13 th International Brick and Block Masonry Conference Amsterdam, July 4-7, 2004 page 1 VULNERABILITY OF HISTORICAL CENTRES IN SEISMIC AREA: RELIABILITY OF ASSESSMENT METHODS FOR DIFFERENT BUILDING TYPOLOGIES C. Modena 1 , M.R. Valluzzi 2 , L. Binda 3 , G. Cardani 4 , A. Saisi 5 Abstract The application of simplified models for the limit analysis of existing masonry structures in seismic area is discussed in the paper. The procedure is mainly based on equilibrium conditions of macro-elements, involving kinematics mechanisms of structural components and assemblages. It allows evaluating the safety level of existing buildings in old centres according to the real conditions detectable in situ, often not satisfying the main hypothesis at the base of calculation methods designed and aimed at modern masonry structures (insufficient connections among components, presence of poor and non-homogeneous materials, lack of bond in the thickness of masonry wall, etc.). Different typologies of buildings located in three historic centres of the Umbria Region (Italy) are analyzed, characterized by various levels of damage. Key Words Seismic vulnerability, historic masonry buildings, macro-elements, improvement interventions. 1 Introduction The extensive in-situ surveys of some masonry buildings centres damaged during the 1997 Umbria-Marche earthquake in Italy pointed out the importance of a correct design and control of the execution of the repair interventions, based on the deep knowledge of the structure and its mechanical behaviour (Binda et al 1999, Penazzi et al 2000). Retrofitting after a previous earthquake, mainly performed with heavy interventions 1 Full Professor, Dept of Constr. and Transp. Eng., University of Padova, Italy, modena@caronte.dic.unipd.it 2 Assistant Professor, Dept of Constr. and Transp. Eng., University of Padova, Italy, valluzzi@caronte.dic.unipd.it 3 Full Professor, Dept of Struct. Eng., Polytechnic of Milan, Italy, binda@stru.polimi.it 4 Ph.D., Dept of Struct.Eng., Polytechnic of Milan, Italy, cardani@stru.polimi.it 5 Assistant Professor, Dept.of Struct.Eng.,Polytechnic of Milan,Italy, saisi@stru.polimi.it 1