Nodal reaction force for nodes with zero prescribed displacement vs fixed

[danasolav]

Hello,

I am confused about the behaviour of the outputted nodal reaction forces when I fix the nodes vs when I prescribe zero displacement in all directions. The results should be equivalent, and they are for displacements and stresses, however in the former case I'm getting zero reaction forces on the fixed nodes and in the latter they're non-zero (which is what I expect it to be in both cases). Why is it different?

Thanks!

[brandonz]

Hi,

When you fix the nodes you actually completely remove those degrees of freedom from the problem, which is why there are no reaction forces (it looks like you are getting zero reaction forces, but in reality you're just getting nothing). When you prescribe zero displacement, the degrees of freedom remain but just have their value set to zero. In this case the reaction forces can be calculated.

Hope this helps!

Brandon

[danasolav]

Thank you for the answer, Brandon!