Analysis and assessment of the railway network facilities in Bulgaria. Solutions for their adaptation to modern operational requirements.

The present scientific work is devoted to the analysis and evaluation of the facilities on the railway network in Bulgaria, with a focus on the challenges related to their adaptation to modern operational requirements. The object of the study is the Sofia - Mezdra section of the railway line Sofia - Mezdra - Gorna Oryahovitsa - Varna. The selected section includes a wide range of infrastructure structures – bridges and tunnels - characterized by structural and material diversity, which makes it representative for the national railway network. A detailed technical survey and documentary description of the structures has been carried out, as well as an assessment of their current condition. Within the framework of the study, experimental tests of the main construction materials were also carried out in order to establish their residual service life. Special attention is paid to the old steel riveted bridges, for which specific engineering solutions are proposed for adaptation to the modern normative requirements, including those laid down in the Eurocode system. The presented approach combines practical measurements with a scientifically based methodology for assessment and strengthening, with a view to increasing the operational safety and extending the life cycle of railway structures in Bulgaria.