Analyse the structural frame

The Analysis tab on the right finds the forces in the open model's beams, columns and braces, the reactions at the column feet and how far the members bend, for the loads you give it.

Run it

1. Open an IFC model and the Analysis tab.
2. Pick one or more beams, columns or braces in the view, choose a Case, a Load and a Direction, type the value and press Add load: kN/m for a load spread along a member, kN for a point load.
3. Press Run analysis.

The table lists each member's largest axial force, shears, bending moments, torsion and deflection; click a member's name to pick it in the view. Below are the reactions. On the model draws the deflected shape, or one action as a diagram beside each member. The results go out of date when the model changes: run it again.

Each load and setting is one change in the Changes list: Undo takes it back, and Save as IFC keeps them in the file (the project's CadCraft_Analysis property set), so the next time the model opens here its loads are still there.

How the analytical model is made

• Every IfcBeam, IfcColumn and IfcMember whose shape is one straight extrusion becomes a member on its section's centroid line. Its section properties come from the profile: I, U, L and T shapes, rectangles and tubes, circles and round tubes, or any closed outline (then the torsion constant is an estimate, said in the report). Anything else is left out and counted.
• In a model, beams stop at a column's face and sit below the floor. Each member end is carried along its own line onto the axis of the member it frames into, when that axis is close (within about the size of the sections), and that member is split there. The report says how many ends moved.
• Column feet nothing goes below are supports: fixed (the start) or pinned (held in place and against twisting, free to turn).
• Beam ends are rigid or pinned by the Beam ends with no connection rule; braces (IfcMember) are pinned at both ends. Pick one member to give its ends, or a column's foot, a rule of their own.
• Materials by name: concrete (E = 30 GPa), timber (E = 11 GPa), otherwise steel (E = 200 GPa).

If the frame can move without bending anything — a mechanism — the run stops and says where and which way.

Cases, combinations, signs and the report

The analysis starts with Dead (own weight), Live and Dead + live; add cases and combinations with the factors your design code asks for. N > 0 is tension; My > 0 puts the member's local −z side in tension (a beam sagging under gravity has My > 0). Report (PDF) and Report (CSV) hold the assumptions, sections, cases, reactions with their sums, member forces, displacements and an envelope. Export as CraftScript writes the frame for PartCraft's Script workspace, where the library function frame3d solves it in readable code.

The method is the direct stiffness method, first order and linear, checked against textbook cases. Not built yet: P-Δ, buckling, dynamics, area loads, member offsets, tension-only braces, walls and slabs in the frame, design code checks. See Not built yet.