Reactions increase with the increase of meshing and element numbers

[Anonymous]

Hello everyone. I am new to Robot and I am using it for my final year project at UCL Uni in  London.

I am analysing a 32m high wall/shell to find the support reaction to see if it  matches with the hand calculations. however the reactions increase with the increase of mesh refinements. my project supervisor says the reactions need to converge at some point, but in my case they keep increasing. the only case where I get results similar to hand calculation is when the element sizes are 0.5m x 0.5m. the wall is 32m high and 1m x 4m in cross section.

I tried to  attached the robot file but this website kept rejecting it.  . Would be grateful if someone helped. 

Thank you

Ali

[Simau · Accepted solution]

Zip it before upload

[Anonymous]

I have zipped and uploaded the file 

[Simau]

Hi @Anonymous 

Your hand calculation assumes that the cross-sections stay straight, which is not the case with FE calculation.
The result of the vertical reactions is nil, but the diagram will change with the size of FEs.

[Anonymous]

Hi Simau.

Generally what element size gives reasonably accurate reactions and stresses?

I am using the student version and the smallest element size I could do is 0.1m x 0.1m.

Could you also please send me the the model that you created to see what kind of reactions you have used. 

Thank you. 

[Simau]

Hi @Anonymous 

The accuracy of the result will increases with smaller mesh. 

But it's also a balance between accuracy and calculation time. 

File here https://we.tl/t-7PYYU7KDpE

Report

[Simau]

The accuracy of the result will increases with smaller mesh. 

But it's also a balance between accuracy and calculation time. 

File here https://we.tl/t-7PYYU7KDpE