Design/Analysis of Steel Rectangular STP Tank

[Piper30]

I'm an Enviro Eng who knows about about sizing the tanks already but needs to tackle the analysis and structural design of steel tanks for a project. I am accustomed to designing reinf conc. tanks but have had very little experience with steel. And it's been a while since college. Does anyone know any good quick concise books or resources to study up on this? When you google all you get is water tanks on towers and undergroung fuel tanks.

 

[Piper30]

PS- The tanks are open top mostly underground (only a ft or two above grade)

 

[chicopee]

M.E. handbooks have deflection and stress equations for flat plates simply and rigidly supported. If deflections seem too high you may want to reinforce the outside or inside of tanks with channels or angle iron bars. That is where I would start. Of course you may have regulatory conditions that you may have to abide with.

 

[ATSE]

1. Below grade steel tank is not a good idea. There are many that make their living replacing underground steel tanks - primarily due to failure of coatings / corrosion from the outside in and inside out.

2. Steel tanks are perfect for tension ("hoop stress"), but very sensitive to non-uniform lateral pressure, which is typical during the backfill process. Think of a soda can. Holds lots of pressure but you can crush with your hand.

3. Steel tanks are mostly design-build. Better to spec a tank than build one.

I am a steel guy, and I'm sure below grade steel tanks are still done in some corners of the world, but not a good application.

 

[JStephen]

Rectangular steel tanks are a very inefficient use of labor and materials, and so are not commonly built in very large sizes. Partially burying a steel tank creates problems rather than solving them and is not normally done. So ideally, you want circular tanks above ground.

For the actual design, there are flat-plate formulas in Roark's Formulas for Stress and Strain, among other sources.

Because tanks like this are seldom built, there's not any design standard for them or any set way of doing things.

In the actual design, you'll need to optimize material costs versus labor costs (you can use thicker plate and fewer stiffeners, or thinner plate and more stiffeners, for example) and this is one reason it's advantageous for the actual fabricator to do the detailed design.

 

[JedClampett]

Ditto what the others said. First time someone drives a truck next to it, the walls will buckle. If you need a steel tank and it needs to be underground, you should build a concrete vault to hold back the soil and put the steel tank into it. But it's super expensive and inefficient.
Try to talk whoever has this wacky idea into a round steel tank above grade or a concrete tank below grade.

 

[S275]

Does STP stands for "Sewage treatment plant"?

I think it is better to have the tank made of reinforced concrete for durability purposes.

good luck