Hello Peteroznewman,

Thank you for your reply ! Yes, I have set it to linear. Here is a “proof”:

That was also my first thought when I saw the exported stiffness matrix 😅 Here is a screenshot from solver output to verify that BEAM188 element is used. If there would be 3 nodes I think that Ansys would use automatically the BEAM189 element which is 3 node element:

I also tried with a circular cross-section in Ansys and hand calculation, but there still is big difference when comparing stiffness matrices, but displacements/deformations matches like in the above case of the rectangular cross-section. I thought if the difference comes from the calculation of the cross-section's torsional constant J and shear area As in the case of rectangular cross-section.

Best regards,

Pirkka Ruotsalainen