# Inspection and Structural Rehabilitation of an Existing Masonry Arch Railway Bridge
## 1 Introduction  
Existing masonry arch bridges are of great importance for road and rail networks and are also invaluable as they are part of architectural and cultural heritage. These ancient structures were designed many years ago according to semi-empirical rules based on a few simplified mechanical principles; however, their structural performance is exceptional in most cases [1]. However, at present, the safety and utilization of these existing bridges are in danger due to several factors. The performance deficit may be due to progressive damage from external actions, natural deterioration including material decay, structural inadequacy, events such as earthquakes, but also increased loads and vehicle speeds to which bridges originally designed for wagon passage are subjected. Therefore, a realistic and rigorous seismic structural assessment of masonry arch bridges is essential to preserve their functionality and cultural, economic, and strategic importance and vulnerability. It is necessary to carry out a seismic vulnerability analysis of these structures in order to upgrade them to the safety standard required by current codes if necessary. The relevance and effects of this problem are better highlighted if we consider the number of existing masonry arch bridges in the national and international territory that are used by the railway network. In Italy alone, there are about 56,000 of them, differentiated by arch type, number, and span length. Currently, there is a large body of literature analyzing the collapse of masonry arch bridges and masonry arches in general [2; 3; 4], reporting different structural models built according to different levels of accuracy and simplifications. In fact, the difficultyof representing the behavior of the resisting material and skeleton sometimes requires the use of a simplified but effective structural model suitable for the specific case. The methodologies developed can be based on limit analysis, nonlinear incremental techniques for two-dimensional arches, and Finite Element Models (FEMs) for three-dimensional arches, which allow both a complete description of the bridge geometry and detailed constitutive models.  
This paper falls within the field of engineering applications aimed at infrastructure engineering and proposes a methodology of analysis for seismic vulnerability assessment and suggests a valid and effective solution for the structural rehabilitation of an Italian masonry arch railway bridge. A structural analysis of the arch bridge under static and seismic actions in the current and future strengthened state was carried out on a three-dimensional FEM generated using Midas FEA NX software [5]. The detailed FE model is essential for conducting the nonlinear nonadaptive static analysis (pushover), which also takes into account uncertainties in the material properties and seismic input of the masonry arch bridge [6; 7]. Pushover analyses are common and widely used to evaluate global structure response and nonlinear collapse mechanisms because they are less complex than nonlinear dynamic analysis [8]. In fact, the latter is considerably computationally expensive and requires careful selection of seismic input data, since the results are strictly influenced by their choice.  
Therefore, this study shows a useful methodology of analysis for the seismic performance evaluation of an existing masonry arch bridge and proposes a viable structural rehabilitation solution by using traditional materials and techniques.