Matrix (stiffness) analysis for a gable or flat-roof portal frame — pinned or fixed bases, gravity and wind load — with reactions, member forces and eave drift.
Per horizontal metre of plan area (dead + live/snow), not per rafter length.
Positive = rightward. Set to 0 to check gravity only.
Max moment
-109.44 kN·m
Max shear
-56.08 kN
Max axial
-62.67 kN
Eave drift
5.77 mm
↓ gravity · → wind · pinned base
| Base | Fx (kN) | Fy (kN) |
|---|---|---|
| Left | 19.36 | 57.33 |
| Right | -27.36 | 62.67 |
| Member | |M|max (kN·m) | |V|max (kN) | |N|max (kN) |
|---|---|---|---|
| Left column ● | 77.44 | 19.36 | 57.33 |
| Left rafter | 77.44 | 50.85 | 49.84 |
| Right rafter | 109.44 | 56.08 | 27.35 |
| Right column | 109.44 | 27.36 | 62.67 |
Click a member to see its diagrams below.
Peak -77.44 kN·m at 4.00m
Hover the chart to read a value at any point along the beam.
Peak -19.36 kN at 0.00m
Hover the chart to read a value at any point along the beam.
Peak -57.33 kN at 0.00m
Hover the chart to read a value at any point along the beam.
Positive axial = tension. Diagrams run from the member's first node (bottom of columns; left end of rafters) to its second. This is a serviceability/analysis estimate — section adequacy still needs checking against your governing design code.
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Ready to take the next step?
A rigid joint between a column and a beam means load applied anywhere in the frame affects moment and shear everywhere else in it — the frame "shares" the load in a way a single simply-supported beam never does. Once both bases provide any restraint at all, the structure is statically indeterminate, and there is no shortcut to statics alone; the actual distribution of forces depends on the relative stiffness of every member.
This calculator solves that properly with a direct-stiffness (matrix) method — the same underlying approach used by professional structural analysis software — rather than an approximation.