Mechanical Painfully Slow Because of Too Many Springs

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  • Last Post 29 March 2019
mobiusprime posted this 25 March 2019

Hi ANSYS Community,

 

I'm quite new to ANSYS, have been using it for a couple of months now, and searched for several times for a similar topic and wasn't able to find anything related to the specific issue.

I'm modelling an electrical transmission line tower and its foundations considering the soil structure interaction (SSI) using Winkler Model (Spring Model) for the soil. In the regard for the Winkler Model i have found very helpful guidance in topics throughout the community and i am very thankful for that.

The problem is, i'm modelling a tower that's quite big and so are its pile foundations. The foundations comprise of 176 piles with depths that vary from 25 meters for the pile caps and 20 meters for the ground beams. Since I have to insert a spring every half meter of the pile for the Winkler model and that gives me a total of 16960 springs and I'm attaching every single spring directly to the respective mesh node of the pile in that specific depth (I haven't been able to find an easier way of doing it) it has been very annoying to do so, and that's not even the worst part. As I insert more and more springs it becomes more and more slow to edit things in the Outline, I tried to do everything to improve Workbench's performance but had not been able to do so. ANSYS isn't consuming all the RAM, or disk, or even the processor, i can manipulate the geometry quite quickly, Mechanical solves the model quite quickly also, the only problem that i have is that when i edit the Outline it takes like forever, it takes like minutes to add a new spring or to add anything to the model and given the number of springs to be added I'm starting to doubt that I'm going to be able to finish it in time for my presentation.

If anyone knows an easier way to do this, or some way of improving Workbench's performance i will be very much thankful. Any help is valid!

Just for information: the springs stiffness vary with depth and all the springs in the same depth have the same stiffness for all the piles. I haven't been able to find a way to define A body to ground spring and its direction (i need to apply 2 springs per node, one in the X and another in the Y direction) and applying it to multiple nodes, that would solve the problem but i don't even know if that's possible so right now i'm defini reference and mobile points for every single spring.

Sorry if the text is a little confuse, but english is not my first language. And thanks in advance for any help i mght get.

 

 

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sk_cheah posted this 26 March 2019

It sounds like you're pushing the limits of the GUI outline tree. As your model is linear (linear springs), you could potentially look into using superelements. An example is to create a superelement for one 'pile' and duplicated (SETRAN) for 176 piles. I am not sure "condensed geometry" in Mechanical could do the job but it is possible in Ansys Classic though painstaking if you're not familiar with it. 

Good luck,
Jason

Aliyu posted this 28 March 2019

Hi Mobiusprime, Your question is the closest that i found to mine in a while. I am also trying to model soil-pile interaction using winkles springs but haven't found any help to rely on. Could you kindly help me with the procedures as I am very new to the use of ansys workbench. Please kindly assist as I await your response.

Regards, Aliyu

mobiusprime posted this 28 March 2019

Hi Aliyu,

 

First of all i would like to thank sk_cheah for the help, I haven't been able to try the solution he suggested yet, but i very much appreciate the help.

Aliyu, you can insert a spring in the connection section of the outline tree, and then you can define the mobile and the reference of the spring, then you select the "body to ground" option and define the reference (where the spring begins) and the the mobile (where it will be attached) in such way that the spring assumes the direction in which you want it to be. In my case, since i want a spring every half meter i meshed the pileswith an elmente very half meter and attaches the the springs to the mesh no in evry single depth of the pile.

I hope that helps! Any doubt you just say.

 

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Aliyu posted this 28 March 2019

Hi Mobiusprime,

Thanks so much for your quick response, you have no idea how relieved this has made me. Thanks again. I still have some questions though, if I may: 1. Most literature I have seen assume the pile as a beam element and as such only apply a horizontal single spring(p-y) to a level. I however assume that in 3-D this should be applied to every node on a level along with the vertical springs representing t-z (I'd like your opinion please). 2. How do I input the p-y, t-z and q-z values in workbench?

I'm sorry these seem like a lot of questions but I'm afraid they have been bothering me for sometime now and I'm glad to find that someone shares my concerns.

Thanks so much sir/ma

Aliyu posted this 29 March 2019

Hi ANSYS Community, Thanks to Mobiusprime, I have progressed a bit in the understanding of spring attachments to simulate foundation stiffness but would kindly appreciate any further help with the questions below: 1. Most literature I have seen assume the pile as a beam element and as such only apply a horizontal single spring(p-y) to a level. I however assume that in 3-D this should be applied to every node on the circumference of a chosen ground level along with the vertical springs representing t-z (I'd like your opinion please). 2. How do I input the p-y, t-z and q-z values in workbench? Any useful materials or even screenshots would help greatly.

I'm sorry these seem like a lot of questions but I'm afraid they have been bothering me for sometime now and I'm glad to find that this community can help.

Thanks, everyone.

Aliyu

Aliyu posted this 29 March 2019

Dear Mobiusprime and s_k cheah,

I have carefully gone through the questions and comments on here and found you two to be the closest to providing the answers I seek, given your proficiency in the use of ANSYS Workbench as it relates to my problem.

This platform has no provision for direct messaging, hence I can't reach you and may not be so lucky to be online at the same time as you.

Could you please kindly reach out to me on a.abdullahi@surrey.ac.uk?

 

warm regards,

Aliyu

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