An applied moment at the eaves — crane brackets and eccentric connections
A load hung off the side of a column is not just a load — it is a load plus a moment. Here is where that moment goes, and why it reappears at a footing on the other side of the building.
- Span
- 6 m
- Height
- 4 m
- 40 kN·mapplied at the left eaves
- Equivalent
- 20 kN at 2 ma bracket load
- Bases
- pinned
Part 1 — A bracket hung off the column
An eccentric load IS a moment at the node.
The pinned portal again, with no distributed load at all:
N 0,0 N 0,4 N 6,4 N 6,0 M 1 2 M 2 3 M 4 3 S 1 P S 4 P
Instead, apply a moment of 40 kN·m at the left eaves — a crane bracket, a cantilevered walkway, or any load hung off the side of the column rather than through its center. In the Nodal Loads table, set the moment on node 2 to 40.
A 20 kN load on a bracket 2 m out is not a 20 kN load on the column — it is 20 kN plus 40 kN·m. Modelling only the vertical force is the classic eccentric-connection mistake, and this example isolates the part that gets forgotten.
Part 2, step 1 — A moment is resisted by a couple
Pure statics, and worth doing by hand.
No vertical or horizontal force was applied, so both reaction totals must be zero — and they are: 0 kN vertical and 0 kN horizontal.
The applied 40 kN·m still has to be balanced. With pinned bases 6 m apart, the only mechanism available is a vertical couple:
The solver returns -6.667 and 6.667 kN — the hand value exactly, and one of the bases is in uplift again.
Part 2, step 2 — Chasing the moment to the ground
It does not stay where you put it.
The peak member moment is 26.17 kN·m, and it is not confined to the column the bracket is bolted to. The moment applied at node 2 is shared out by the rigid joint into both the column and the rafter, travels across the frame, and finally leaves as the reaction couple.
Follow it: applied at the eaves → split between column and rafter → carried across the frame → resisted by ±6.67 kN at the feet. Every one of those steps is a check somebody has to do, and a connection somebody has to detail.
Hand calculation vs solver
| Quantity | By hand | StructureCalcs | |
|---|---|---|---|
| Total vertical reaction | 0 (no vertical load applied) | 0 kN | |
| Total horizontal reaction | 0 (no horizontal load applied) | 0 kN | |
| Reaction couple | M/L = 40/6 = ±6.67 kN | -6.667 / 6.667 kN | |
| Peak member moment | indeterminate | 26.17 kN·m |
Every value was worked by hand with the classical method, then checked against this site’s solver — the same engine the Try it button opens. This agreement is re-run automatically on every build.
Now make it yours
Open this exact model in the calculator — then change a load, drag a support, and watch every diagram update in real time. The best way to build intuition is to break it and see what happens.
Take it with you
Export this worked example as a PDF, or download it as a .screport and open it in the Report Builder — the model travels inside the file, so you can reconstruct it, re-solve, and build your own report from it.