Octagon Solution to Cross Vaults Lateral Trusts
The geometric solution starts with the plant octagon and the structures defined thus far, folio 118:01.
The plant octagon minor diagonals connect the tower outer corners E passing through the corners B or H where the tower are attached to the façade wall, folio 118:02.
The web of minor diagonals inside the plant octagon defines a number of intersections. The minor diagonal intersections close to the façade wall are at right angle, folio 118:03.
These intersections meet the right-angle requirement for a square cross vault.
The right angle intersections of the minor diagonals are adopted as the square vault diagonals, folio 118:04.
The lateral trusts from such square cross vaults flow away from these intersections along the minor diagonals, folio 118:05.
The full set of lateral thrusts are lined up along the minor diagonals and terminate at the plant octagon corners where towers are located, folio 118:06.
Towers, whose volume is 90% masonry, are the piers that ultimately provide abutment to all lateral thrusts.
Masonry struts are needed along the minor diagonals between cross vaults and towers, folio 118:07.
Masonry struts are also need along the minor diagonals between cross vaults, folio 118:08.
A straight line of masonry has to be established between towers along minor diagonals for the proper discharge of lateral thrusts to the tower piers, except of course for the cross vault spaces, folio 118:09.
The struts between cross vaults and towers are in the space area already populated by the façade wall masonry, folio 118:10.
The insides masonry struts form the core of the courtyard wall. They define the location of this wall, but not its dimension or the location of its faces.
The resolution of the cross vault lateral thrusts defines the location of the cross vaults, which is the intersection of the plant octagon minor diagonals, folio 118:11.