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Valued Contributor
TSOFA
Posts: 63
Registered: ‎09-22-2013
Accepted Solution

TANK FOUNDATION

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12-19-2013 02:10 AM

Hi,

 

I have a new project to design a tank foundation. The layout will be similar to the one that I am attaching. I would like to know the following:

  1. Does Robot Millennium models these kind of structures?
  2. If it does, which elements should I use (i.e. shells)?
  3. Can Robot Millennium design the foundation according to EC8 and EC2?

Thank you in advance,

Sofia

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Product Support
Rafal.Gaweda
Posts: 4,935
Registered: ‎04-26-2010

Re: TANK FOUNDATION

12-20-2013 08:15 AM in reply to: TSOFA
  1. Does Robot Millennium models these kind of structures?
  2. If it does, which elements should I use (i.e. shells)?

As shells.

 

Can Robot Millennium design the foundation according to EC8 and EC2?

 

It can calculate reinforcement for plate and shells. You have to calcaulate is as a slab \ panel(s) on soil specifying correct kz value



Rafal Gaweda
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Distinguished Contributor
bjur
Posts: 140
Registered: ‎09-14-2011

Re: TANK FOUNDATION

12-20-2013 09:11 AM in reply to: TSOFA

As mentioned earlier, use panels to model the tank.  Robot will then mesh the panels into shell elements for you.  Depending on how the tank attaches to the foundation, I would model the tank seperately from the foundation.  You can then save a copy of the model, create the foundation, eelete the tank, and copy the reactions from the previous tank design to your foundation model as loads.  This can speed up calculation time as Robot won't have to analyze the tank each time.  There are macros on this forum that help transfer loads from one model to the other.  See attached example.  This is an example of a tank that sits on the foundation but only has anchor bolts for uplift resistance.  You will see compression only springs at the base of the tank and regular springs (representing the anchor bolts) at the bolt locations.  The reactions are transfered to a foundation only model which runs much faster than when both are together.

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Valued Contributor
TSOFA
Posts: 63
Registered: ‎09-22-2013

Re: TANK FOUNDATION

12-23-2013 03:52 AM in reply to: bjur
Thanks a lot for your answer. Is it possible to send me the rtd files in 2010 version because I can't open them? I am a little bit confused of the way that "shell" elements are created compared to the "plate" elements. The only way that I know is to go to Shell structures module -> create contour -> create thickness of FE -> apply a panel with the FE thickness that is already created to contour. Is this right? If it is, what is the difference between the creation of a plate?
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Valued Contributor
TSOFA
Posts: 63
Registered: ‎09-22-2013

Re: TANK FOUNDATION

01-06-2014 11:03 AM in reply to: TSOFA

I modeled the foundation of tank using shell elements, but when I tried to analyse it the software could not find solution due to no convergence of iteration. Is something that I can try to overcome this problem?

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Valued Contributor
TSOFA
Posts: 63
Registered: ‎09-22-2013

Re: TANK FOUNDATION

01-06-2014 11:13 AM in reply to: TSOFA

the message of analysis is the following:

 

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Contributor
rigid_joint
Posts: 14
Registered: ‎03-15-2012

Re: TANK FOUNDATION

01-06-2014 02:10 PM in reply to: TSOFA

TSOFA wrote:

Is something that I can try to overcome this problem?

 


You have set up a nonlinear problem (elastic foundation/uplift) and your combinations are linear.
You have to set up nonlinear cases/combinations too and try to manipulate the non linear parameters.


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Product Support
Rafal.Gaweda
Posts: 4,935
Registered: ‎04-26-2010

Re: TANK FOUNDATION

01-07-2014 05:14 AM in reply to: TSOFA

Sofia,

 

Are you sure the base plate should be 0.01 cm thick?

Are you sure the pipes and upper plate should deflect 113 cm under selfweight?

 

Effect on bottom plate - "peaks" of 113 cm for sw

tsofa.jpg

 

With 10cm base plate sw case converges smoothly



Rafal Gaweda
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Valued Contributor
TSOFA
Posts: 63
Registered: ‎09-22-2013

Re: TANK FOUNDATION

01-07-2014 06:16 AM in reply to: TSOFA

Please find attached a dwg that explains my modeling. What I did is to use this 0.01 "film" plate in order to give the subgrade modulus properties under the 60cm and 200cm shells that are forming the foundation. I did this to take into accound the right level of horizontal forces application points and also the level of the base of foundation. 

In order to overcome the problem of converges, I changed the Kz properties of Film plates from Uz+ to none. I also applied a 30% of Kz as horizontal subgrade values. The result was to overcome the problem of analysis, but the results don't seem right. If you check the vertical displacements of the "film" panels, all the displacements are concetrated at the edge nodes and not uniformly to all the panel. The center of the panels have zero displacement or even possitive. I also tried to take out the Kz from the panels and put spring supports to all base nodes. The problem remains the same. Why? Do you think that if I change the film plate's thickness from 0.01cm to 10 cm will have the right result?

 

 

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Product Support
Rafal.Gaweda
Posts: 4,935
Registered: ‎04-26-2010

Re: TANK FOUNDATION

01-07-2014 06:41 AM in reply to: TSOFA

So every pairs of slab node and film node should be connected by this pipe bar or rigid links

 

example:

 

filmrl.jpg

 



Rafal Gaweda
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