Analyse the frame

The Analysis tab at the bottom finds the forces in every beam, column and brace of the model, the reactions at the column bases and how far the members bend, for the loads you give it.

Run it

1. Open the Analysis tab.
2. Select one or more members in the view, pick a Case, a Load and a Direction, type the value and press Add load. A load spread along a member is in kN/m, a point load in kN. Down (gravity) is the usual one.
3. Press Run analysis.

The table lists each member's largest axial force N, shears Vz and Vy, bending moments My and Mz, torsion T and its deflection, largest moment first; click a member's name to select it. Below are the reactions at each support. On the model draws the deflected shape, or one action as a diagram beside each member with its largest value written at its place. The results go out of date as soon as the model changes: run it again.

Every load, case and setting is one undo step (⌘ZCtrl+Z) and is saved in the model file.

Load cases and combinations

The analysis starts with three: Dead (the members' own weight, from their drawn sections and 7850 kg/m³), Live (empty) and Dead + live. Add cases of your own (wind, snow …) and combinations: a combination adds the cases up with the factors you type. The analysis is linear, so each case is solved once and combinations are sums. Type the factors your design code asks for; DetailCraft does not choose them.

What the frame is made of

• Beams, columns and braces, each on its work line (the line you drew), with the section's real properties worked out from its outline. Plates, stairs, footings and bolts are not part of the frame.
• A member is split where another member's end lands on it, so a beam framing into a column at mid-height joins the column there.
• Column bases: fixed (the start) or pinned (held in place and against twisting, free to turn). A base plate always makes a support.
• Beam ends: an end plate is rigid, a shear tab is pinned. Beam ends with no connection sets the rest. Braces are pinned at both ends.
• Select one member to give its ends, or a column's base, a rule of its own.
• Steel everywhere: E = 200 GPa, G = 77 GPa.

If the frame can move without bending anything — a mechanism, such as pinned bases with no bracing in one direction — the run stops and says where and which way; hold it there with a support, a rigid joint or a brace.

Signs

N > 0 is tension. My > 0 puts the member's local −z side in tension: a beam sagging under gravity has My > 0. Mz > 0 puts the local −y side in tension. Deflection is measured from the straight line between the member's ends. A member's local z points up (for a column: along X); its local axes turn with the member's rotation.

The report

Report (PDF) and Report (CSV) hold everything: the assumptions the frame was built on, sections, cases and combinations, then for each case and combination the reactions (with the sums of loads and reactions, which balance), the member forces and the displacements, and an envelope of every case. Export as CraftScript writes the same frame as a script for PartCraft's Script workspace, where the library function frame3d solves it step by step in readable code.

Method

The direct stiffness method, first order and linear: two-node beam-columns with axial, torsion and two bending stiffnesses (no shear deformation, no warping), end releases by static condensation, loads along members through the members' own shape functions. Its answers are checked against the classic textbook cases (cantilevers, simple, fixed and continuous beams, a portal frame, a grid in torsion, a truss).

Not built yet: second-order (P-Δ) effects, buckling, dynamic and seismic analysis, area and wind loads made for you, member offsets, tension-only braces, design code checks. See Not built yet.