Concepts

Understanding the core data model before diving into the API.

StructuralModel

The central object. A StructuralModel holds all nodes, members, supports, materials, sections, loads, load cases, and load combinations. After analysis, it also holds the AnalysisResultSet.

StructuralModel
├── Nodes              — points in 3D space
├── Members            — beam/truss elements connecting two nodes
├── Supports           — boundary conditions at nodes
├── Materials          — steel grades, concrete classes
├── Sections           — cross-section geometry (I-beam, rectangular, circular, etc.)
├── NodalLoads         — forces/moments applied at nodes
├── DistributedLoads   — loads along member length
├── LoadCases          — groups of loads by type (dead, live, wind, ...)
├── LoadCombinations   — factored combinations of load cases
└── Results?           — AnalysisResultSet (null until analysis is run)

Nodes

A node is a point in 3D space with an integer ID. Nodes are where members connect, supports are applied, and nodal loads act.

Members

A member connects two nodes. Each member has a material, a cross-section, and a type (Beam or Truss). Beam elements have 6 DOF per node (3 translations + 3 rotations). Truss elements have only axial stiffness.

Members can have intermediate nodes, splitting them into segments for finer resolution.

Supports (boundary conditions)

Supports restrict degrees of freedom at a node. Common types:

Type	Translations	Rotations	Use case
Fixed	All restrained	All restrained	Rigid connections to ground
Pinned	All restrained	All free	Simple supports
Roller	Uy restrained only	All free	Expansion joints
Free	All free	All free	No support (default)

Load cases

A load case groups loads that act simultaneously and share a load type: dead, live, wind, snow, seismic, or ice. Each load case is solved independently by the FEM solver. Load cases carry metadata relevant to their type (wind direction, ground snow load, seismic coefficients).

Load combinations

A load combination applies partial safety factors to load cases and superposes the results. For example, a Eurocode ULS combination might be 1.35 × Dead + 1.5 × Live. Combination results are computed via linear superposition — no re-solving needed.

Analysis results

After running analysis, Model.Results contains an AnalysisResultSet with:

• Node displacements — Dx, Dy, Dz, Rx, Ry, Rz per node per load case/combination
• Reactions — Fx, Fy, Fz, Mx, My, Mz at supported nodes
• Member forces — N, Vy, Vz, Mx, My, Mz at stations along each member
• Utilization — design check ratios with governing clause references (if a design code is selected)

Results are stored as flat lists and queried by node ID, member ID, load case, or as envelopes (max/min across all scenarios with traceability to the governing load case).

Invalidation

Any model mutation (adding a node, changing a load, moving a support) automatically clears Model.Results. This ensures you never see stale results.