1 Department of Civil Engineering, Université de Sherbrooke, Sherbrooke, QC, J1K 2R1, Canada, jean.proulx@usherbrooke.ca
2 Department of Construction Engineering, École de technologie supérieure, Montréal QC, H3C 1K3, Canada, marie-jose.nollet@etsmtl.ca
3 Department of Civil Engineering and Applied Mechanics, McGill University, Montréal QC, H3A 0C3, ghyslaine.mcclure@mcgill.ca
ABSTRACT
This paper presents an ongoing collaborative research program on the dynamic characterization of unreinforced masonry (URM) buildings, which typically comprise steel or reinforced concrete framing systems with nominal ductility and URM infill walls. Past earthquakes, most notably the 1988 Saguenay earthquake for eastern Canada, have shown the hazards associated with the seismic performance of URM. This material is commonly found in high importance structures such as schools and hospitals built in the first half of the 20th century before the introduction of any seismic provisions in the National Building Code of Canada (NBCC) and structural design codes. Retrofitting programs for these structures rely both on the evaluation of their seismic capacity and a realistic estimation of the seismic demand. However, the equations of the NBCC for estimating the fundamental period of URM buildings neglect the contribution of the infill walls. Infills increase the lateral stiffness of the building and as a result decrease its fundamental period, resulting in underestimated seismic loads. This research is part of an initiative to establish a database on the seismic vulnerability and dynamic characteristics of existing URM buildings. Ambient vibration tests were carried out by three research groups (Sherbrooke, ETS, McGill) on school buildings in different areas of the province of Quebec. This paper focuses on a particular sample of reinforced concrete frames with infill walls. It is hoped that the dynamic properties collected will contribute to the determination of more precise formulas for the fundamental vibration periods of such buildings in view of seismic demand estimations for URM seismic rehabilitation projects or new building constructions using masonry walls.
KEYWORDS: structural dynamics, seismic design, unreinforced masonry, ambient vibration, fundamental period, natural frequency
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