Three supports are placed on a small model: a full anchor at node 0, a translational spring of 250.0 N/m in Y at node 1, and an imposed rotation of 0.015 rad about Z at node 2. How many freedoms become rigidly restrained? Does the spring stay a spring, rather than being treated as a rigid restraint?

1.Inputs.

Illustrative values, taken from no standard and chosen so the arithmetic can be followed by hand. Most do not describe a real pipe; read them in any consistent set of units.

2.Method.

The anchor holds all six freedoms at its node. The imposed rotation fixes one more freedom at a known value. The spring resists movement elastically and does not join the list of rigid restraints.

3.Results.

The tests check that:

• Boundary preparation completes without blocking.
• Seven freedoms are rigidly restrained.
• Exactly one spring is recorded, with a stiffness of 250.0 N/m.
• Exactly one imposed displacement is recorded, with a value of 0.015 rad.

What it shows. Checks the loads or boundary conditions prepared for the solver against a hand calculation. No system is solved.

Path exercised. The benchmark calls the solver’s components directly: elements, loads, frame solver and stress recovery. It does not go through the program’s own model-to-solve path.

Agreement. Each computed value must match the reference within an absolute difference of 1.0 × 10⁻⁹ in the case’s own units; counts and structural outcomes must match exactly. Long values are shown here to seven significant figures; the tests compare the full values in the record.

4.Run it yourself.

cd projects/chirality-piping
cargo test --manifest-path validation/benchmarks/mechanics/Cargo.toml support_boundary_fixture_prepares_mixed_supports

Hand calculation: validation/hand_calcs/mechanics/support_boundary_mixed.md. Test record, with the recorded run of 2026-07-10: mech-support-boundary-mixed.md.