomb shelters and storm shelters out of corrugated culvert piping, with reasonably satisfactory results.

Good luck.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[nuche1973]

First, I'd start with FEMA 320 for the requirements of storm shelters, especially for the door and your load factors. If this thing is going to be certified then you have to meet the requirements in this document.

Second, you'll need to investigate the lateral effects on your plate. I don't see how you can design this with out stiffeners. I saw test results on a similar type structure,but above ground. The whole thing was double walled with steel channels. The lab that tested it highly recommended hearing protection, go figure. AISC 13th, chapter B4 will give you a guideline for stiffened elements and effective width.

I always find it interesting how the average joe preceives how we design structures. Putting a steel box in the ground is just as complicated as having it above ground.

There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.

 

[MiketheEngineer]

Don't forget ventilation, wiring, communication, and drains??

How do you break out if the door gets jammed??

 

[nuche1973]

I beleive that is addressed in FEMA 320. Although, come to think of it, I may have the wrong book, it could be FEMA 361.

There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.

 

[NewbieStruct]

Nuche is right, it is FEMA 361. The client is ordering special sliding lids (covers) on top that are FEMA approved for missile loads.

I still trying to look at resources that could design the plates.

 

[a2mfk]

Man I hope you guys got cash up front or a retainer for this seemingly ridiculous idea. Not to rain on your parade (no pun intended) but that is why you are getting the responses you are getting from these guys. Sounds like you have an ill-informed client who is dreaming, which is fine if he is paying you for this silly little exercise.

By the time you add all the steel necessary to make 12ga work, supports at 4" o.c. or whatever, it will cost about 10k to fabricate... They sell these pre-cast, reinforced concrete bomb/storm shelters (MS squared said it first) for a fraction of the cost since they are glorified box culverts and can be cast in those types of plants (google it, you'll see they are all over). Pretty easy to make 8-12" of reinforced concrete meet your bending stress and impact resistance requirements.

 

[NewbieStruct]

Well he is paying us for this idea (actually we already have got paid some amount). He has high hopes of building this shelters since they have been built in Europe and plus he tells us they have been used in his houses and friend's houses in TX. The city out there did not require a structural stamp to make it work. The missile load test on structure was sufficient.

He is a long time client and this economy we just dont want to displease him. If I can figure out a methodology to show it does/does not work I think we will be good. I trying to get in grips with what method should I adopt to actually design it.

 

[dhengr]

Did the missile test involve an ICBM or a 2"x2"x6" piece of balsa wood as a missile? I’d just go with the missile testing thing, ask them what they did, since that was sufficient. When you are a rocket scientist you don’t need an engineering stamp, all’s ya need is lots of govment money.

 

[msquared48]

If this is a tornado shelter, it will be sucked right out of the ground as light as I envision you want it to be. I strongly recommend a concrete structure.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[IDS]

Personally I prefer concrete for underground structures, but there are plenty of corrugated galvanised steel arch structures, and they can be quite large. A flat steel sheet rectangular structure on the other hand will have a very small size limit, unless you put in a lot more steel in the form of stiffeners.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/