Open issues on seismic assessment of existing masonry buildings: linear vs nonlinear, static vs dynamic, local vs global approaches

ABSTRACT: The seismic assessment of existing masonry buildings is a difficult task due to the complexity of reliable models, particularly in the case of older non-engineered ones. The qualitative approach is a essential element of knowledge for the interpretation of the seismic behaviour but cannot replace a quantitative security check. As-built information, based on historical notes on transformation and the survey of constructive details, together with the results of investigation on material properties, are the basis for the choice and calibration of the structural models with which to carry out the verifications. Modelling and analysis procedures should be as accurate as possible in catching the actual seismic response, but at the same time robust and practice-oriented. This keynote lecture offers a general framework for the assessment of existing masonry buildings (in unreinforced, reinforced and confined masonry) and is focused on distinctive features and open issues in this field. The assessment is based on the evaluation of the global seismic response, relying on the in-plane resistance of masonry walls, and the verification of possible local mechanisms, related to out-of-plane behaviour of walls substructures. For the global analysis, it is suggested: a) a modelling approach that takes into account the diaphragms stiffness; b) different failure criteria for masonry piers for regular and irregular masonry; c) specific failure criteria for the spandrels; d) a combination of global and local checks for the definition of limit states. For local mechanisms, the following are proposed: a) the use of equilibrium limit analysis, considering the evolution of rigid block mechanisms, for the evaluation of the horizontal seismic strength and the ultimate displacement capacity; b) a new formulation for the floor spectra, with an accurate estimate of the displacement demand on these mechanisms at different levels of the building.

Bio : Sergio Lagomarsino is professor of Structural Engineering at the University of Genoa, since 2000. Author of many journals papers and chapters of scientific books on the topics: seismic assessment of existing structures, nonlinear modelling of masonry, preservation of monumental buildings and historical centres, seismic risk and vulnerability analysis (in Scopus: h-index 24, 78 articles and 1791 citations). He has coordinated the European project PERPETUATE on the seismic assessment and protection of cultural heritage assets, as well as many other national projects. He sits on the editorial boards of “International Journal of Architectural Heritage" and of “Earthquakes and Structures”. He has served in the drafting panels of the Italian seismic code and the Italian Guidelines for cultural heritage in seismic areas. At present, he is member of the Project Team 3 that is working on the revision of Eurocode 8, Part 3: “Assessment and retrofitting of buildings”. He developed the software program TREMURI, for the nonlinear seismic analysis of masonry buildings, and the Italian survey form for post-earthquake damage assessment of churches.