The form-finding / design process is iterative. The internal force distribution is being manipulated / altered by playing around with the graphical reciprocal force diagrams. This provides a high level of control to ‘shape’ and fine-tune the three-dimensional solution. The updated internal force distribution at each step is then used as a measure for the thickness of the vault: the vault becomes thicker where more forces accumulate (that’s the logic / strategy we chose). This added thickness has to be accounted for in the loads applied in the nodes and the program runs again to find the updated equilibrium shape.
This piped solution gives a good idea of the sculptural qualities of the thickening along the main force lines in the network. These ribs will also help stiffen the vault, which becomes very important under asymmetric loading conditions.