Project: New structures for the MO.S.E. barriers loading-unloading operations at the Arsenale of Venice (Italy)
Location: Venice, Italy
Client: Venezia Nuova Consortium for Ministry of Public Works - Water Board - Venice
Cost of total Works: € 10,070,000
Services: Preliminary and Final Design
The northern area of Venice Arsenal is a key site for the management and maintenance activities for the MO.S.E. (flood protection) system of Venice lagoon. The area is currently used for ship maintenance and docking operations and is provided with two dry docks (“medium” and “large” dry dock) suitable for the unloading operations of the barriers.
In particular, the bank in between the two dry docks has been chosen as the main location for the unloading and loading operations: these will be “RO-RO type” operations where the barrier is unloaded from the Jack-Up vessel to modular platform trailers and vice-versa. A new landing stage, external to the bank alignment resulted as necessary in order to guarantee the best positioning of the Jack Up in respect of the trailers. At the same time a reinforcement of the existing bank has been also required in order to the heavy loads (the gross weight of the biggest barrier is about 400 tons).
In addition to the south bank of the Arsenale, the north area or the “Large” dry dock has been also designed as an alternative location for barrier unloading-loading operations: in this case the barrier placed on the trailers will be carried into the “Large” dry dock by means of pontoon and then unloaded to the north area using a steel platform.
The landing stage structure is shaped like a deck in reinforced concrete, supported by piles of concrete foundation with metal sleeve: for the construction phases, the design provides an initial realization of eight foundation piles with a diameter of 1.20 m, placed on a rectangular grid with a span of 6.00 × 6.55 m. On the top of the piles the construction of the r.c. deck plate will then follow: in particular it was considered appropriate to use the installation of prefabricated elements, with the subsequent integration of an in-situ concrete. The pier structure results detached from the existing bank, so as to highlight the distinct features in accordance with the architectonic and historical phases in the northern area of the venetian Arsenale: therefore, in correspondence of this side, the structure is equipped with an edge beam that can stand the loads transmitted by the trailer with the barrier in transit. On the other three sides, the edge beam will have an external cover with a height of 2.50 m, with upper surface at a height of +1.60 m ms and lower surface at an altitude of -0.90 m ms, in order to mask the underlying structures even in cases of low tide.
The new bank reinforcement structure has the duty to accommodate the weight of the trailer with the barrier, avoiding the new heavy loads give rise to horizontal thrust on the existing side structures: the stricture is made of a reinforced concrete slab, with a thickness of 50 cm, resting on the ground and supported by a single row of reinforced concrete piles with a diameter of 0.80 m, arranged on a longitudinal alignment next to the existing side structures.
In order to allow a stable positioning of the Jack Up vessel during the unloading and loading operation of the barrier, foundation structures are also provided in the seabed. In particular the structures are four plinths made of reinforced concrete and with an internally conical shape for the insertion of the legs of the Jack Up vessel. Each of these r.c. blocks are placed on the top of six sub-foundation piles with a diameter of 1.20 m. The top sides of the plinths will be levelled with the seabed allowing future maintenance operations of the seabed itself such as dredging or levelling.