- Start with a 'Beams and Braces' family template. Call it space_truss
- Extrude main chords in right elevation and lock to ref planes.
- Extrude a solid in the same elevation and lock to ref planes. This will be web eventually.
- Start a new family based upon the 'Generic Model Faced Based' template. Call it space_truss_void
- Make a void which will cut out the desired space around the web. This will be one cell which we will array. Make sure you use 'Cut Geometry' on the voids and the host, even if they're not touching.
- Load the space_truss_void family into the space_truss family.
- Constrain and array the space_truss_void family along the member.
- Make an array parameter which distributes the space_truss_void family along the solid web.
- Load in to project and enjoy.