ABSTRACT
This chapter aims to assess the suitability of the addition of the medieval flying buttresses to the basilica of Vezelay. It explores the structural behavior of the nave before the construction of the external flying buttresses is discussed on the basis of two different approaches: thrust line analysis and Discrete Element modelling. The history of the basilica is also the history of its structural problems. The stability of the basilica can be quantified in terms of a geometrical safety factor. The thrust line analyses indicate that the basilica without the flying buttresses was quite close to its stability limit. The safety of the basilica is even lower than the estimated values given in the thrust line analysis. The amount of wall that contributes to the stability of the buttress depends on the quality of the construction and the joining between the wall and the buttress.
