With the Divide-Combine Single Intersections command, the wanted purlin is split at the main beams, columns and/or trusses or previously split purlins are combined.
Location of Divide-Combine Single Intersections Command
You can access it under the Ribbon menu Steel tab, Steel heading.
Click the divide-combine single intersections icon.
Select the purlin you want to split by clicking near its support.
The ideCAD will automatically split your chosen purlin.
You can combine previously divided purlins by clicking and selecting near the support.
You can set the distance between the purlin between the dividing process in the division on intersections section in the extensions tab of the Purlin Settings dialog.
Purlin before divide-combine single intersections command
Choosing the purlin to split
Purlin after divide-combine single intersections command