Earthquake damage assessment of masonry churches: proposal for rapid and detailed forms and derivation of empirical vulnerability curves

The post-earthquake damage assessment represents the first step after an emergency to support not only the safety of people, but also the preservation of buildings through the realization of prompt and effective provisional interventions. The issue is of particular relevance in case of monumental assets such as churches that are the focus of the paper. In Italy, since 1997 the post-earthquake damage assessment of churches has been carried out using a specific form, which was formally approved in 2001 by the Italian Civil Protection. Being the most advanced tool available in the literature within this specific field, the Italian form has been widely used also internationally. It follows the approach based on the decomposition of the church into macroelements. Although the latter has found wide confirmation through the interpretation of real damage, some critical issues were raised in relation to the versatility of the form and the reliability of the damage index that the approach provides. The post-earthquake damage assessment of 48 unreinforced masonry churches located in New Zealand, hit by the Canterbury earthquake sequence 2010–2011, represented an unprecedented opportunity, at international level, to investigate and to address the aforementioned issues. Starting from some weaknesses of the actual form, a new proposal (named CAF-D) for the damage assessment of unreinforced masonry churches has been developed and presented in the paper. The new form is still based on the macroelement approach, but it considers, in a separate way, the macroelements and the seismic damage modes they might develop, thus overcoming the limitation of the fixed number of damage mechanisms identified a priori by the current Italian form. The more reliable damage assessment approach that such form aims to achieve is the prelude to the development of a specific vulnerability model, derived by combining an empirical and an expert elicitation approach. A specific vulnerability model developed for New Zealand churches, derived by implementing the proposed CAF-D form and the related damage assessment procedure, is presented in the last part of the paper