Pieces
A structural model splits a member at every node, and a node appears wherever something lands on it. A twelve metre chord with eight purlins on it is nine bars in the model and one piece of steel in the shop. Creating a piece is how you tell the app which one it is.
A piece is a path, not a new bar
You pick two nodes and the piece is the chain of bars running between them. It has to be a path, because creating a single long bar instead would delete the nodes in between, and with them every connection of every purlin that lands there. The model keeps its nodes; the piece is a declaration laid over them.
What it accepts, and what it refuses
Refuses
- The same node clicked twice.
- No collinear path between the two nodes.
- The path changes profile halfway. That is not one piece of steel.
- A bar on the path already belongs to another piece.
Accepts
- A path of one bar. A piece can be a single bar.
- A path through ten nodes, or more.
- Bars with no profile yet. The piece can exist before anyone sizes it.
Collinear means within 1.5 degrees, which is the same threshold the drawing uses to decide that two bars are the same steel and erase the line between them. One threshold, so what you see and what the piece accepts never disagree.
Declared steel outranks whatever wanted to cut it
Six independent mechanisms in the editor modify the end of a bar: node copes, drawing setbacks, joint bevels, trim bevels, ridge cuts on imported models, and weld bevels. A piece removes five of them from its own bars and keeps one. The weld survives because a piece welded to something is still a piece that left the saw whole.
| Mechanism | What it does to the end | On a piece |
|---|---|---|
| Node cope | Notches the flange against the web that supports it. | dropped |
| Drawing setback | Pulls the end back out of the member it runs into. | dropped |
| Joint bevel | Chamfers the end in the plane of the joint. | dropped |
| Trim bevel | Cuts at the angle of the extend-to tool. | dropped |
| Ridge cut | Trims the raw apex of an imported model. | dropped |
| End offset | Advances or pulls back the end along the axis. | dropped |
| Weld bevel | Chamfers against the face of whatever stays whole. | kept |
The end offset is dropped only at the internal joints of the chain. The two outer ends of the piece are ends of real steel, and what you set there still applies.
This changes the drawing, not the document. The connection is still at the node, still computed, still listed, and the offset is still on the bar. What the piece declares is that this steel leaves the saw in one length, and that is what the screen then shows. If the connection genuinely needs a cope, that is a decision for you: delete the piece, or change the connection model.
The name
A piece is named when it is created, and that name is what appears when you point at any bar in it. A bar can also carry a free name of its own; where a piece exists, the piece name wins, because showing the name of a fragment would contradict the declaration that it is one thing. Everywhere else, which is most of the model, the bar name still applies.
Names are not required to be unique, deliberately. Two identical trusses can both have a top chord, and forcing a number onto the second one would only invent a distinction that is not there.