Issue 60

F. Greco et alii, Frattura ed Integrità Strutturale, 60 (2022) 464-487; DOI: 10.3221/IGF-ESIS.60.32

Figure 16: Comparison between the seismic indicators for the pre-assigned failure mechanism of the bell tower.

Figure 17: Number of structural elements requiring retrofitting interventions as a function of the required seismic upgrade level, for masonry elements (A) and reinforced concrete elements (B). In order to obtain a more precise information about the seismic vulnerability of the Cathedral, the numerical results arising from the nonlinear static analysis performed on the structural macro-element are considered. In particular, the curve that provides the most conservative results in terms of collapse displacement has been chosen among the three curves depicted in Fig. 12(A), with the aim of deriving the related seismic vulnerability indicator. After the evaluation of the capacity curve of the structure, that represents the structural response of a multi-degree-of-freedom (MDOF) system [56], the curve of the single-degree-of-freedom (SDOF) system has been evaluated by dividing the horizontal displacement and base shear, i.e. the coordinates of each evaluation point, by the modal participation factor of the given macro-element evaluated during a preliminary linear dynamic analysis. Moreover, the equivalent bilinear curve needed for the evaluation of the seismic indicator has been also evaluated, as show in Fig. 18.

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