https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-and-no-convergence-of-nonlinear-problem/m-p/13726578#M85081 <P>no need to assign those diagonals as tension only bars. Change them back to regular bars and the model will converge with no instabilities</P> <P>Another option is to keep those diagonals as truss bars ,but resisting tension and compression . But also change the releases pinned-fixed and fixed-pinned to be blocked on the RX direction(torsion&nbsp; ,because this is causing the instability type 2 which cannot be ignored</P> Wed, 16 Jul 2025 02:06:49 GMT Rafacascudo 2025-07-16T02:06:49Z https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-and-no-convergence-of-nonlinear-problem/m-p/13726480#M85078 <P>Hi, I have a model of a tower frame with tension only web members and stay cables.&nbsp; I am receiving error messages of no convergence of a nonlinear problem and I have instability in two nodes I cannot troubleshoot.</P><P>&nbsp;</P><P>Please help!&nbsp; My model is attached, thank you!</P> Tue, 15 Jul 2025 23:00:56 GMT https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-and-no-convergence-of-nonlinear-problem/m-p/13726480#M85078 hogerc 2025-07-15T23:00:56Z https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-and-no-convergence-of-nonlinear-problem/m-p/13726499#M85079 <P>Zip it before attaching&nbsp;</P> Tue, 15 Jul 2025 23:33:26 GMT https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-and-no-convergence-of-nonlinear-problem/m-p/13726499#M85079 Rafacascudo 2025-07-15T23:33:26Z https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-and-no-convergence-of-nonlinear-problem/m-p/13726507#M85080 <P>Thanks for looking at this, please see zip file attached.</P> Tue, 15 Jul 2025 23:50:39 GMT https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-and-no-convergence-of-nonlinear-problem/m-p/13726507#M85080 hogerc 2025-07-15T23:50:39Z https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-and-no-convergence-of-nonlinear-problem/m-p/13726578#M85081 <P>no need to assign those diagonals as tension only bars. Change them back to regular bars and the model will converge with no instabilities</P> <P>Another option is to keep those diagonals as truss bars ,but resisting tension and compression . But also change the releases pinned-fixed and fixed-pinned to be blocked on the RX direction(torsion&nbsp; ,because this is causing the instability type 2 which cannot be ignored</P> Wed, 16 Jul 2025 02:06:49 GMT https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-and-no-convergence-of-nonlinear-problem/m-p/13726578#M85081 Rafacascudo 2025-07-16T02:06:49Z