SEISMIC VULNERABILTY ASSESSMENT OF ISRAELI HISTORICAL CENTRES

The configuration of historical centres is often complex and consequence of centu-ries of modifications. Clustered buildings which compose them are vulnerable, in particular against seismic action. The knowledge of their structural behaviour is fundamental in order to define prevention strategies and to reduce seismic risk. This paper refers to vulnerability as-sessment of the historical city centres of Safed and Acre, in the North of Israel. The methodol-ogy adopted is based on a preliminary knowledge phase. It is focused on the analysis of the seismic activity of the area and its urban and environmental context. Safed stands on a slope with more than ten metres of anthropogenic strata vulnerable to landslides. The town is de-veloped on the contour lines and as a consequence basements and underground vaulted sto-ries are recurring. Vice versa Acre is located on the Mediterranean coast and present continuous stratifications taken place during the centuries as a consequence of historical events. The study is carried out analysing some representative selected blocks. Considering the aim of an urban seismic assessment, specific survey forms are rearranged in order to col-lect buildings geometrical – typological data and information about vulnerability, exposition and damage. These are statistically analysed and allow to identify recurring typologies. For a global simplified analysis automatic procedures are implemented for each structural unit or group of them, obtaining a linguistic vulnerability assessment and fragility curves. Clustered buildings often do not show a global behaviour while they respond to seismic action as a group of local mechanism of collapse: local out of plane mechanisms are analysed, consider-ing both the survey and the typological data. Comparing all the obtained results, it is possible to appoint a vulnerability assessment and classification. In addition, the aim of this approach is to chart the results to other quarters of the historical centre: using the survey forms it is possible to identify structural units and to assign them the correspondent typologies previous-ly identified and the related vulnerability assessment.