Location
Cassino (Frosinone) Italy
Year
2023 / 2024
Client
RFI - FS Group
Dimensions
14,61 ml (SPAN) - 4 ml (WIDTH)
Introduction and Historical Background
The structure in question is a twin-girder bridge located at km marker 137+637 on the double-track Rome–Cassino railway line, within the municipality of Cassino.
The bridge is situated in close proximity to Cassino station and spans the Gari River, near the Terme Varroniane park.
The existing railway bridge consists of a metal twin-girder span with a clear span of 15.5 m, while the orthogonal distance between the abutments measures 15.31 m.
Geographically, the territory of Cassino occupies a strategic position along the two main routes connecting Rome and Naples, linked by key transport infrastructures. In 1892, it became part of the first railway line between the Italian capital and the Campanian capital, featuring two stations—one in the city center and another named Fontanarosa. In the 1960s, the new A1 motorway was constructed parallel to the old Via Casilina. Today, Cassino represents a significant urban hub, serving as an important center of attraction for the entire Province of Frosinone.
An internal archive review revealed an as-built drawing of the steel-span bridge over the Gari River at km 137+637 on the Rome–Cassino line, dated back to December 1973. The existing deck comprises two twin spans, each formed by four 1.00 m high double-T beams. The structure is laterally braced with L-shaped diagonals and cross braces made from additional double-T profiles. An internal archive review revealed an as-built drawing of the steel-span bridge over the Gari River at km 137+637 on the Rome–Cassino line, dated December 1973. Due to deterioration identified during client inspections, replacement of the spans was mandated.
Design
Demolition
Construction
Structural and technical testing
Design
The bridge’s location, in an area of strategic importance both infrastructurally and environmentally, presents complex design challenges. The Gari River is an ecologically and historically significant watercourse, situated near a site of notable scenic and cultural value, including its proximity to Cassino railway station. This context makes the replacement project not only an engineering endeavour but also an opportunity that must account for multiple considerations: hydraulic safety, environmental sustainability, and integration with the urban and historical context of Cassino.
One of the main design challenges for the new bridge was the presence of the Gari River and the need to construct deep foundations within the riverbed while keeping railway traffic active throughout the construction period, without the impact on the delicate environmental and landscape balance. The chosen construction techniques included the use of eco-friendly materials and sustainable waste management throughout all phases of the project.
To minimize interference with the natural river course, partial diversion of the Gari River was necessary. During the foundation and superstructure works, the river was temporarily redirected to allow construction without compromising its natural flow. This was achieved using temporary barriers made of sand-filled eco-friendly cofferdams, which allowed a portion of the river to continue flowing while ensuring the safety of the construction site.
Additionally, drainage and filtration systems were designed to prevent contamination of the river during construction activities in order to safeguard water quality.
During the in-river works for the construction of the deep foundations and the new railway bridge structure, a continuous environmental monitoring program was implemented, with particular focus on the water quality of the Gari River. This monitoring was essential to ensure that construction activities did not adversely affect the river’s ecosystem and to maintain the natural flow of the watercourse (albeit partially diverted) throughout the intervention phases. Water quality was assessed through periodic analyses of samples taken from the Gari River at various strategic points, both upstream and downstream of the construction site.
The analyses focused on key physico-chemical parameters, including:
· Water temperature
· pH levels
· Dissolved oxygen concentration
· Turbidity
· Heavy metal concentration
· Presence of organic contaminants
Overall, the monitoring results confirmed that the in-river operations were carried out in compliance with environmental regulation, having minimal impact on the watercourse. The protection of the fluvial ecosystem was ensured by adherence to containment measures, careful management of the river diversion as well as spatialisation operations. This helped maintain the health of the Gari River throughout all phases of the work.
Installation of the new steel spans
The final phase of the project involved the installation of the new steel caissons, a complex operation executed with precision to minimize disruption at Cassino station. The removal of the old spans and the placement of the new elements were carried out during a scheduled 144-hour rail line closure, of which 88 hours were allocated to civil works. This phase required meticulous planning and close coordination among the various teams to ensure safety, efficiency, and minimal impact on railway operations.
With the completion of this phase, the new railway bridge was ready to be operational, offering enhanced safety, efficiency, and sustainability. The project adhered to high technical and environmental standards, proving the effectiveness of the solutions implemented and the value of close collaboration among all parties involved.
