# FESA

FESA is a C++17 finite element structural analysis solver project. The first milestone is a reference-verified linear static MITC4 shell solver with an Abaqus-compatible input subset, HDF5-oriented results, and explicit numerical conventions.

## Current Phase 1 Direction
- MITC4 shell element baseline formulation.
- Linear elastic material.
- Nodal loads and fixed boundary conditions.
- Abaqus input subset with `S4` mapped to FESA `MITC4`.
- `S4R` deferred.
- 6 shell DOFs per node: `UX`, `UY`, `UZ`, `RX`, `RY`, `RZ`.
- Small artificial drilling stiffness.
- Constrained DOF elimination.
- Full-vector reaction recovery.
- `double` precision and int64 ids/indices/equation numbering.
- Stored-reference comparison from `references/*.inp` and `references/*_displacements.csv` without requiring local Abaqus execution.

## Reference Artifacts
Stored Abaqus examples live under [references](references).

The initial accepted artifact pair is:
- [quad_01.inp](references/quad_01.inp)
- [quad_01_displacements.csv](references/quad_01_displacements.csv)

Reference CSV displacement columns use Abaqus labels `Node Label`, `U-U1`, `U-U2`, `U-U3`, `UR-UR1`, `UR-UR2`, `UR-UR3`, mapped to FESA `UX`, `UY`, `UZ`, `RX`, `RY`, `RZ`.

## Documentation Entry Point
Start with [docs/README.md](docs/README.md).

The core project documents are:
- [AGENTS.md](AGENTS.md)
- [docs/HARNESS_ENGINEERING.md](docs/HARNESS_ENGINEERING.md)
- [docs/PRD.md](docs/PRD.md)
- [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md)
- [docs/ADR.md](docs/ADR.md)
- [docs/NUMERICAL_CONVENTIONS.md](docs/NUMERICAL_CONVENTIONS.md)
- [docs/ABAQUS_INPUT_SUBSET.md](docs/ABAQUS_INPUT_SUBSET.md)
- [docs/VERIFICATION_PLAN.md](docs/VERIFICATION_PLAN.md)
- [docs/RESULTS_SCHEMA.md](docs/RESULTS_SCHEMA.md)
- [docs/MITC4_FORMULATION.md](docs/MITC4_FORMULATION.md)

## Validation
The default repository validation command is:

```bash
python scripts/validate_workspace.py
```

At this planning stage, validation may report that no concrete build/lint/test commands are configured.