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[Hugo Bell]

Hi, 

I'm a postgarduate student completing a dissertation on shell concrete elements attempting to analyse the structure below however the result is cleary wrong, any advice?

[Sahil Sura]

Hello Hugo Bell,
Looking at the provided details, I can help on addressing the issue you’re facing.

The material used Glass Reinforced Concrete is a highly non-linear material, whose non-linearities should be appropriately accounted for in the given example. It would be also necessary to account for the other non-linearities like the geometrical and the contact if present. Verifying if the material is completely defined to capture the required behaviors is also important, Material Designer is one of the best resources to opt for when accounting for the behavior of composite materials. (Introduction to ANSYS Material Designer - YouTube)

Mesh plays a critical role in attaining the solution for an FEA problem, thus coming up with a good mesh can be one suggestion to help converge the problem. Considering this as a surface body, face sizing, or edge sizing and appropriate methods from the Mesh tab would help you solve the model.

For any complex non-linear problem, timesteps/ substeps play a critical role. Thus increasing the number of substeps or reducing the timesteps would help in resolving the issue. Converting the problem into a multistep problem would also be helpful if you’re loading it in steps.
There won’t be a perfect equation to define the number of substeps or timesteps exactly, thus they can be appropriately defined by looking the convergence behaviors of the solution, which can be accessed via the ‘Solution Information

Last but not least, ensuring proper boundary conditions and contact behavior is something that shouldn’t be ignored.

Please find the following references which might help you -
Chapter 26: Nonlinear Analysis of a Rubber Boot Seal (ansys.com)
Step Controls for Static and Transient Analyses (ansys.com), Steps, Substeps, and Equilibrium Iterations (ansys.com)
Nonlinear Controls for Steady-State, Static, and Transient Analyses (ansys.com)

Hope this helps!

Thanks,

Sahil

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[Hugo Bell]

Thank you, any further detailing on boundary conditions and contact behaviour, unsure on the direction to look into here?

 

[Sahil Sura]

 

Hi Hugo,

So ensuring the material model is right as per your criteria, for boundary conditions you can check the loads are properly scoped and there won’t be any rigid body motion due to insufficient supports. 
Checking the contacts, if they capture the required behavior.
A check on the boundary conditions and contacts for a complex assembly can be done by performing a simple Modal Analysis. So if rigid body modes are present, this will indicate an unconstrained model.

If the defined analysis runs perfectly, but you're facing this element distortion or so error, you can go for updating the Substeps/timesteps and other options from the Analysis Settings. 

Please find the following resources for further detailing on boundary conditions and contact behavior-
Stress Analysis in Ansys Mechanical | Ansys Courses

Contact (ansys.com)

 

Hope this helps!

Thanks,

Sahil

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