"Transverse section of Notre-Dame de Paris before the 2019 fire. Timber framework in red, masonry in blues, metal in grey. Center, nave, covered by masonry vault and 55-degree triangular roof (spire shown above and behind). Flanking the nave, side aisles, triforium aisle above, flying buttresses. Note that the vaults thrust outwards on the walls, and the flying buttresses thrust inwards; unless these two forces balance, the wall will be pushed over. Black arrows show the force of the weight of the structure being transmitted to the ground; green arrows show the upwards force of the ground supporting the structure. Orange arrows show the forces in the wood of the roof trusses. Roof trusses cancel out their outwards forces using internal tension (masonry cannot support tension). Light added for clarity."
Courtesy of HLHJ.
Creative Commons (BY-SA).
