Seismic Vulnerability Assessment of Unreinforced Masonry Churches in Central Chile

During the 2010 Maule earthquake (Mw 8.8), extensive structural damages afflicted the Chilean Built Heritage, and in particular, the unreinforced masonry (URM) churches, which highlight the importance of implementing effective retrofit and repair techniques after the frequent severe seismic events in the country. These religious structures exhibit profound typological and constructive peculiarities, derived from the combination of constructive characters of European architectural revivalisms (declined mainly in Neo-classic and Neo-gothic), of Colonial architecture and of mixed constructive culture. The building techniques and materials are a very heterogeneous set, characterized by different building techniques and materials. The peculiarity of this heritage and the seismic exposure of Chilean territory motivate the need of defining a systematic method to assess the seismic vulnerability of the Chilean unreinforced masonry churches. Firstly, a complete database was generated with the geometrical, constructive, and structural characteristics of a representative stock of 106 URM churches of central Chile (the Santiago de Chile Metropolitan Region and the Libertador General Bernardo O'Higgins Region). Then, the damage index for each church was analyzed in terms of its failures affecting the sub-assemblages of the structure with independent behavior and quantified through a macro-seismic method, taking into account a new set of collapses mechanisms, specifically arranged for Chilean churches. Finally, the results of the damage index method are employed to obtain damage probability matrixes and empirical fragility curves. The derived fragility curves are directly usable in a risk assessment framework, which is commonly used by stakeholders or safety decision-makers.