help with structural calculations.

[dalcazar]

Hey guys, I've been asked to provide structural calculations for containers that have been braced to hold water. I know that the way the system is designed works, I just need to prove that it does. I just don't have the vocabulary to look up what I need online to find the equations and I need some help with this if possible

I have a 40 foot container that has been reinforced externally with a perimetral 100x50 beam of 5mm (or 1/4 in) rectangular steel at one meter from floor level and internally braced with 20mm diameter rod under tension between the walls at the same height. The floor is held up with 2x6 C-section channel every 30 cms that span the container widthwise and a 150x50 rectangular beam of 1/4 in thick steel that spans down the middle of the container widthwise. maximum unsupported span at any point in these calculations is 2.4 meters

I know that water pressure is nowhere near the yield strength of the steel rod inside the container, so that isn't a problem.

What I need to know what equation to use in order to prove that the steel beams and channel won't buckle or bend under the weight of the water. Max water level is 2.4 meters. Can you please point me in the right direction for this?

Thanks so much.

 

[msquared48]

First of all, there is no one applicable equation here, there are several.

Second, any beam will deflect under load, any beam. And there are equations for that too. The question is how much can you tolerate?

Hate to say it, but you need to engage a structural engineer here. Sorry.

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

 

[dalcazar]

I understand that deflection WILL happen, all I need to show is that the weight of the water will not exceed a fourth of the yield strength of the beams involved.

I basically need to know what the yield strength of different cross sections and materials are for the size of these beams. I can calculate the pressures and forces involved with no problem, I just have no clue how to express the strength of the beams in relation to those forces.

 

[Ron]

Agree with Mike. If you don't understand the interactions between the structural components, how do you know when you have the right answer? You can blindly apply a simply supported beam equation for deflection or bending, but do you know if that replicates the condition you have in the structure? You could have a very simple problem or it could be relatively complex to analyze. You haven't given enough info to figure that out.

How is the keel beam supported? Is the container portable or is it permanently affixed to something? If it is stationary, how is it attached to its support? If it is lifted, where are the lugs and can it be lifted when fully loaded?

A sketch would help as well.

 

[csd72]

If there is a potential safety issue here than I would strongly advise you to get a structural engineer involved.

Personally I wouldnt dream of getting involved in a bioengineering problem, and structural engineering can be just as complicated. It is the things that the untrained eye doesnt see that will get you in the most trouble.

 

[rb1957]

yeah, the question is too complicated for a forum, there are too many things to check, the way the question is posed will have us playing "what if" or chasing our tails into blind alleys till the cows come home. and there's too much "capability gap" between the poster and the problem, judging by the way it's posted.

i figure that a volume of 300,000 lts needs a bit more care and concern

 

[csd72]

Dalcazar,

It is ethically wrong to practice outside your area of knowledge, and this is way beyond that by the looks of things. I am sure that you would be capable given enough time to study this but it is beyong your chosen area of engineering.

Also, if you are in california then this could require a seismic deign by an SE. That would then be beyond even my experience, though at least I am aware of the extent of my ignorance on that.

 

[JAE]

I agree with csd72. Get an engineer to help you with this. Very important to do so as you could be in big trouble if something goes wrong (the kind of trouble that is spelled l-a-w-s-u-i-t).

 

[rb1957]

i'd be more worried about the trouble spelt h-u-r-t/d-e-a-d p-e-o-p-l-e

so, don't get a lawyer, get an engineer

 

[csd72]

I can remember one of my university lecturers trying to imprint on us the importance of understanding the topic.

" As a doctor you generally will kill only one person at once, as an engineer you can kill thousands of people!"