PSI - Issue 84

Michela Briganti Botta et al. / Procedia Structural Integrity 84 (2026) 344–351

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3. RETROFITTING OF THE WATERPROOFING SYSTEM Based on surveys of the structures, a complete reconstruction of the waterproofing system was designed. It consists of a reinforced-concrete ballast-supporting slab along the entire length of each viaduct, compatible with the extrados of the masonry arches. The slab includes drainage grates positioned at each pier to channel rainwater into downpipes. Two major constraints must be addressed: • railway-traffic limitations requiring short, carefully phased work periods; • the need to protect the underlying roadways, ensuring safe vehicular traffic during operations. Regarding the first issue, the design includes a detailed work plan based on track closures and night-time intervals authorised by RFI. For the second issue, protective scaffolding must be erected over the roadways beneath the viaduct (Via Boveto for Barcola, and the motorway for Aurisina and Sablice). These structures will also facilitate installation of the new steel walkways on both sides of the viaducts. Waterproofing is achieved by constructing a reinforced concrete slab with a variable thickness from 35 cm to 20 cm. Once the double bitumen membrane and protective concrete screed are applied, the system will ensure adequate waterproofing.

Fig. 7. Details

The slab is built in two phases to always keep one track operational. 4. Pedestrian walkways

Steel pedestrian walkways are planned on both sides of each viaduct, to enable RFI personnel to perform inspection and maintenance operations on both tracks. The following describes the solution for the Barcola viaduct, with analogous layouts applied to the others. On the mountain side, the walkway can be installed by simply removing the existing metal parapet, providing the necessary space to widen the current pedestrian path. On the valley side, however, the walkway must be constructed above the existing masonry parapet, after removing the recently installed steel handrail (installed for maintenance purposes but insufficient in height). Several alternative solutions were evaluated, leading to the selection of the same configuration already designed and approved for the Sablice viaduct. Access to the walkway is provided directly from ballast level via a step.

Fig. 8. Barcola – Design cross-section

Since the valley-side masonry parapet is unsafe and incompatible with the new walkway, it will be demolished and rebuilt in stone in front of the walkway support columns.