Innovative probabilistic methodologies to assess seismic vulnerability of simple supported girder bridges

Since the end of the eighties, numerous studies have been conducted analysing the relationship between the infrastructures and the economic development of the territory, highlighting its close correlation. In the last decades, the costs for the management and maintenance of these networks have increased considerably considering the age of the same and the increase in demand that has been witnessed. The phenomenon is particularly evident in some elements of transport networks such as bridges, viaducts and tunnels, which, as evidenced by the telluric events that have hit Italy in recent decades, have shown a high level of vulnerability also towards media events. Intensity. The problems encountered are essential because the Italian infrastructural network is constituted for the vast majority of bridges built in the 60s and 80s, structures conceived in seismic territories generally only afterwards and, therefore, without seismic engineering criteria. Furthermore, the lack of routine maintenance policies and practices has accentuated the decay of structural services in some cases. This thesis study focuses on the analysis of the efficiency of adaptation and improvement techniques for multi-span bridges simply supported, built in Italy in the 60s-80s, a simple bridge/viaduct suite was used. Defined according to the geometric and mechanical characteristics detected by the bridges built on the Italian motorway and road network. To evaluate the structural performance of bridges and viaducts, the probabilistic method from the basis of Performance Based Earthquake Engineering (PBEE) was used, in particular through the use of fragility curves. The purpose of bridging curves for bridges, however, shows some limitations, since they are complex structures composed of several structural elements that interact with each other, so it is difficult to determine the collapse mechanisms of the whole system. To simplify the comprehension of the global collapse mechanism, thus facilitating the general evaluation of the improvement proposals related to the single structural components, we propose an innovative method of analysis and graphic representation of the fragility curves. [edited by Author]