Modal Analyses on the Lateral Resistance System of the Auxerre Cathedral

One of the unique characteristics of the French Gothic is the use of flying buttresses over the side aisles to support the thrust of the nave vaults. It can also be hypothesized that the medieval master masons must have used these buttresses liberally for lateral resistance against external forces such as high winds. Moreover, there is an increasing interest on the seismic resistance of historical buildings in Europe, which emphasizes further the need to better understand the lateral capacity and dynamic behavior of Gothic structures. In this study, a finite element model of the transverse frame of the Auxerre cathedral in France is developed, and analyzed under lateral loads with and without the flying buttresses to observe the difference in behavior. The dynamic behavior of this finite element model, which is developed with previously validated material properties, is compared to hand-calculated modal analysis of a simplified frame with multiple beam elements. This is a research in progress with objectives of better understanding the design considerations behind the use of flying buttresses, and developing an accurate and practical method for analyzing the dynamic behavior of Gothic structures.