SEISMIC VULNERABILITY ANALYSES OF MASONRY AGGREGATE BUILDINGS IN THE HISTORICAL CENTRE OF SULMONA (ITALY)

The limit analysis approach applied to structural macro-elements that can develop in historical masonry buildings under seismic action, depending on few geometric and mechanical parameters, allows reliable expeditious vulnerability assessments. Vulnus is an automatic procedure developed at the University of Padova and based on numerical models calculating the accelerations which activate local collapse mechanisms of macro-elements: the methodology provides, through a knowledge based fuzzy model, vulnerability assessments of individual structural units or groups of buildings, as well as fragility curves related to the achievement or overcoming of the limit state of heavy damage. Moreover, Vulnus is able to identify the vulnerability class for each structural unit, as defined by the European Macroseismic Scale EMS98, allowing the construction of damage scenarios. The EMS98 scale separates the definitions of building typologies from the corresponding vulnerability class and thus from the expected behaviour in case of seismic event: in this way, it provides a common framework for the evaluation of seismic vulnerability and the estimation of the damage of buildings on a large scale. The results of analytical applications of the procedure on buildings aggregates sampled in the historic centre of Sulmona, in L’Aquila province, an important historic centre in Central Italy, are presented. It is an area of great interest, not only considering its seismic history, but also because of the characteristics of its prestigious buildings, mainly made of poor multiple leaf stone masonry. Preliminarily, an on-site investigation methodology, based on the buildings survey using specific forms, the collection of data on interventions, damage mechanisms, etc. and a minimum number of laboratory and in-situ tests, was applied in order to collect all the data requested by Vulnus and to provide useful indications on the actual vulnerability conditions of the centre to be compared with the results obtained with the automatic procedure. In fact, the knowledge of typology and damage of historic masonry structures in seismic area is fundamental for the choice of suitable techniques and materials aimed to the preservation and damage prevention of the cultural heritage. The paper describes this procedure, addressed to an articulated knowledge of the material, of the morphology and of the constructive aspects of the masonry structures, of the mechanical behaviour and of the possible failure mechanisms of complex buildings in Sulmona (AQ). The understanding of the historical buildings has made use of a direct survey of the constructions (based on a geometrical survey, on a survey of the materials and of their state of damage), of indirect information deduced by documentary sources, and of data collected through in-situ non destructive or minor destructive testing and laboratory investigation for a chemical, physical and mechanical characterisation of the masonry and of its components.