Learning Forum

[yasser1987]

Dear All 

 

 i want to model a soil under  tripod bucket offshore foundation  and getting the displacement and rotation by applying  wave load , the soil should be modeled with mohr Colomb theory and it is sandy clay, but unfortunately i do not know how to do it , could you please someone help and guide me, i mean if there is any tutorial or sample project could please introduce to me   actually i do not know which steps must be followed on ansys workbench19.1 in order to simulate the soil,i?step by step approach 

 

 many thanks 

 

[peteroznewman]

Here is a discussion on Mohr-Coulomb material model.

[yasser1987]

many thanks, Peter 

but you know my problem is that i do not even know how to model it on Ansys I mean step by step to simulate the soil on ansys, for example  how to make a model !how to apply the boundary conditions and theories  ! which analysis system or costume system should be used for modeling a soil in the workbench 19.1

I am familiar with Abaqus  and but I am not familiar with ansys, do you think if there is any project or tutorial in order to learning soil modeling by ansys 

please help and guide me i got stuck in project 

[peteroznewman]

Hi Yasser,

There is a lot to learn. Do you already know a CAD system? If not, then you must start to learn SpaceClaim that comes with ANSYS.

For this model, you are interested in the sand and its ability to withstand the loads from above, so the structure above can be simply a way to transfer load to the buckets.

I assume you don't care about the stress in the bucket material and how the top of the bucket connects to the tower.  You need to draw three buckets in SpaceClaim or your own CAD system. The buckets are just simple cylindrical surfaces with a flat top, and construct solid bodies that represent the soil that is in each bucket and outside all the buckets out to a radius of 3*(S+D) and below the buckets to a depth of 3L. 

Start reviewing some tutorials on SpaceClaim in the Tutorials section of this site. 

Please provide the dimension of L, D and S and I will create a tutorial using this example.

You marked this discussion as Solved, by clicking on the Is Solution link above. That was a mistake as many people will not read discussions marked as solved because that indicates there is no need for any more help. I will help you get the geometry you need, then you can start a New Discussion for how to build the model with that geometry in Mechanical.

Regards,
Peter

[yasser1987]

Dear peter 

Hello

 

i really appreciate your response 

yes actually  i  don't care about the stress in the bucket material and top of bucket i assume is integrated with the tower, however, in reality, they are welded together 

i want to see and get the  Deformation and rotation of structure when the sea wave load is applied to the structure 

The bucket diameter is varied as 6, 9, 12, and 15 m 

skirt thickness was fixed at t=25 mm

skirt length is varied as 3,4.5,6

(S/D)critical=1.5, 2 

i also attached those pictures in order to be cleared 

Mr,Peter please help and guide me  

 

 

[peteroznewman]

Should the buckets be considered rigid or flexible?

[peteroznewman]

Here is the geometry step. I found after I imported the geometry into Mechanical that the tops of the buckets were merged (lost), so I have to copy/paste the bucket tops to get them back.

https://youtu.be/6WTd7mWIeTg

[peteroznewman]

Here is more geometry prep in part2

https://youtu.be/_TC1-QMUpXU

[yasser1987]

should be considered as a rigid body 

[peteroznewman]

Here is the model building to define contacts, loads and supports.

https://youtu.be/KIRixlkbYM4

[yasser1987]

Dear Mr,peter

 

many thanks for your help,you are amazing  

no one in my life did such this favor to me already 

i have followed your steps and tutorials up to now ,

what would be the next steps ?

 

[peteroznewman]

Part 4.

https://youtu.be/lMGv7Bq5BoM

[peteroznewman]

 Part 5.

https://youtu.be/nt-d4o1CPkk

[peteroznewman]

Part 6: Building a better mesh.

https://youtu.be/N4eNICtHrps

 

[peteroznewman]

Part 7: Results from the better mesh

https://youtu.be/lOO9N15JQUA

 

Please start a New Discussion to ask questions about your model. You can refer to this discussion by inserting a link.

You can show your appreciation by clicking Like below the posts that are helpful.

 

[yasser1987]

dear Mr Peter 

 

many many thanks for your help i have no words to express my appreciation 

 

i have problems 

first of all , when i defined the material properties in the engineering data then  i go for refreshing the project, in the model option the question mark appears  not the mark shows it's ready for solving 

but after that when i go into project i can assign the materials that i  have already defined to the buckets and the soils and then i followed your setting for the mesh and solving then click on the solve tab but i have faced with this error 

 

 

please guide me 

[peteroznewman]

Please follow the directions for creating a Workbench Project Archive .wbpz file. Then attach that file to your reply. I can look in that file to see what is wrong. Note that the file must be less than 120 MB to attach. You might need to RMB on Model and Clear Generate Data to reduce file size.

[yasser1987]

Alright 

[peteroznewman]

Hello Yasser,

Sorry for the delay in replying.

I downloaded the archive you saved in the previous post. You seem to have overcome the problem in the post that had the ? in the Model item. This model actually started solving.

If you click on Solution Information, you will see a long text file of the solver output.  One of the messages is this:

 *** WARNING ***                         CP =      14.125   TIME= 8:28
 The material solution failed for element 6063 with material 11.         

 *** WARNING ***                         CP =      14.125   TIME= 8:28
 The material solution failed for element 6069 with material 11.         

This means that the displacements that went into the mohr-coulomb material model did not compute a valid output. This often happens with Geomechanical materials like mohr-coulomb. All my examples in the model building videos used simple linear elastic materials.

Here is an illuminating discussion where a member was trying to compute stresses in a mine shaft. As soon as the mohr-coulomb material model was added, an error occurred. It was because the model boundary conditions (Fixed Supports) generated tensile stresses that the mohr-coulomb material model couldn't handle. As soon as better boundary conditions were applied, the model solved because there were no longer spurious tensile stresses.

A second discussion on mohr-coulomb.

A third discussion on mohr-coulomb.

I recommend you make a very simple model of some soil and a wall, as simple as you can think of, and use that model to see how to get the mohr-coulomb material model to solve. Maybe a rectangular block of soil in a rectangular bucket. Move one wall of the bucket in or out and see what happens.

Let's close this discussion, as it was a good example of how to do everything except the soil. Please create a New Discussion to ask questions about this new simple model that uses mohr-coulomb, because this discussion is already marked as solved.

Regards,
Peter

[yasser1987]

Dear peter 

 

Many thanks for being a considerate and helpful person,

unfortunately, it is not solved yet,

i want to ask you if you run it without any problem ???

because when i start to run( exactly the file I upload for you), i am facing with this error and stops, i do not what to do i checked again all parameters but did not work 

 

could you please if is possible to share the model that you made with me? in order to get rid of the error  

sorry if i bother you with asking many questions since  my project got  stopped for 4days and running late for its deadline 

furthermore, if you agree i will create new discussion after solving the error  otherwise I'll create a new topic 

 

 

Best regards

Yasser

 

[peteroznewman]

Dear Yasser,

If you take the model you attached above, and scroll up in the Solution Output, you will see the warning messages I showed you about the material.

If you open that model and in Engineering Data, delete the Mohr-Coulomb model from the soil, Refresh the Project and Solve the model, it will solve without error. That archive is attached.

That is why you need to take some time to understand the Mohr-Coulomb material model and ask questions in a New Discussion.

Regards,
Peter