Non-linear Methods for the Assessment of Seismic Vulnerability of Masonry Historical Buildings

The evaluation of seismic performance of existing masonry structures is a fundamental issue for the preservation of cultural heritage in general and of historical buildings in particular, even in view of the adoption of suitable policies for risk mitigation. To assess the seismic performance of existing masonry buildings, several refined push-over procedures for non-linear static analysis can be found in literature, mainly based on the equivalent frame approach. However, these procedures are not only very time consuming, but also very sensitive to modelling hypotheses, so that results could vary in a large interval even when users are very skilled. To solve these problems, the authors, aiming to enhance the classical pushover programs for masonry building, especially in terms of easiness of use, simplicity of modelling and computational demand, developed a reliable and sound push-over procedure allowing a quick evaluation of seismic risk index. The so called E-PUSH program, which allows the verification of multi-story masonry buildings according to the most recent structural codes and relies on very simple structural models, has been validated considering several relevant benchmark studies and comparing the results with classical procedures implemented in commercial programs. In the paper, a review of macro-element methods for the seismic assessment of unreinforced masonry buildings is then discussed considering the main hypothesis on masonry modelling, choice of masonry mechanical parameters and failure criteria and evaluating their impact on the estimation of seismic risk index. The results of the comparison will be finally presented and discussed for a relevant case study of a four story masonry building investigated by the authors in the framework of a research program agreement between the Municipality of Florence and the Department of Civil and Industrial Engineering of the University of Pisa.