Abstract
Abstract. Seismic damage assessment is a valuable opportunity to evaluate the accuracy of vulnerability and risk methodologies applied to historic masonry buildings, giving the possibility of enhancing and optimizing mitigation and retrofit strategies. Vulnerability index methodologies are flexible and powerful tools for the seismic assessment at urban scale, able to provide a first screening of the critical issues present in masonry structural aggregates. The different structural features of the buildings, directly and indirectly influencing their structural behaviour, are measured through different weights and scores finally achieving a vulnerability indicator. In the present paper, four different vulnerability index methodologies are applied to the medieval city of Campi Alto di Norcia in Valnerina, Umbria, recently stroke by the 2016 Central Italy earthquakes. The accuracy of the adopted Iv methods is assessed based on the real damages’ analysis performed in the surrounding area, comparing results achieved from the application of considered methodologies to direct in-situ observations. Data collected during the 2016 post-earthquake damage surveys and usability assessment, together with the external visual inspections carried out and with the information coming from retrofitting design interventions performed between 1979 and 1997, are used.
Highlights
The historical building heritage is the result of an evolution interactive process, occurred over the centuries, between people and the surrounding area: the heterogeneous architecture often recognizable in old city centres is the expression of the cultural modifications, natural transformations and anthropic events.The masonry buildings constituting the urban environment are interconnected in Structural Aggregates (SAs) without following a well-organized development, and the construction typology changes according to the different places and realization periods (Giuffré, 1993)
The building heritage of Campi Alto di Norcia (Figure 1) covers an area of approximately 35,000 m2 with a perimeter of 750 m. 32 different structural aggregates can be identified within the area, globally resulting in 75 different structural units
The 43% of the buildings show a vulnerability index distributed between 40-50, 9% are between 50-60, 7% are between 60-70 and 12% are between 70-80
Summary
The historical building heritage is the result of an evolution interactive process, occurred over the centuries, between people and the surrounding area: the heterogeneous architecture often recognizable in old city centres is the expression of the cultural modifications, natural transformations and anthropic events. With the aim of simplifying this issue, a new methodology for the seismic risk assessment of structural aggregates is under development, starting from the deep analysis of pros and cons of existing methods and introducing innovative aspects coming from the direct observation of structural damages before and after seismic events. Thanks to the execution of past in-situ surveys assessing the structural condition of the SA before the seismic event and highlighting vulnerabilities, deficiencies and critical features, the direct observation of the consequences of the 2016 event allows to assess the accuracy of the considered methodologies in predicting the structural performance of the SUs constituting the SAs, evidencing deficiencies and issues of each applied method
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