A = Area
x = Distance from neutral axis to farthest fibre
I = Moment of Inertia
S = Section Modulus
r = Radius of gyration
This creates a simple cylinder or “rod” with the central axis aligned along the quad-edge. To account for hubs, you can specify the hub radius in the ‘Strut Options’ where you can also specify the strut ingress distance – i.e., what portion of the strut is clamped, fixed or inserted within the hub.
The screenshot below demonstrates the result. The hubs are not shown and the shortening has been exagerated for clarity. All struts are shortened by the same amount, which is:
[hub radius - strut ingress distance] * 2.0
The strut width has been deliberatelty increased to show the geometry.
CAVEAT. If you do not account for the hub size, and simply keep the cylinders the same lengths as the original quad-edges, then the envelope will increase in size after construction. On the other hand, if you account for hub size, and shorten the cylinders accordinly, then the extents entered in the ‘Envelopes’ window will remain constant, and the base of the dome will not overshoot its foundations.