> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/templates/openbrimfea/properties-fea.md).

# Properties \[FEA]

The Properties branch holds the material and section definitions that turn geometry into stiffness.

**Materials** supply modulus, Poisson's ratio, density and thermal expansion - the properties that drive the analysis - plus the strength values and time-dependent behaviour used by design and staged construction. **Sections** supply the cross-sectional properties: area, moments of inertia, torsion constant and shear areas.

**Rebars** and **Strands** are property library entries describing bar and strand sizes. They are used by design and section analysis; they do not create elements of their own.

These objects are referenced by name from elements, so one definition serves many members - and a change to a material or section propagates to every element that uses it.


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