Seismic risk analysis of masonry buildings in aggregate: Fid-Bau Portal

Seismic risk analysis of masonry buildings in aggregate

Boschi, Sonia

The Italian territory is currently defined a total seismic area. The historical city centres in Italy consist mainly of load-masonry buildings in aggregate, composed by a group of structural units interacting each other. The vulnerability assessment of aggregates is a key aspect for the seismic risk mitigation: after recent seismic events, historical city centres showed several damages with implications of social and economic resources. The seismic risk is a function of three main aspects the hazard, the vulnerability and the exposure. There are different approaches for the vulnerability evaluation: empirical methods, analytical methods and a combination of them, the hybrid methods. In the first part of this work, after an overview of the state of art of the structural vulnerability assessment methods, the results of the application of an empirical approach will be illustrated. The method consists in the filling out of the “Aggregate Form”. The 74 masonry aggregates of Castelnuovo (L’Aquila), have been exploited as case study. Castelnuovo was hit by the earthquake of L’Aquila of 2009: most of aggregates have showed several damages. The vulnerability results allowed to build damage scenarios on Castelnuovo aggregates, varying macroseismic intensity of possible earthquakes and for the macroseismic intensity recorded in Castelnuovo. The application of this method helped to obtain information about the seismic behaviour of the aggregates and to determine the factors that mostly influenced their seismic behaviour. Analysing the distribution of the obtained Vulnerability Indexes and basing on the results of the predicted damage scenario, a new Vulnerability Aggregate Form has been introduced. Afterwards the attention has been paid on the detailed vunerability assessment methods. Based on the results of mechanical analyses done, and looking at the real damages experienced in Castelnuovo aggregates, out-of-plane mechanisms have been chosen as analysis type to study these structures. The local kinematic analysis have been applied to each façades. This procedure has allowed to understand which are the parameters that influence the seismic out-of-plane behaviours of façades, setting the basis for the definition of a new Form for Façades. This Façade Form, considering only geometrical information, allows an estimation of the capacity, expressed in terms peak ground acceleration and Safety Index considering the seismic hazard of the site in which the structure is built.