Hi,
When I use RAM Elements for a 2D analysis such as a beam or column, it says I have a local instability for Node 1 at DOF RX. If I fix the node for RX, the warning goes away. I have a couple questions regarding the boundary conditions.
1. Is RX torsion in this case?
2. In this case, since I only have 1 member, does the member hinge conditions do anything?
1. RX = rotation about the global x-axis, which is associated with beam torsion in this case.
2. The hinges do not help with torsion stability. For your model, all 6 Degrees of Freedom are considered: TX, TY, TZ, RX, RY, and RZ. With the pinned supports, there is nothing preventing the beam from spinning in torsion, which is why the instability occurs. Fixing RX at one node will eliminate the instability.