Foundation elasticity

[mdadela]

Hi,

I have modelled a concrete tank on elastic soil by defying elastic planar support. Then I wanted to see the reaction map so I defined foundation elasticity to get it. But I have noticed all the results have been changed.

My question is: Can we use both methods simultaneously? I mean can we define elastic support and foundation elasticity at one time?

And:

Which way of modelling elastic support is better? (Because the results are different)

Please find my file attached.

Regards

Marek

[stm1A]

HI,

I usually define an elastic paramiter k for ground slab,

than see results of ground earth tension with maps results for "soil reaction K".

i would link central pillar directly on slab.

[Artur.Kosakowski · Accepted solution]

My question is: Can we use both methods simultaneously? I mean can we define elastic support and foundation elasticity at one time?

No, as in this way you define boundary conditions two times (they add up). 

Which way of modelling elastic support is better? (Because the results are different)

For the same values the results should be the same (or similar as for the surface supports the tricky part are the nodes on the common edges between panels especially when different KZ are assigned) however if you want to see the map you should use the elastic soil. 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[mdadela]

Hi Artur,

You said: 'For the same values the results should be the same'. I have just done a quick check in a file as attached and the results are significantly difeerent. For instance see the bending moments in a base slab in attached PDF.

Marek

[Artur.Kosakowski]

Let's simplify this. Could you create a model with the bottom slabs only defined side by side and with both types of boundary conditions please? If the results are different attach it. Thank you. 

[mdadela]

Thank you, Artur, for your attention, I believe this simplified model you mentioned would work, but what about more complex situation, as in my tank case? I am interested in this particular model and still I don't know which way of defining elastic soil is more adequate. 

Marek

[stm1A]

hi 

if you want to see the map you should use the elastic soil.

just a question about your model:

how can you create new windows with some panel only? like windows with top slab, windows with walls...

thank you

[Artur.Kosakowski]

Personally as stm1A I'd use elastic soil in the definition of panel's thickness. 

Going back to the surface elastic supports mind not to mark this check box:

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Artur.Kosakowski]

For the model you attached:

[mdadela]

Pick a panel and then use this button:

[mdadela]

Actually I didn't realize the importance of the "constant elastic coef. at support nodes". And I could not find the explanation in the help files. Could you tell me the exact purpose of this tick. Does it mean that in every single node the coefficient is the same, otherwise the coefficient is calculated in relation to the size of the finite element? Is that right?

Marek

[Artur.Kosakowski · Accepted solution]

Correct.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[mdadela]

Thank you very much, Artur.

[dineshvekariya123]

SLAB