Bottom Plate-Stiffened by Beams

Some questions:

Is this a new or used tank?

Dear phoenix911,

This is a new Tank.

Regards

ASD23789

My advice is that the beams should be designed by an engineer who is on site and can see the tank.

It is difficult to design such a system by using one's imagination.

Dear Lyn Sir,

This tank is to be manufactured in a shop.

Regards

ASD23789

The point that lyn was trying to make,

As an example:

you use a statement such as beams made from plate..........ok.

What is the geometry of the beams?

So, will the shop be paid to produce this tank?

If so, then the shop should do the design work. Or hire a designer to perform the work.

Where will the money go that should have been allocated for the design of the tank? Profit?

I am opposed to performing free design work for someone who will be paid for using the design I produce.

Good luck with your tank.

Without a set of plans sitting in front of me I wouldn't even hazard a single opinion or advice regarding the design and fabrication of this tank. Details details details! We need specifics, as in graphics with dimensions....

What liquid is it going to hold? Knowing this will determine the applied loads.

Is this tank being designed and fabricated pursuant to any acceptable governing standards?

Find yourself an experienced design engineer who knows what the heck he/she is doing in regard to tank structural design.

Dear all,

(The beams are I section made from welding plates together)_

can we propose to use method adopted by Brownell and young in their Roof structure design in Process equipment design book?

OR

Do we have to consider the beams as present on elastic foundation?

OR

To design the web of the beam against buckling? to consider uniformly distributed line load on such a beam?

above attached sketch of the beam arrangement.

Regards

ASD23789

Looks fine to me.

Suggestion:

Don't mix Stainless Steel plates with Mild Steel plates - and by welding!!

My opinion is that such a design will leak in:1-2 years of use...(depends also on fluid contained) - but seriously taken-see Electro Voltaic difference between this 2 materials

Secondly:

For design point of view: isn't it better to weld a thicker Stainless Steel plate instead

-by forming a cup with edges thick as the designed walls? (so much work will be saved !! and avoiding unnecesary painting..)

And concluding;

You have to design by allowing elastic movement - and not stiffening. Your design has to consider thermal expansion too - and your design is far from it (even in day-night

temperature differences)

Would be happy to hear your solution

IMHO, That is only an opinion in.

http://www.muel.com/

I could be wrong and I would be interested in your background.

I think you're all wet (pun intended) about welding mild steel and carbon steel together and having it leak within 1-2 years.

I have joints of MS and SS that I welded with MS wire over 5 years ago, that are exposed to the elements every day. They look the same today as the day they were welded. In this case I might use a more appropriate filler metal, but I see no problem welding the two together.

The OP hasn't bothered to share with us the types of steels he is using, so how can you say that thermal expansion will be a problem?

Just my 2 cents worth.

I concurr,

Mueller has been building silos like that for a long time.

Well leaving near the sea - similar silos,corroded after 2 years....

Significantly choice of material is my main subject and it is hard to expect good results

with these assumed partially conditions...

Like the others, I won't do free work and there is a lot of missing information.

One thing, don't try to consider the two plate as composite unless you have a good way to design the welds that would make them act as one.

Dear Sir,

Yes I completely agree with you sir.

We are drilling holes in MS bottom plate at successive radii and fillet welding the MS bottom plate (in the hole) to SS bottom plate.

This is in addition to the periphery welding of MS botom plate to SS bottom plate.

Regards

ASD23789

You're not supplying enough detail....I can't read the drawing, it's too small...I think all these details are pointed out in the code....try some software...

Thanks

With so much specific information being such convenient numbers (a relative density to water of exactly 1.2), I suspect and hope that this is a scholastic homework assignment. What convinces me that this is homework is the lack of critical real world information that appears to be missing to me, and I'm an electrical engineer. Will these beams be I beams, box girder beams, concrete with internal steel rebar, not to mention what will be the maximum permitted floor pressure and deflection be for static and dynamic conditions.

I now see that the OP is proposing to hand fabricate some I beams out of plate and some welding technique. I take my earlier comment back about this being scholastic homework. This seems more like a cobbled job on a fishing trawler to support a salt water hold tank of bait or catch.

As others here have said, your "best" most reliable option is to actually hire an engineer to do an analysis of your site and loads to prevent this massive over 140 tonne combination of tank and water from ripping things a part. If this is not a scholastic assignment but something that must be done without a certified structural engineer's guidance then plan on failure happening. If you are very clever you maybe able to plan your failures to be educational instead of catastrophic.

since we are assuming, my vote/guess would be its the bottom of a silo.

For your max. tank capacity of approx. 123 tons, the design of structure seems un-sufficient. You have to get it checked through some professional.

In all of the discussion above, I believe that everyone is missing the major issue; a web crippling (local web buckling) of the support beams.

I believe that the OP is green, but has come up against a problem for which he has no background. A web crippling evaluation is typically encountered as a more subtle topic in the education of a structural engineer.

(Again, I strongly suspect that an MBA was involved in the assignment of this analysis task to the tank newbie) (see www.bgstructuralengineering.com )

A couple of things to consider:

1) If you can evauate the support beam with the deepest web and prove that web crippling is not an issue, you are done.

2) Based on your picture, I now understand that the tank has an inclined bottom, and slopes to a nozzle. My experience with such tanks, in the pulp and paper industry, was that the tank under-bottom was filled with structural grout; thus eliminating the web crippling concerns ! Grouting would be possible on the tank that you describe, but grout distribution vents and grout supply pipes must be added.

OP: Be Respectful......Tell us more about your final design and how well the tank performs when installed

I would not calculate it considering each section betrween beams as a simply supported flat plate. I would look at the entire plate as a grillage, and assume the concrete base can be considered an infinitely stiff foundation, unless you are installing on soft ground.

In a brief google search I can't find the design formulae, and my text book (Theory of Plates and Shells by Wilkey)with them is buried in storage somewhere. But if you look around you will find them.

Dear All,

in earlier projects we have used the above arrangement and it is still working after 10 years.

Also as suggested by MJCRONIN, we have studied web criplling also. the provided thk are suffisient.

Thanks all for your suggestion.

Regards

asd23879