Tools › User guides › 2D Frame / Beam / Truss
The 2D Frame / Beam / Truss tool solves any plane beam, frame or truss by the direct stiffness method (the matrix method STAAD uses) and draws the bending moment, shear force and axial force diagrams with values, the deflected shape and the reactions.
Open the Beam, Frame & Truss Analysis ›
| Tool | How to use | — | Tip |
|---|---|---|---|
| Start from an example… | Simply supported, cantilever, continuous, two EIs, Gerber beam, three-hinged / portal / two-storey frame, Pratt truss. | — | |
| Select | Tap a member to set material, section, E, I, A or EI multiple; tap a node to type x, y. | — | |
| + Node / + Member | Tap the grid to add nodes; tap two nodes for a member (drawing continues; Esc to stop). | — | Nodes snap to the grid; type exact coordinates on the Grid tab. |
| Support | Tap a node: 1st pin, 2nd roller, 3rd fixed, 4th none. | — | Pick a horizontal roller from the list when the node is selected. |
| Hinge | Tap a node for an internal hinge, or a member to insert one. | — | Too many hinges make a mechanism. |
| Load | Tap a member (point, UDL, varying, moment) or a node (force, moment). | — | Distances from the member start node. “Down” is vertical; “Perpendicular” is normal to the member. |
| Delete / Undo / Fit / Numbers | Edit and view. | — | Ctrl+Z undoes. |
| Property | Unit | Example | Tip |
|---|---|---|---|
| Lengths, forces, moments | m, kN, kN·m. | ||
| E | N/mm². | Concrete 25 000; steel 200 000 | |
| I | ×10⁶ mm⁴. | 300 × 300 mm section = 675 | |
| A | mm². | ||
| Default section / Apply to every member | New members get this section. | For a determinate structure moments do not depend on EI. |
Press Analyse and switch between Bending moment (drawn on the tension side; beams: + sagging, − hogging), Shear force, Axial force (+ tension red, − compression blue), Deflected shape (mm) and Reactions (Rx + right, Ry + up, M + anticlockwise). Tables with every value are below the drawing. Save file / Open file move a model between devices; Print / PDF prints it.
| Message | What to do |
|---|---|
| Unstable | Add a support or member, change a roller to a pin, or remove a hinge. |
| Moment at a pinned joint | Put the moment on a member instead of a fully pinned node. |
| Equilibrium does not close | One member is far stiffer than the rest — check its E, I and A. |
Yes — continuous beams, portal frames and multi-storey plane frames, using the stiffness method. Only the ratio of EI matters for moments.
No: linear elastic, small deflections, plane structures only.