PSI - Issue 84

M.P. Petrangeli et al. / Procedia Structural Integrity 84 (2026) 135–142

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The increasing of foundation capacity, required for carrying the increased traffic loads due to the platform widening and the updating of the design traffic loads as per current Italian code, has been obtained executing, all around the perimeter of each pier-foundation, jet grouting columns with 1.7 m up to 2 m in diameter; the loose material filling the pier pipe has been consolidated by means of jet grouting columns, also. The design and the site supervision of the jet grouting works have been executed by Eng. Luigi Albert - Soil Engineering SRL. 8. The restoration of the original deck As premised, the parabolic steel truss beams are an important part of the “Industrial archaeology” that characterizes the “Ostiense” neighborhood and are under the protection of the Ministry of Culture, by law. As a first step of the restoration works, after demolishing the concrete slab and consequently reducing to 85 tons the weight to be lifted, the whole truss beams have been lifted and removed using 600 tons capacity cranes operating from the river embankments. Then, the truss beams have been placed on the river banks for the restoration; since the spacing of the two main beams has to be enlarged to fit the new widened road platform all the cross members have been removed to facilitate the restoration and subsequently reinstalled in place after the variation of nodal geometry required for enlarging the deck. After the completion of the restoration the original beams have been reinstalled onto the new structural deck that carry their weight.

Fig. 11 (b). Relaunching of the original truss beams using a 400 tons crane

Fig. 11 (a). Removal of the original truss beams

Specifically, the original truss beams have been relocated right outside the new structural truss beams, bearing over specifically shaped lateral cantilevers designed for carrying the truss weight in addition to the load of lateral pedestrian/bicycle pathway. 9. Execution of the new structural deck While the restoration of the original deck was being carried out (taking all the due time as happens when artistic or historical artefacts are involved), the new structural deck has been executed as quickly as possible in order to reopen the bridge and ease the traffic congestion, heavily increased during the works, being the bridge under discussion one of the few that cross the Tiber river in that area of the city. A macro segment of the deck has been assembled for a length of 50 m on the right bank, where there was the required space, fastening with bolts the 11.5 m long prefabricated segments of the main truss beams and welding at site the orthotropic deck plate segments; the deck has been placed 1.5 meter above the road level in order to improve the accessibility and ease the execution of the bolted and welded joints. Subsequently, the deck has been incrementally launched, with the help of a short launching nose and temporary counterweights strictly required during the initial stages of the launching phases, only, in order to balancing the cantilever before the first landing of the launching nose. After the completion of the incremental launching stage, for a total length of 107 m, the continuous beam, bearing temporarily almost 4 meters above the pier top level, has been lowered working simultaneously over 2x4 jack points. After having completed all the structural works and opened the bridge to traffic, the bridge appeared as shown in the next picture: