PSI - Issue 84

S. Lorefice et al. / Procedia Structural Integrity 84 (2026) 669 – 676

670

Keywords: modelling, analysis, bridges, structures, steel, reinforcements

1 Introduction The case study examined concerns a railway infrastructure consisting of two approach viaducts arch bridge connected by an under truss steel bridge. The lateral viaducts, of multi-span arch type, comprise three and six spans, respectively. The aim of the study is the strengthening and upgrading of the entire infrastructure, with the objective of increasing both global and local structural safety levels. The safety assessment was carried out through structural analyses and performance checks of the structure in its as-built condition (ante operam), which enabled the identification and definition of the necessary strengthening interventions. Subsequently, verification analyses were performed for the design configuration (post operam), also accounting for the replacement of the existing steel deck with a newly designed one, in order to ensure compliance with current regulatory and performance requirements. 2 Structure general description The infrastructure consists of a railway viaduct with an overall length of approximately 200 m, comprising ten spans, located along a single-track railway line crossing the Lamone River.

Fig. 1. Overview of the bridge in the as-built condition: left—masonry arches and steel girder; right—concrete arches

The existing steel structure is a girder with an upper-track configuration with a span of approximately 54 m, composed of main lattice girders arranged in a multiple-truss configuration. The arched approach viaducts consist of a three-span bridge and a six-span bridge. The three-span viaduct is characterized by arch barrel constructed in solid brick masonry, whereas the six-span viaduct features concrete arches. All arches are semicircular, with a clear span of approximately 11.50 m. The spandrel fill consists of cyclopean concrete, which also forms the core of the piers and abutments . The substructures are faced with solid brick masonry, with thicknesses ranging between approximately 30 cm and 50 cm. Similarly, the spandrel walls are constructed of solid brick masonry, with an average thickness of approximately 50 cm . 3 Historical and critical analysis The infrastructure under investigation, dating back to the late nineteenth century, is characterized by significant historical value. It is part of the so-called Faentina Railway , a strategic railway line of that period, which played a fundamental role in connecting Tuscany and Romagna. The arches of the six-span bridge were originally constructed in masonry; however, they were destroyed during World War II as a result of wartime events and subsequently reconstructed in concrete.

Fig. 2. Left: load testing of the steel structure (1892) – Right: six-span bridge with concrete arches (1961)