> 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/result-combinations-fea.md).

# Result Combinations \[FEA]

Result Combinations holds the objects that turn raw analysis output into the values a design check needs. Everything here is **result-time post-processing** - none of it re-analyses the model.

**Combinations & Envelopes** factor and sum cases into design combinations, or envelope alternatives where the governing case varies by location. **Combination Items** express the individual case-and-factor pairs, and are the better route for anything non-trivial.

**FE Composites** merge the forces of several elements onto one section at its centre of gravity, which is what a section capacity check requires when a girder is modelled with separate shell and beam elements. **Concurrent Force/Displacement Requests** report one quantity at the instant another is at its extreme - the pairing an interaction check needs, and one that envelopes cannot provide.

**Equivalent Stiffness** condenses a region of the model into a single 6x6 stiffness matrix for handing to another model.

One rule governs this whole branch: combination by superposition is valid for **linear** results only.


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