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File Formats

A .x2d file is a ZIP archive containing:

Entry Contents
structure.json the full model (nodes, elements, materials, sections, supports, springs, constraints, loads, load cases, analysis cases, combinations, spectral functions, nodal masses)
results.json analysis results, when present — including any reinforcement / steel / timber design payloads and the design code they were produced with (which takes precedence over the preference default on reopen)
stiffness_<id>.npy stored tangent stiffness matrices from P-Delta runs
snapshots.json the named snapshots, when there are any: name, date/time and the model of each (no results)
view.json display options, selection, and Scenes (with per-scene zoom)

This is the default for Save / Open and preserves everything, including the view state.

.json — structure only

A plain JSON export of the model (no results, no view state). Useful for interchange and version control.

Migration of combinations

When an older model that stored load-case factors directly in combinations is opened, xdfem2D folds each such factor into a Linear analysis case and rewrites the combination to reference that analysis case. This keeps the three-tier model consistent and is applied automatically on load and before solving.

Units

All files use the program's units throughout: kN · m · kNm (and t for mass).