PSI - Issue 62

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Mattia Zizi et al. / Procedia Structural Integrity 62 (2024) 430–437 M. Zizi et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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considered due to the presence of concrete elements and road pavement at the road level. In Fig. 7, a view of the adopted numerical model is provided.

Fig. 7. The adopted numerical model (regular tuff elements in grey and backfill elements in green)

4.2. Numerical analysis results Modal analysis was performed and the numerical results compared against the experimental ones. Both mode shapes and frequencies obtained from the adopted numerical model were quite similar to the ones obtained with the dynamical characterization, despite the roughness of the model and the strong simplifications about the mechanical characteristics of the materials. Three bending modes were returned by the modal analysis at 1.52 Hz, 2.46 Hz and 3.91 Hz. The numerical model exhibited also a mode at 3.71 Hz having a mainly longitudinal mode shape, which was not identified experimentally. In this sense, it cannot be excluded that given the experimental conditions, the dynamical characterization was not able to capture such a mode. Moreover, at 4.95 Hz the numerical model returned a vertical mode. The numerical mode shapes are shown in Fig. 8 and by comparing them with the ones shown in Fig. 6 a satisfactory consistency can be appreciated.

Fig. 8. Numerical modes (perspective view): (a) at 1.52 Hz, (b) at 2.46 Hz, (c) at 3.91 Hz and (d) at 4.96 Hz.

5. Conclusions The present study dealt with a five-span masonry arch bridge in Province of Caserta. In particular, the results herein proposed must be considered preliminary and part of a wider research activity concerning the structural and seismic safety of such structural typology. An accurate survey of the bridge, mainly based on aerial photogrammetry, was performed allowing for the creation of a reliable geometrical model. Then, the dynamic behavior of the bridge was defined thanks to a dynamical characterization performed under both environmental and anthropic (i.e. traffic) input. Such a characterization allowed for clearly identifying four main vibrational frequencies and mode shapes.