Question:
During the calculation, I get an error message in RFEM with Error No. 1639, or in RSTAB with the Error No. 1640 "Member No. XY | Member hinges No. YZ are freely rotable about the x-axis. Please check this in Table 1.17 (or 1.7 in RSTAB) or another related table." How can I solve this problem?
Answer:
In fact, this error message only appears if a member hinge that allows a rotation about the local x‑axis has been assigned to a member at both ends. Thus, the member can rotate freely about its own axis and is therefore unstable.
Assign a new release to one of the member ends where the degree of freedom φx is not hinged.