PSI - Issue 44

Paolo Zampieri et al. / Procedia Structural Integrity 44 (2023) 926–933 Zampieri et al./ Structural Integrity Procedia 00 (2022) 000–000

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1. Introduction Italian railways network, largely built between the second half of 19th century up to the half of the 20th century, includes a large number of bridges and viaducts with an average age of approximatively 100 years.The developments of the technical international standards that have defined highest levels of safety, the absence of the seismic actions in the design phase as it is reported in Manzini et al. (2020), the increased traffic loads and the degradation of bridges are the main reasons for planning the maintenance and reinforcement of masonry bridges by railway infrastructure managers. The adoption of restrictive measurements (for examples speed and/or load reductions, circulation interruptions) involves economic losses, users inconvenience and severe disruption to rail traffic; for these reasons bridges interventions that keep in service the railway lines are generally preferred. Especially referring to masonry arch bridges, strengthening interventions in the arch are preferred. In addition, the use of FRCM (Fiber Reinforced Cementitious Matrix) composite materials could be a valuable alternative to the traditional strengthening techniques (Iacobini et al (2020)) and to the use of FRP (Fiber Reinforced Polymers) composite material (Simoncello et al (2020)). The application of one or more layers of the FRCM reinforcements to the arch intrados (Zampieri (2020) and Zampieri et al. (2020)) increases the structure capacity by delaying the opening of the hinges. Moreover, it doesn’t significantly change the geometry and the stiffness of the structure and thanks to the mortar matrix it matches better with historical masonry compared to the FRP reinforcements.This paper describes the preliminary experimental results obtained from destructive cyclic tests on masonry arches strengthened with a single layer of FRCM reinforcement applied to the arch intrados and compared with tests performed on unstrengthened ones. 2. Masonry arch specimens The destructive tests, subject of this document, were performed on masonry arch specimens with a span (s) of around 3 m, arch rise (r) of 1.32 m and arch thickness (t) of 0.25 m. The barrel vault has cylindrical intrados, rectangular plan and transversal section of 0.51m x 0.25m. The arch specimen provides solid bricks with regular texture and mortar joints (Fig. 1). Furthermore, in order to simulate the structural characteristics of the Italian existing railway bridges, the haunching is characterized by poor mechanical properties, using the mortar introduced above. Tests were performed to measure the strength of the CFRCM (Carbon Fiber Cementitious Matrix) strengthening system applied to the intrados of the arch. One test was performed on an unreinforced arch and the other on the same specimen strengthened with the CFRCM system. The strengthening system consists in a bidirectional carbon grid characterized by a weight density of 200 g/m 2 embedded in a mortar with pozzolanic reaction. Carbon connectors were used in order to increase the coupled behaviour between the arch intrados and the FRCM layers.