Why a model appears
The palette at a node is not the catalogue. It is the catalogue after the app has measured the node and removed everything that could not be built there. This page explains what gets measured, what removes a model, and what merely changes it.
What the app reads from the node
Before any model is judged, the node is measured. The measurement is geometric and has no opinion: it only reports what is there.
- The shape of the node: which member is the support, which is supported, and whether the column dies here or passes through.
- Which face the beam meets, flange or web, measured member by member rather than assumed from the node type.
- The profiles themselves: hot rolled or cold formed, whether there is a usable web, depth, flange width, web and flange thickness, and the fillet radius when the catalogue declares one.
- Skew in plan and slope in elevation, measured separately. They are different problems and they have different answers in the shop.
- Continuity you declared. Saying a beam runs continuous over a column changes what the node is for detailing purposes, even though no bar moved.
Not everything that is unusual is a refusal
The first version of this filter treated every rule as a yes-or-no condition. Checked against 121,699 real nodes, that turned out to be wrong: a sloped beam appears in 46.3% of nodes, and refusing all of them would have rejected almost half the archive over something a fabricator solves by cutting the leg at an angle. So a rule now has one of three natures.
Condition: it does not fit
The model disappears from the palette and the reason is written out. A cold-formed beam under a rule the code does not cover is a condition: no detail choice rescues it.
Caveat: it fits, but the piece changes
The model stays available and the note stays visible. A sloped beam still takes the connection, with the leg cut to the angle. A caveat may never block, and may never stay quiet.
Variant: it is a different piece
Welded to the support and bolted to the beam is not the same connection as bolted on both sides: it has its own limit states, its own drawing and its own arithmetic. Variants are offered as separate options, not folded into one card.
What real nodes look like
The rules were calibrated against the geometry of real projects, not against a textbook idea of a node. Four numbers from that sweep, which explain most of what the palette does:
92.5%
of nodes are square in plan, within 2 degrees. Skew is a corner case, and it needs a bent angle, which is not a catalogue profile.
46.3%
have a beam sloped by more than 15 degrees. This is a caveat, never a refusal.
72.5%
carry two or more supported beams, so the palette has to reason about more than one end.
79.5%
of column-web nodes have a beam that fits between the flanges. The remaining fifth is why the fit is measured and not assumed.
When the palette comes back empty
An empty palette is a statement, not a bug, and the reason is always printed next to the model that was removed. The three that come up most often:
There is no beam end here
You declared the beam continuous through the node, so the end-of-beam models have nothing to attach to. Detail the member that does end here instead.
The profile has no usable web
Models that bolt to a web cannot be offered on a section that does not have one. Look for a seated or flange-based model.
The beam does not fit between the flanges
On a column-web node the beam has to physically clear the flanges. When it does not, the fit test removes the model rather than drawing steel through steel.
Among the models that survive the filter, one is marked as the default for that node shape. It is a starting point chosen from what is usual, not a recommendation about your structure: the check is what decides, and the check runs on whichever model you keep.