Fragility of single-span masonry arch bridges accounting for deterioration and damage effects

Masonry arch bridges, despite their age, are still fundamental structures in transport networks throughout Europe, especially for railways. Furthermore, these bridges are often found in seismic-prone areas, such as Italy. Developing of specific fragility models is of fundamental importance for large-scale seismic risk assessments of these structures and related transport networks. Unlike other types of bridges, for which significant progress has been made in assessing their seismic vulnerability and fragility, comparable results for masonry arch bridges are not fully available. Moreover, a realistic risk assessment of masonry bridges should account for deterioration and damage, which most of these bridges have developed being more than 100 years old and often in a poor state of maintenance. Therefore, this work intends to provide seismic fragility models for two generalised classes of single-span masonry arch bridges, i.e. segmental and semi-circular, taking into account their potential degradation through 2 D finite-element modelling and parametric nonlinear static analyses. Material loss from the intrados of the arch, material degradation, and longitudinal cracks on the arch barrel vault are investigated as typical defects. Overall, the seismic fragility of masonry bridges increases appreciably when the effects of degradation are considered, the loss of material being the most influential defect.