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Uniform moment in ABAQUS

Hello everyone,

I am modelling a rectangular cross section beam in Abaqus using shell elements (S4R) in order to study its lateral and torsional deformation. I am trying to apply a uniform moment (Mo) to the beam by applying compressive forces in all the end nodes avobe the neutral axis and tensile forces in the end nodes below the neutral axis. I can tell this is not working because the Abaqus results for vertical displacement do not match with the analytical results of the next equation: y''=Mo/EI

Could you please tell me if there is any other way to represent a uniform moment or how can I improve what I am doing?

Thank you very much for your help

Shell elements have rotational degrees of freedom, so you can apply a moment directly to nodes if you want. Another options is to place a reference point at the neutral axis and kinematically couple that to the end edge. Then you can apply the moment to the RP and it will apply the moment to the entire end section. This has the downfall of overstifffening the end region, so don't trust stress values right next to the coupled nodes.

Thank you so much for your answer, it was very helpful. I have been checking my model and I noticed that the vertical displacement values vary depending on where I put the supports along the web of the beam (simply supported beam with 12 rows of shell elements) Do you know where I should place the supports, would it be right to make the lower nodes pinned?

Thank you again and regards

I am not sure I followed the details of your model. I would probably need some pictures to understand what you're describing. However, if you're just looking for a pure moment on a beam you could setup a 4-point bend test (Google it for images). The region between the two center supports will have a pure moment (no shear) and there are analytical equations to compare against.

Thank you very much for your time. I solved my problem and the analytical results now match.

Kind regards.

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