The role of the Modal Assurance Criterion in the interpretation and validation of models for seismic analysis of architectural complexes.

The seismic vulnerability assessment of historical buildings is usually a very complex task because of the large number of uncertainties in the characterization of their structural behaviour. The unique structural configurations, the adoption of old construction techniques and the presence of stratified structural modifications occurred over the centuries make the definition of an appropriate and reliable numerical model very challenging. The available analysis approaches distinguish the local response of selected macro elements from the global response of the structure. The problem of discriminating if the investigated structure shows a global behaviour or a local response has been often reported in the literature. However, the definition of a quantitative measure to discriminate the global modes from the local ones and, in the latter case, the associated macro elements, is currently missing. The Modal Assurance Criterion is a vector correlation index frequently used in experimental dynamics to quantify the similarity of mode shapes. In the present paper, it is used to define an original and quantitative approach to the discrimination between local and global modes. Results of application of the proposed procedure to an explanatory case study are reported, pointing out how the proposed method can guide towards the selection of the most appropriate analysis method. [ABSTRACT FROM AUTHOR]