Operational Modal Analysis on an Emblematic Brick Masonry Historical Building in Latin America: The Case of the Lima Metropolitan Cathedral

Due to heritage buildings’ historic and social relevance, their structural diagnosis and restoration must be carried out according to modern conservation philosophies. In this regard, Operational Modal Analysis (OMA) constitutes a widely used non-destructive testing that allows the identification of a structure's dynamic properties (natural frequencies, mode shapes, and damping ratios) by measuring ambient vibrations as an excitation source. These properties not only provide a reliable estimation of the behavior of the building according to its current conservation state, but they also allow the identification of structural damage. In Peru, earthquakes are the major hazard for preserving historical constructions. This investigation focuses on applying OMA to the Lima Metropolitan Cathedral, a complex brick masonry and timber structure, to identify its dynamic response in operational conditions. The dynamic identification was carried out considering two stages: the first focusing on the bell towers and the second on the entire structure. Six and four vibration modes with their corresponding natural frequencies were identified for the local (bell towers) and global responses of the structure, respectively.