김경종
98 lines
3.4 KiB
Markdown
98 lines
3.4 KiB
Markdown
# Step 8: global-transform-recovery
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## Read These Files First
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Read the following files before editing:
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- `/AGENTS.md`
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- `/docs/ARCHITECTURE.md`
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- `/docs/ADR.md`
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- `/docs/formulations/euler-beam-3d-formulation.md`
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- `/docs/numerical-reviews/euler-beam-3d-review.md`
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- `/docs/implementation-plans/euler-beam-3d-implementation-plan.md`
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- `/src/fesa/elements/euler_beam_3d.hpp`
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- `/src/fesa/elements/euler_beam_3d.cpp`
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- `/tests/unit/euler_beam_3d_local_stiffness_test.cpp`
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## Task
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Use TDD to add local/global transformation and global end-force recovery to the 3D Euler-Bernoulli beam kernel.
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Extend the API in `/src/fesa/elements/euler_beam_3d.hpp`:
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```cpp
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using Vector3 = std::array<double, 3>;
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struct EulerBeam3DGeometry {
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Vector3 node1;
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Vector3 node2;
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Vector3 orientation;
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};
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Matrix12 euler_beam_3d_global_stiffness(const EulerBeam3DGeometry& geometry,
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const EulerBeam3DSection& section);
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Vector12 euler_beam_3d_global_end_forces(const EulerBeam3DGeometry& geometry,
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const EulerBeam3DSection& section,
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const Vector12& global_displacements);
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```
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Implementation rules:
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- local `x` is normalized `node2 - node1`
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- local `y` is the normalized projection of `orientation` onto the plane normal to local `x`
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- local `z = x cross y`
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- use the same 3x3 rotation block for translational and rotational DOFs
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- compute `K_global = T^T K_local T`
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- compute global end forces by transforming global displacements to local, recovering local forces, then transforming forces back to global
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- throw `std::invalid_argument` for zero-length element, zero orientation vector, or orientation parallel to the beam axis
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## Tests To Write First
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Create `/tests/unit/euler_beam_3d_transform_recovery_test.cpp` before production code.
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Test behavior:
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- Axis-aligned beam from `(0,0,0)` to `(2,0,0)` with orientation `(0,1,0)` gives global stiffness equal to local stiffness.
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- A rotated beam preserves stiffness symmetry.
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- A rigid global translation vector produces near-zero global end forces.
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- A simple global axial extension on the axis-aligned beam produces equal and opposite axial end forces.
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- Parallel orientation vector throws `std::invalid_argument`.
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RED command:
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```powershell
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ctest --test-dir build/msvc-debug --output-on-failure -C Debug -R euler_beam_3d_transform_recovery_test
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```
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Expected RED: test executable missing or compile failure because the transform API does not exist.
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Then implement the minimal API.
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GREEN command:
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```powershell
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ctest --test-dir build/msvc-debug --output-on-failure -C Debug -R euler_beam_3d_transform_recovery_test
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```
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## Acceptance Criteria
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```powershell
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ctest --test-dir build/msvc-debug --output-on-failure -C Debug -R "euler_beam_3d_(local_stiffness|transform_recovery)_test"
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python -m unittest discover -s scripts -p "test_*.py"
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python scripts/validate_workspace.py
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```
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## Verification Notes
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1. Confirm RED failed before production code was added.
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2. Confirm local stiffness tests still pass.
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3. Update `phases/euler-beam-3d/index.json` step 8:
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- success: `"status": "completed"`, `"summary": "global transform and global end-force recovery added for 3D Euler beam"`
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- failure after retries: `"status": "error"`, `"error_message": "<specific error>"`
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- blocked: `"status": "blocked"`, `"blocked_reason": "<specific reason>"`
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## Forbidden
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- Do not add assembly or solver integration in this step.
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- Do not modify reference artifacts.
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