A new numerical procedure for assessing the dynamic behaviour of ancient masonry towers

COMPDYN 2017
6 th ECCOMAS Thematic Conference on
Computational Methods in Structural Dynamics and Earthquake Engineering
M. Papadrakakis, M. Fragiadakis (eds.)
Rhodes Island, Greece, 15–17 June, 2017

The paper presents a new numerical procedure for the modal analysis of ma-
sonry structures implemented in the finite element code NOSA-ITACA, which models masonry
as a nonlinear elastic material with zero tensile strength and infinite or bounded compressive
strength. The procedure, which allows for taking into account the effects of the stress field
and crack distribution within a structure on its natural frequencies and mode shapes, is ap-
plied to assess the dynamic behaviour of a medieval bell tower in Lucca. Data recorded by
the monitoring system installed on the tower have been processed via suitable modal identifi-
cation algorithms, which have enabled calculating the tower’s modal frequencies, mode shapes
and damping ratios. Then, the tower has been analysed via the NOSA-ITACA code and model
updating techniques applied to fit the data measured on the tower. The results of the standard
modal analysis have been compared to those of modal analyses conducted on the structure
subjected to its own weight while taking into account the corresponding crack distribution.

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