Great Shear forces in foundations model

[sedefass]

Hi there, I made a model for a foundation under X bracing, in which the uplift is turned on. The results of all forces were expectable except the concentrating of Qxx and Qyy (what can I do about it). 

Then I made another model with frame elements, the the results became unintelligible.

Please see the both models and tell me if I got something wrong in both of them.

Now I see that the file is to large (it is 22MB). What should I do to send it to you?

Thank you in advance!

[Artur.Kosakowski]

http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Sending-bigger-files/td-p/3795062

[sedefass]

http://www.4shared.com/zip/ZUkbqy4q/Great_Shear.html?

[Artur.Kosakowski]

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Hi there, I made a model for a foundation under X bracing, in which the uplift is turned on. The results of all forces were expectable except the concentrating of Qxx and Qyy (what can I do about it). 

Then I made another model with frame elements, the the results became unintelligible.

Please see the both models and tell me if I got something wrong in both of them.

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I'm sorry but I'm not sure if I understand what you mean writing: the results became unintelligible.

Could you make some screen captures and indicate which results and where in the model to look at and what results you expect please?

[sedefass]

Hi, Artur,

Forgive me if I didn’t expose the problem clear enough.

Here is the screen shots of the results that trouble me.

I guess that concentrating of Qxx in the corner is normal for FEM analysis, but the other one with that over 100 000 kN Fz force is beyond all my expectations.

[Artur.Kosakowski · Accepted solution]

For the shell model I think that we have combination of two effects. Firstly the slab is sort of 'broken' in this point (you can see that the deformation 'straps' are of different widths and then in such points as corners the results for surface elements are supposed to have larger values (the larger the smaller elements are). This is similar to the values of bending moments over the point support.

For the other model I think that you should consider modeling the soil in the different way. What happens is that you have continuously supported bars (elastic soil) but the connection with the walls are done in points which causes strange looking shear force diagram (as if you have a number of separate beams from node to node of the meshes). Personally I would replace the elastic soil with unidirectional elastic supports defined in the nodes at the bottom edges of the walls.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[sedefass]

Thank you very much for your reply and please exuse my delayed post!