Évaluation de la vulnérabilité sismique des églises en maçonnerie non armée bâties selon le plan Conefroy

Abstract

Quebec is characterized by a moderate seismic hazard and previous earthquakes have demonstrated the high capacity of the ground to propagate the seismic waves. These two factors can result in significant damage to historic buildings, built mainly of stone masonry. Unreinforced masonry (URM) is a material known for its vulnerability to earthquakes, which has been observed during historical earthquakes in Quebec and around the world. The province is home to approximately 900 religious establishments (Québec, 2013). On the island of Montreal alone, 108 URM churches, built before 1945, have been identified through previous research. These structures are particularly vulnerable because of their slender walls with large openings. A review of the inventory regrouped the churches according to typology of the facade in order to study their structural vulnerability to earthquakes: the Neo-Romanesque, Baillargé, Conefroy, and Italian Baroque typologies. This dissertation focuses on the Conefroy typology, which is very present on the Quebec territory. The evaluation of the seismic vulnerability of this typology is carried out with a case study: the Sainte-Famille church in Boucherville. The study of the architectural and structural characteristics, as well as the few damages observed during past earthquakes, has shown similarities between churches in Quebec and those in Italy. This is why the study of vulnerability is carried out following the Italian methodology based on the principle of identification of macroelements and recognition of their failure mechanism following a survey of geometrical and structural characteristics. However, some specificities of Conefroy churches, such as the location of the bell tower or the structural characteristics of the roof, require to verify the applicability of the Italian methodology through complementary analyses in order to deepen the knowledge of the seismic behavior of these churches. 3D numerical models are built in order to understand the influence of each component on the building: the masonry walls, the bell tower and the roof. Modal analysis, calibrated on ambient vibration measurements, allowed to recognize the main failure mechanisms. The overturning of the gable of the façade and the side walls are the first modes of rupture obtained following these analyses. The comparison between the different 3D models has highlighted the increase in the rigidity of the façade when it is connected to the roof. On the other end, the roof did had a lower influence on the rigidity of the side walls of the church where a decrease of only 0.1 second was observed in the period. An interaction between the wooden bell tower and the URM façade is also observed in a way that they have the same mode shape. Finally, linear temporal analyses are applied to the models in order to evaluate the response of the church to an accelerogram of the 1988 Saguenay earthquake felt in Boucherville.

Date	18 Dec 2020
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Marie-José Nollet (Supervisor) & Maria Adelaide Parisi (Co-supervisor)