Structural analysis in Python

Two ways to run it

Eurocode 3 checks from a script

A plain model gives you forces. check_beam goes one step further: it adds a ULS combination and an EN 1993-1-1 member check over the span, so one call returns bending, shear, combined N+M and lateral-torsional buckling utilizations with the per-clause trace behind each.

from fers_core import check_beam

# 7.5 m simply supported IPE400 in S275, 12 kN/m characteristic, ULS factor 1.35
beam = check_beam(7.5, "IPE400", material="S275", udl=12_000, uls_factor=1.35)
beam.run_analysis()

for row in beam.unity_check_results():
    print(row["governing"]["demand"])
# 0.8002749049232664

Buckling lengths default to the full span for a single-member model, so if the compression flange is restrained along its length — by decking, by a slab, by purlins — that is a modelling decision you make explicitly rather than one the default quietly makes for you. The worked EC3 example shows the same check with every clause written out.

The thing a web form cannot do

Five sections, five solves, one loop:

import os
import requests

KEY = os.environ["FERS_API_KEY"]

for section in ["IPE300", "IPE330", "IPE360", "IPE400", "IPE450"]:
    response = requests.post(
        "https://ferscloud.com/api/sdk/check-beam",
        headers={"X-API-Key": KEY},
        json={
            "span_m": 7.5,
            "section": section,
            "material": "steel_S275",
            "support": "simply_supported",
            "udl": 12.0,                       # kN/m, characteristic
            "idempotency_key": f"sweep-{section}-7m5",
        },
        timeout=60,
    )
    response.raise_for_status()
    check = response.json()["check"]
    print(f"{section:<8} UC {check['governing_utilization']:.3f}"
          f"  governed by {check['governing_check']}")

That is the argument for scripting a structural calculation. The marginal cost of the sixth variant is one more entry in a list, not another twenty clicks — and the same loop works over spans, load cases, steel grades, or a CSV of members exported from your model. What it reports is which limit state governs and by how much; which section you then choose is your call, not the script's.

Pass a stable idempotency_key and reuse it on retries: a repeat with the same key replays the stored result instead of charging a second solve.

Call it from any language

curl -s https://ferscloud.com/api/sdk/solve \
  -H "X-API-Key: keyId.secret" \
  -H "Content-Type: application/json" \
  -d '{ "model": { /* FERS model JSON */ }, "idempotency_key": "run-123" }'

Endpoints: solve, validate, check-beam, create-beam, sections, schema, models and me, all under /api/sdk/. The full machine-readable spec is at ferscloud.com/api/openapi.json.

Two habits save a lot of grief. Call validate before solve — it is free and it catches broken references and misspelled keys that the solver would otherwise silently resolve to a default. And ask schema for the contract rather than guessing field names, for the same reason.

Use it from an AI agent

The same solver is exposed as a remote MCP server, so Claude, ChatGPT, Cursor and VS Code can call it directly:

{
  "mcpServers": {
    "fers": {
      "url": "https://ferscloud.com/api/mcp",
      "headers": { "X-API-Key": "keyId.secret" }
    }
  }
}

The clients, the one-click installers, the OAuth flow and the full tool list are on the MCP server page.

Units, axes and sign conventions

Metres, newtons and newtons per metre in the Python layer; elastic modulus in pascals; deflections come back in metres, so multiply by 1000 for millimetres. The REST beam helpers take kN and kN/m, which is why the sweep above passes 12.0 where the local call takes 12_000.

The axis convention catches everyone once: i_z is the strong (major) axis and i_y the weak one. The full set of axis, sign and unit conventions is written out on the modeling conventions page, and it is the first thing to read if a result comes back an order of magnitude off.

What it costs

The Python package is free to install and the solver runs locally, with a 100-member ceiling on the free tier. Hosted solves — REST and MCP — are free for the first 100 successful solves per rolling week, then charged from a prepaid balance, or unlimited on Pro at €19.95 a month. Only successful solves are charged. See pricing.

Frequently asked questions