Jimmy-Lee Mc Lellan, Rola Assi and Jean-Philippe Ouellette
i Master student, École de technologie supérieure (ÉTS), Montreal, Canada, jimmy-lee.mclellan.1@ens.etsmtl.ca
ii Associate Professor, École de technologie supérieure (ÉTS), Montreal, Canada, rola.assi@etsmtl.ca
iii Co-research director, Cosigma inc., Montreal, Canada, jean-philippe.ouellette@cosigma.ca
ABSTRACT
While unreinforced masonry (URM) is prevalent in Quebec’s cultural and religious heritage, very few practical and simplified methods are available to predict its behavior when subjected to dynamic loading (such as the sounding of the bells), and seismic events. Through a case study of the Notre-Dame Basilica of Montreal (NDB), the dynamic behavior and stresses within the unreinforced masonry bell towers resulting from vibrational forces were assessed using a reliable numerical model developed and calibrated with ambient vibration measurements (AVM). AVMs were acquired using Tromino® in both towers to obtain their dynamic behavior under 3 conditions: i. ambient solicitations without bell ringing; ii. the influence of bell ringing: a carillon with multiple bells for the East tower and a single bourdon for the West tower; iii. the influence of the bell ringing from both towers simultaneously. To complement the dynamic characterization, the bells were also modeled to assess potential resonance with the towers’ structural modes and to isolate their vibration effects from the global response. Subsequently, the recorded signals were processed in the modal operational analysis software ARTeMIS® to obtain the tower’s modal properties. Finally, a global finite element model comprising both towers and the narthex façade was constructed using the SAP2000® software and was calibrated using the AVM results. After calibrating the model to the first three fundamental vibration modes, the discrepancies between the initial model and the experimental results obtained through the AVMs were reduced by 52.9%, 23.5%, and 5.3%, respectively, for each mode. The calibration and the modeling process provide a deeper and more realistic understanding of the dynamic behavior of unreinforced masonry bell towers, enabling an accurate assessment of internal stresses and the identification of vulnerable locations in terms of structural integrity.
KEYWORDS: Dynamic analysis, unreinforced masonry (URM), churches, ambient vibration measurements (AVM), modal analysis, finite element model, Notre-Dame Basilica of Montreal (NDB).
129-McLellan.pdf
