How it works

• A real finite-element solver, not a formula. Members are 3D beam elements with axial, bending and torsion stiffness (shear deformation is neglected, as in classic frame analysis); the second-order run iterates the P-Δ effect of axial forces on the deflected geometry until it converges.
• Checked against an independent solver. On a test portal frame the linear results match a second, independent nonlinear finite-element engine to 15 digits and the P-Δ results agree within 0.2%. On the default building above, second order, the support reactions agree within 0.05% and the largest deflection within 0.01 mm.
• Every run proves its own equilibrium. The sum of the support reactions is compared with the sum of every load you applied, including self-weight. If they do not match, you see it.
• Sections from dimensions. I-section properties are computed from height, width, web and flange thickness and the root radius; for the 46 standard IPE, HEA and HEB sections in the list, area and bending stiffness come out within 0.5% of catalogue values, most within 0.1% (torsion within about 3%).

What this tool does not do: it gives elastic forces and deflections, not a code check. Member buckling, connection design and load combinations to a design code are part of a real design.

Use it from an AI assistant

An AI assistant can give you a ready-to-run analysis: it builds a link to this page with your model in it, and the page solves it in your browser when you open it. Nothing is sent to a server. Assistants with the Structomat MCP server (https://structomat.com/mcp/) can call prepare_frame_analysis; any assistant can also write the link itself:

• Mono-pitch canopy: https://structomat.com/frame-analysis/#t=mono&S=12&H1=4&H2=5.5&N=5&B=5&base=pinned&col=HEA+300&beam=IPE+400&G=0.3&Q=0.75&W=0.5&fG=1.35&fQ=1.5&fW=0&an=pdelta&run=1 (S span, H1 low side, H2 high side, N frames, B spacing, m; W net roof wind, + uplift)
• Portal frame building: #t=portal&S=20&H=6&R=1&N=5&B=6&… (S span, H eave height, R ridge rise, N frames, B spacing; W windward wall pressure and Ws leeward suction in +X)
• Multi-storey frame: #t=storey&nx=3&nz=2&ns=3&ax=6&az=5&h=3.5&… (bays in X and Z, storeys, bay widths, storey height)
• Common parameters: base fixed or pinned; col, beam a standard European I-section written like IPE+360 or HEA+280: IPE 160, 180, 200, 220, 240, 270, 300, 330, 360, 400, 450, 500, 550, 600; HEA and HEB 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 400, 450, 500, 550, 600 (any other name is replaced by the default and the page says so; for another section send the full JSON below with its A, Iy, Iz, J); G dead and Q live or snow load in kN/m² (member self-weight is added); fG, fQ, fW combination factors; an pdelta or linear; run=1 solves on open. Steel is E = 210 GPa, G = 81 GPa; the steel grade (S235, S355, …) does not change an elastic analysis, it matters only in the code check.
• Any other frame: #json= followed by the URL-encoded model JSON, then &run=1. Units kN and m, Y vertical: {"nodes":{"A":[0,0,0],"B":[0,4,0]}, "members":[{"id":"C1","i":"A","j":"B","sec":"COL","pinned":false}], "sections":{"COL":{"A":0.0077,"Iy":2.77e-5,"Iz":7.76e-5,"J":4.2e-7}}, "supports":{"A":"fixed"}, "nodeLoads":[{"node":"B","case":"W","F":[2,0,0]}], "memberLoads":[{"member":"C1","case":"G","dir":"FY","w":-1}], "combo":{"G":1.35,"Q":1.5,"W":1}, "selfWeight":true, "analysis":"pdelta"} (sections in m² and m⁴, Iz strong axis; member loads in kN per metre in global FX, FY, FZ; pinned releases bending at both ends). If the link is too long for the chat, paste the JSON under “Model as JSON” above.
• Reading the results: when the solution finishes, the page shows “Results as JSON” (element #resOut): equilibrium check, largest displacement and sway, every support reaction and the forces of every member, with units and sign convention. An assistant that can open the page can read the numbers there instead of parsing the tables.