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Structural analysis solvers tailored for semi-analytical models

• Linear statics: [K]{u} = {f}
• Eigensolver for Linear buckling: ([K] + lambda[KG]){u} = 0
• Eigensolver for dynamics: ([K] + lambda^2[M]){u} = 0
• Nonlinear statics using Newton-Raphson
• Nonlinear statics using the Arc-Length method

Currently these solvers are pretty much compatible with my other repositories panels, buckling.

Citing this library

Saullo G. P. Castro (2026). Structural analysis solvers tailored for semi-analytical models (Version 0.4.2). Zenodo. DOI: https://doi.org/10.5281/zenodo.2581212.

Documentation

The documentation is available on: https://saullocastro.github.io/structsolve.

History

See CHANGELOG.md for the details of each version.

• version 0.4.2 (2026-09-17)
  • Fixed the eigenvalue shift of the sparse solver of lb, which could return buckling loads higher than the critical ones
  • Fixed wrong buckling loads of the sparse solver of lb when SciPy is linked against Intel MKL 2024.2.0 to 2025.0.0 (e.g. Anaconda on Windows), whose dsteqr routine breaks ARPACK
  • lb condenses out the dofs where KG is null and solves small condensed problems with a dense solver
  • lb verifies the eigenpairs of the sparse solver, raising an error instead of returning wrong results
  • The sparse solver of lb returns the load multipliers sorted as the dense solver
  • Newton-Raphson with full Newton iterations and a relative convergence criterion by default, reaching quadratic convergence with exact tangent stiffness matrices
  • Fixed the load-factor bookkeeping of Newton-Raphson, which could finish before reaching the full load
  • Arc-length methods (Riks and Crisfield) rewritten, able to trace limit points, snap-through and snap-back until a load factor of exactly 1.0
  • Sphinx documentation
• version 0.3.1 (2026-04-09)
  • Robust estimation of the eigenvalue shift for singular matrices in freq and lb, and new skip_null_cols argument
  • Python 3.14 support
  • Estimation of the eigenvalue shift in freq and lb
  • Packaging with pyproject.toml, GitHub Actions and a test suite
• version 0.2.2 (2019-03-02)
  • Release of 0.2.1 with an updated distribution
  • Fixed the dense solver of freq
  • freq returns the eigenvalues lambda**2 instead of the natural frequencies
• version 0.1.0 (2018-06-23)
  • First release, with the solvers from compmech

License

Distributed in the 3-Clause BSD license (https://raw.github.com/saullocastro/structsolve/master/LICENSE).

Contact: S.G.P.Castro@tudelft.nl