SpanDraft

SpanDraft is an open-source desktop application for intuitive beam analysis.

It is designed for mechanical-engineering workflows between hand/Excel calculations and large general-purpose FEM systems: define one straight beam, place supports and loads directly in a technical sketch, edit exact dimensions and inspect the resulting structural response.

SpanDraft has an initial public release, v0.1.0, and remains under active development. This README describes the current checkout, including changes made after that release.

Current capabilities

The current desktop application supports:

• one straight beam with constant material and cross-section
• parametric and manual cross-section setup
• built-in and custom material libraries
• reusable custom section presets
• explicit bending-axis selection
• fixed, pinned and roller supports
• point forces and point moments
• constant distributed loads
• direct graphical placement and editing
• exact numeric positioning
• schematic layout for dense models without changing physical coordinates
• undo and redo
• versioned .spandraft project files
• crash recovery
• project information with calculation title, author, optional project title and reference
• automatic analysis after committed model changes
• compact display of maximum deflection, bending moment, bending stress and safety factor against the material's yield or proof strength
• calculation report preview, PDF export and Windows printing
• German and English interface text, independent regional number formatting and configurable technical units and display precision

The numerical core provides support reactions and continuous analytical fields for displacement, rotation, axial force, shear force and bending moment.

The desktop displays support reactions and live diagrams for displacement, shear force and bending moment. Reports capture confirmed project inputs, existing results and calculation assumptions.

The published Windows x64 release uses an Inno Setup installer. The current checkout also provides an independent Microsoft Store/MSIX packaging path; see RELEASING.md for both workflows and their prerequisites.

Engineering scope

SpanDraft currently uses a linear-elastic Euler-Bernoulli beam formulation with small displacements and rotations.

The current model is intentionally focused on small single-beam problems. It is not a general-purpose FEM system and does not provide nonlinear analysis, buckling, fatigue, contact, 2D/3D frames or normative design verification.

The displayed bending stress and safety factor are simple elastic assessments, not a code-based structural verification.

Built-in material properties are curated SpanDraft reference values assembled from publicly available technical information and cross-checked against multiple sources. They do not replace material standards, manufacturer specifications or material certificates.

The solver has been independently validated against analytical references, IndeterminateBeam and PyCBA. See VALIDATION.md for the validation scope and evidence.

Development

Requirements:

• .NET 10 SDK

Windows is the primary target. Development on macOS and Linux is supported.

From the repository root:

dotnet restore SpanDraft.sln
dotnet build SpanDraft.sln --no-restore
dotnet test --solution SpanDraft.sln --no-build --no-restore
dotnet run --project src/SpanDraft.Desktop

GitHub Actions runs the product, independent validation and offline help gates on pushes to all branches and pull requests targeting main.

On macOS, Desktop builds also create a development SpanDraft.app bundle inside the corresponding build output. It uses the locally installed .NET runtime and is intended for development only.

Third-party notices

After changing Desktop dependencies, regenerate and commit THIRD_PARTY_NOTICES.txt:

dotnet run --file scripts/generate-third-party-notices.cs

Verify the committed file with:

dotnet run --file scripts/generate-third-party-notices.cs -- --check

Desktop builds and publishes ship the committed file beside the application.

Architecture

The application is split into small layers with explicit responsibilities:

Project	Responsibility
SpanDraft.Core	domain model, units and validation
SpanDraft.Solver	Euler-Bernoulli beam mechanics
SpanDraft.Engineering	elastic engineering assessment
SpanDraft.Analysis	application-facing analysis orchestration
SpanDraft.Desktop	Avalonia desktop application
SpanDraft.Reporting	frozen A4 report composition for preview, PDF export and Windows printing
SpanDraft.Tests	product and regression tests

Core is independent of UI, numerical libraries, persistence and reporting. Desktop consumes the analysis API rather than implementing mechanical formulas itself.

Documentation

• KONZEPT.md — product vision, scope and roadmap
• DOMAIN.md — domain model, units and sign conventions
• SOLVER.md — numerical formulation and solver contract
• ENGINEERING.md — engineering assessment and limits
• ANALYSIS.md — application analysis API
• UI.md — rationale for editor state and interaction
• PROJECT_FORMAT.md — .spandraft file format
• LIBRARIES.md — built-in materials and local reusable libraries
• VALIDATION.md — independent solver validation
• RELEASING.md — release and packaging workflows

License

SpanDraft is licensed under the GNU General Public License v3.0. See LICENSE. Third-party package notices are listed in THIRD_PARTY_NOTICES.txt.