PSI - Issue 44

Mattia Zizi et al. / Procedia Structural Integrity 44 (2023) 673–680 Mattia Zizi et al. / Structural Integrity Procedia 00 (2022) 000–000

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The analyses showed that by improving mechanical properties of backfill material, significant enhancement in the seismic response of the bridge could be obtained. This is particularly evident in the cases of Elastic Modulus and cohesion increments. As a matter of fact, increments of the bridge's capacity up to 20% and 30% were obtained with the highest values assumed for E b and c , respectively. Conversely, the overall capacity seems only slightly influenced by variations in friction angle of soil or at the interface between backfill and masonry. The force-displacement curves of the analyses are shown in Fig. 8.

Fig. 8. Results of the parametric analysis by varying: (a) Elastic Modulus of backfill, (b) cohesion of backfill, (c) friction of contact and, and (d) friction angle of backfill.

As a first conclusion, it can be thus admitted that, for example, an intervention aimed at strengthening and stiffening the backfill could represent an effective enhancement intervention for such types of structures. Another aspect that should be mentioned is that, given the small height of the piers, probably such technique can be considered particularly suitable for cases similar to the analyzed one, where the response is mainly governed by the arched system rather than the substructures. Moreover, the transversal behavior has not been investigated since in the reference case no spandrel walls were considered. In the case of transversal seismic forces, the collapse of the bridge may significantly depend on the out-of-plane mechanisms of these elements, which would require specific retrofitting actions to guarantee a monolithic behavior of the structure, e.g., by means of transversal tie rods. 4. Conclusions and future developments In the current study the seismic response of a masonry arch bridge was investigated by means of 3D nonlinear FE models. A reference model was calibrated based on the evidence obtained in an experimental test from the literature. The calibrated model allowed for assessing the longitudinal seismic response of the bridge. Since past literature studies widely demonstrated that the backfill material could play a dominant role in the response of masonry arch bridges, parametric analyses have been performed in order to estimate the influence of its mechanical parameters on the global response, as well as to identify possible solutions for enhancement interventions. On the whole, it has been noted that a significant improvement of the seismic capacity could be potentially achieved by stiffening and strengthening the backfill, without acting on the resisting masonry parts. Such an intervention typology could also guarantee a certain beneficial cohesion to the backfill material. However, it must be specified