FEMur API Reference

FEMur's core library (FEMur.dll) can be called directly from a Grasshopper C# script component or from any .NET application. This reference documents its public .NET API.

The per-type pages are generated from the source and are English only.

A minimal analysis

Solving a cantilever (2 m of H-200x100, 1 kN at the tip) and reading the tip deflection:

using System;
using System.Collections.Generic;
using FEMur.CrossSections;
using FEMur.Elements;
using FEMur.Geometry;
using FEMur.Loads;
using FEMur.Materials;
using FEMur.Models;
using FEMur.Nodes;
using FEMur.Solver;
using FEMur.Supports;

// 1. Create the nodes. Units are mm. The first argument is Node.Id
var n1 = new Node(0, 0.0, 0.0, 0.0);
var n2 = new Node(1, 2000.0, 0.0, 0.0);

// 2. Material and cross-section (arguments: name, b, h, t_f, t_w, r)
var steel = Material_Isotropic.Steel();
var section = new CrossSection_H("H-200x100", 100.0, 200.0, 8.0, 5.5, 8.0);

// 3. Element
var beam = new BeamElement(0, n1, n2, steel, section);

// 4. Support: fix the node whose Id is 0
var support = Support.Fixed(0);

// 5. Load: 1000 N in -Z at the node whose Id is 1
var load = new PointLoad(1, new Vector3(0.0, 0.0, -1000.0), new Vector3(0.0, 0.0, 0.0));

// 6. Assemble the model
var model = new Model(
    new List<Node> { n1, n2 },
    new List<ElementBase> { beam },
    new List<Support> { support },
    new List<Load> { load });

// 7. Solve. Solve does not modify the model; it returns a SolveOutcome
var outcome = new LinearStaticSolver().Solve(model);

// 8. Tip deflection, looked up by node Id
double uz = outcome.Combined.GetDisplacement(1).Uz;
Console.WriteLine($"Tip deflection UZ = {uz:F4} mm");

Output:

Tip deflection UZ = -0.7435 mm

This matches the Timoshenko beam result PL³/(3EIyy) + PL/(Asz·G).

What you need to know before using the API

Some contracts cannot be read from the type signatures. Getting them wrong produces a wrong answer without raising an error.

Units are fixed to N and mm

Quantity	Unit
Length, coordinates, displacement	mm
Force, axial force, shear force	N
Moment	N·mm
Stress, Young's modulus	N/mm²
Mass	kg

There is no mechanism for switching unit systems. Do not mix units.

An Id is not a list index

The number in Support.Fixed(0) and new PointLoad(1, ...) is a Node.Id, not the position of the node in Model.Nodes.

In the example above the two happen to coincide because new Node(0, ...) and new Node(1, ...) set the Id explicitly. They will not coincide if you assign ids independently of creation order. Always address nodes by their Id.

Look up results by node Id or element Id

Result.GetDisplacement(nodeId) returns the displacement of that node as a NodalDisplacement. Its components are the translations Ux, Uy, Uz (mm) and the rotations Rx, Ry, Rz (rad).

var d = result.GetDisplacement(nodeId);
double uz = d.Uz;

An Id that is not in the model throws KeyNotFoundException. Use TryGetDisplacement to check first. To visit every node, iterate Result.NodalDisplacements and identify each entry by its NodeId.

Reactions, element stresses, shell stresses and the stresses of axisymmetric and plane elements work the same way: GetReaction(nodeId), GetElementStress(elementId), GetShellStress(elementId), GetAxisymmetricStress(elementId) and GetPlaneElementStress(elementId). Mode shapes from an eigenvalue analysis are available through EigenResult.GetModeShape(modeIndex, nodeId).

Truss elements only use the three translational degrees of freedom, but results are always expanded to six degrees of freedom for compatibility.

Developing with an LLM

Two plain-text files describe the whole API.

File	Contents	Use
/llms.txt	Index of every public type with a one-line description	Start here; enough for most tasks
/llms-full.txt	Every public type and member with its exact C# signature	When you need completeness

Two ways to use them:

1. Give the URL to your LLM — "Read https://femur.jp/llms-full.txt and write C# that solves a cantilever."
2. Save the file locally — drop it into your project folder and the model can read it offline.

llms-full.txt states explicitly that anything not listed there does not exist in the public API, which discourages the model from inventing methods.

Namespaces

The sidebar lists every namespace and type.

Namespace	Contents
FEMur.Models	Model — the analysis model container
FEMur.Nodes	Node
FEMur.Elements	BeamElement / TrussElement / ShellElement / AxisymmetricElement / PlaneElement (plane stress / plane strain)
FEMur.CrossSections	H, box, circle, pipe, rectangle, T, L, channel, custom, shell thickness
FEMur.Materials	Material_Isotropic / Material_Orthotropic
FEMur.Supports	Support — boundary conditions and spring supports / SurfaceSpring — surface springs on shell elements
FEMur.Loads	Point, distributed, line, surface, floor, edge pressure (axisymmetric and plane elements), self-weight, prescribed displacement, time-history loads (ground motion, time functions, damping) and more
FEMur.Joints	Joint — semi-rigid connections via end springs
FEMur.Constraints	RigidDiaphragm / DofCoupling — coupled degrees of freedom
FEMur.Solver	LinearStaticSolver / EigenSolver / TimeHistorySolver / SolveOutcome
FEMur.Results	Result / NodalDisplacement / ElementStress / ShellStress / AxisymmetricStress / PlaneElementStress / ReactionForce / EigenResult / TimeHistoryResult
FEMur.Geometry	Point3 / Vector3 / LocalFrame — local frames at nodes
FEMur.Export	MGT import and export
FEMur.Common.Units	Unit definitions and conversion