update beam #156

[jobinhio]

• [x] Have you checked to ensure there aren't other open Pull Requests for the same change?
• [x] Have you fixed a Bug ?
• [ ] Have you added the documentation of the example or benchmark ?
• [x] Have you successfully run the example or benchmark?
• [ ] Have you documented the results?
• [ ] Have you added the images to the documentation?
• [ ] Have you added the vtkjs files for 3D visualization in the documentation?
• [ ] Have you added the vtkjs files to a Data Management Plateform e.g https://girder.math.unistra.fr

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[jobinhio]

here are the results of displacement.

here are the results of principal stresses.

here are the results of tresca criterion.

here are the results of von mises criterion.