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Post by alfonsogdr » Fri Feb 19, 2021 6:29 am

Good Afternoon to all OpenSEES community.

I have a question related with ShellDKGT element.

I have done several tests comparing ShellMITC4 and ShellDKGT elements using LayeredShell sections with J2Plasticity material and I have similar results in Displacements Field and Tension Fields. The problem appears with strains.

In this message I am going to show an example of a model with an IPE beam embeded at one end with a momentum and a vertical load applied at its free end.

I have modeled the same model using ShellMITC4 elements and ShellDKGT elements and I obtain similar results for displacements and tension.

Picture_2 and Picture_3 show the results of von mises tension and equivalent strain for gauss point 2 of layer 3 for all the elements in the model using ShellDKGT elements. (I have used the command "recorder Element -file filename.out -time -ele eletag material 2 fiber 3 stress/strain" in order to get tensions (sigma11, sigma22, sigma12) and strains (eps11, eps22, gamma12) and then I have used von mises stress equation and von mises equivalent strain equation showed in in order to obtain these values for each gauss point).


In Picture_4 the results of stress/strain for some elements that have higher stress are shown. Looking at the picture, it can be seen that the tension values vary uniformly, with adjacent elements having similar tension values while the value of strains alternates in an inconsistent way (goes up and down). Even for elements with similar stress values, the strains values corresponding to these elements are very different from each other. This behaviour not only happens for this gauss point and this layer of these elements. It occurs for all gauss points in all layers for several elements of the model and for direct strains values too (eps11, eps22 and gamma12). I also have this problem in other models that I have done comparing ShellMITC4 and ShellDKGT but only with strain values.


I wanted to know if this situation has happened to another user or if there may be a problem when obtaining the deformations in the ShellDKGT element

Thank you very much for your time and sorry for the inconveniences. Regards.

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