FERS — structural FEM MCP server

FERS: structural analysis in Python

FERS: structural finite-element analysis (3D frames, trusses, plates, Eurocode 3 checks) for engineers and AI agents. This is its Python SDK and the fers command. The solver is a compiled engine that runs on your machine, with no account and no network call: free for non-commercial use up to 100 members.

pip install FERS

from fers_core import check_beam

# IPE200 in S235, simply supported over 6 m, 10 kN/m. SI units: m, N, Pa.
# check_beam adds an EN 1993-1-1 member check on a ULS combination of 1.35 x the load.
model = check_beam(6.0, "IPE200", udl=10_000.0)
model.settings.analysis_options.include_member_deflected_shape = True
model.run_analysis()

beam = model.resultsbundle.loadcases["Q"].member_results["1"]
x_frac, (_, dy, _) = beam.member_displacement_peak
ec3 = model.unity_check_results()[0]
print(f"M {beam.local_minimums.mz / 1e3:.1f} kNm, sag {dy * 1e3:.1f} mm at x/L {x_frac:.2f}")
print(f"EC3 utilization {ec3['max_utilization']:.2f}")

M -45.0 kNm, sag -41.8 mm at x/L 0.50
EC3 utilization 2.85

The sag is 41.3 mm of bending (5wL⁴/384EI) plus 0.4 mm of shear deformation, which the engine includes. The beam fails: the ULS moment of 60.75 kNm exceeds its bending resistance of 51.9 kNm, and with nothing restraining its compression flange, lateral-torsional buckling takes the utilization to 2.85.

model JSON file, print one line (or --json) and say in their exit code whether the numbers can be used; see From the terminal and from coding agents. fers skill --install . gives a coding agent the FERS skill, and MCP clients can use the FERS MCP server. In Claude Code, both come as one plugin: /plugin install fers --marketplace Jeroen124/FERS_core.

• Agents and scripts: fers solve, fers check and fers validate take a

your own dimensions ("FERS[sections]") and DXF import ("FERS[dxf]"); "FERS[all]" installs everything 0.1.x did. Catalogue sections (IPE200, HEB300, UB 457x191x67, W14X30, ...) need no extra.

• Extras: plots (pip install "FERS[plot]"), section properties meshed from

non-commercial use (Licence).

• Licence: the SDK is BSD-3-Clause; the engine it installs is free for

Solving a model

Building a model by hand, create the FERS object first, then its nodes, members and loads. Creating a FERS restarts the id counters, so a node made before it would share an id with one made after it, and the solver refuses node ids that do not run from 1 without gaps.

Reading results

run_analysis() puts the results on model.resultsbundle. Load cases and load combinations are keyed by name. Within each, nodes and members are keyed by their id as a string, because results round-trip through JSON.

case = model.resultsbundle.loadcases["Load"]    # or .loadcombinations["ULS 1"]

case.displacement_nodes["5"].dy                  # dx dy dz rx ry rz warp
case.reaction_nodes["1"].nodal_forces.fy         # fx fy fz mx my mz bw
beam = case.member_results["4"]
beam.local_maximums.mz, beam.local_minimums.mz   # envelope along the member
beam.local_start_forces.fy                       # end forces, member axes

Since 0.1.98, memberresults and displacementnodes are read-only tables rather than dicts of objects. That is what keeps a large result small in memory. They read like dicts: [], get, in, len, .items(), and iteration in the solver's order. Each lookup builds a fresh object, and nothing in it can be changed:

beam.local_maximums.mz = 0.0                     # AttributeError: read-only
editable = case.member_results.copy()            # a plain dict of editable objects
editable["4"].local_maximums.mz = 0.0            # fine

Shortened. The full README is on GitHub.