Discrete Macro-Element structural assessment of a railway masonry arch bridge subjected to pier settlements

Settlements in bridges can induce structural damage that can be limited and affect only the serviceability of the infrastructure or, in the worst scenario, can cause local or global failure. To assess the structural behaviour of masonry arch bridge and identify the occurrence of damage, also in presence of structural health monitoring, reliable numerical models to perform sufficiently accurate nonlinear simulations are needed. The innovative strategy known as discrete macro-element model (DMEM) is here employed to assess the performance of a masonry arch bridge in presence of piers settlements. The adopted numerical strategy assures an easy and geometrically consistent model characterized by a low computational burden with very accurate results. The numerical investigation here reported is also devoted to detect the main structural parameters that have to be controlled in health monitoring bridge survey and to identify threshold levels to be considered for automatic early warning alerts. A masonry arch bridge located in Maletto (Italy), belonging to the rail network of Ferrovia Circumetnea (FCE), which was subjected to a retrofitting intervention due to the presence of extensive damage at the haunches of the arches, is here studied in its original configuration. A sensitivity analysis with respect to the settlement magnitude of a pier foundation is performed considering the operational loads by conducting nonlinear static analyses. The role of the settlements in masonry arch bridges and the relevant effects on the structural performance are shown and discussed also with the aim to associate the severity of damage to the structural performance of the bridge.