Stability Diagnostics¶

Analysis checks whether the actual supports prevent planar rigid-body motion and lists affected global DX/DY/RZ directions when they do not. Solver instability errors are translated into joint-level messages where possible. A diagonally scaled stiffness check rejects singular/numerically ill-conditioned results even when the solver returns finite values. Up to 600 free planar degrees of freedom it uses a dense spectral check. Larger models retain sparse matrices and inspect up to six near-zero modes with a shifted sparse eigensolver. This targets mechanisms in the positive-semidefinite elastic stiffness, not buckling modes. Zero-stiffness directions are detected directly, including in large models. Diagnostics show up to 24 affected node/direction labels; these are hints, not a unique identification of every defective member. Very large stiffness contrasts can cause poor conditioning without a physical mechanism. An incomplete sparse check does not certify the model: a found mechanism is reported, otherwise results are rejected with a convergence message. Nonfinite-result checks remain active. P-Delta additionally checks the actual effective stiffness used for each combination before the second-order solve. For larger systems it targets the smallest algebraic eigenvalue, since an indefinite stiffness can have modes far from zero. Nonpositive effective stiffness rejects the result; this is not a buckling load-factor calculation or a material-plastic stability assessment. Sparse factorization can still consume substantial memory for large models.

Source: GUIDE.md. This manual follows the current repository; the published rc1 wheel has a smaller feature set.