THE ME-RC BRIDGE (Messina-Reggio Calabria) Giovanni Saccà1 The Messina – Reggio Calabria bridge as integration solution for two metropolitan cities ABSTRACT Numerous hypotheses and projects have been made to overcome the Strait of Messina, most of which are located in the narrowest area or in correspondence of the "Sella dello Stretto" where the minimum distance between the coast of the Italian peninsula and Sicily is reached (Scilla and Cariddi). As is well known, unfortunately, the chosen solution of the 3,300 m single span bridge has never been realized despite the fact that a special international tender has been carried out since the contract was declared lapsed pursuant to Law 1158/71 and the Company Messina SpA has been placed in liquidation. In the Document on Economics and Finance 2017 (DEF 2017) annexed "Infrastructures" of Italian Government, as part of the priority railway interventions, it was envisaged that a "Feasibility Study" should be prepared with a view to enhancing the possible options for both stable and non-permanent crossing the Strait of Messina along the "Napoli-Palermo" corridor. This intervention was also included in the attached DEF 2018 "Connecting Italy" for the Southern Region (or “Mezzogiorno”), which states, inter alia, that for the crossing of the Strait a feasibility planning phase is underway: "The options to be considered for the verification of feasibility of the connection, stable or not stable, through the Strait of Messina, will refer alternately to the road, railway or maritime mode". This article aims to contribute to the search for a solution to permanently cross the Strait of Messina, while at the same time solving the problem of integration between the two metropolitan cities of the strait in a single large city. 1 ing. Giovanni Saccà, dean of the CIFI Section of Verona - http://www.cifi.it/Ppresidi.asp 1 Introduction The idea of creating the ME-RC bridge originated from the examination of the “Sulafjorden road crossing project” prepared in 2015 by RAMBOLL & SWECO for the Norwegian Public Roads Administration (Statensvegvesen) as part of the project to adapt the E39 highway. Among the 43 alternatives examined to overcome this strait, we considered the solution of creating a 2000m two-span suspension bridge with a fixed foundation along corridor 2 using GBS (Gravity Basic Structure) technology (Fig. 1 and 2). Fig. 1 – Alternatives considered to overcome the Sulafjorden 2 2 https://www.vegvesen.no/sok?query=Sulafjorden 2 Fig. 2 – Corridors taken into consideration for the crossing of the Sulafjorden The corridor 2 provides for the crossing of a stretch of sea 4100m wide and 450m deep. In order to realize the central tower of the bridge, we considered the idea of constructing a Condeep (Concrete Deep-Water Structure) consisting of 23 base cells, 4 of which designed to escape from the water and support the steel tower, and 2 designed to increase the horizontal stiffness of the structure (Fig.3). The base cells of the Condeep have a height of 56 m (Fig. 4). The four main columns of the Condeep extend from the basic structure up to 30 m above the surface of the water to support the tower. Between the four main columns and the base of the steel tower, in the form of a double capital letter A, many transition elements have been designed (Fig.5). The steel tower above the four main trees of the Sulafjorden bridge is about 245m high (Fig. 6, 7 and Tab.1). 3 Fig. 3 - Bridge pylon designed with GBS technology 3 3 Youtube “Video animazione Statens vegvesen - E39 Sulafjorden K2” https://www.youtube.com/watch?v=7s2l7Uq_oZ4 4 Fig. 4 – Schema realizzativo della struttura di base del Condeep Fig. 5 - Elements of transition between the four columns of the GBS structure and the steel tower out of water 5 Fig. 6 – Suspension bridge with two spans for crossing the Sulafjorden along corridor 2 Total length of the suspension bridge m 4000 Span length of the suspension bridge m 2000 Navigable height m 75 GBS column size m Di = 32.0 at the bottom of C = 18.4 at the top Total height GBS m m 480 (senza gonna) GBS base area m2 20 500 epth of the GBS skirt m 20 GBS concrete volume m3 338500 (407,000 water depths 450 m) Distance between the four GBS columns at the top m 64m x 110m Height of the steel tower placed above to the four columns of the GBS structure m 245 Tab. 1 – Project data of the two-span suspension bridge with GBS foundations on the Sulafjorden 6 Fig. 7 – Measurements of the steel tower of the 2000m two-span road bridge designed for crossing the Sulafjorden along corridor 2 The GBS structures can be designed to resist not only at the vertical load of the bays, but also at the horizontal thrusts due to wind, thrusts due to sea waves, possible earthquakes, naval impacts and impacts against icebergs. Among the numerous calculations to be carried out, it is important that the proper period of the GBS structure does not coincide with the wave period to avoid that the structure resonates. In the case of the Sognefjord (Fig.8) the measured period of the waves is between 12 and 14 seconds. For this GBS construction the self-oscillation period was calculated in 6.33 sec. 7 Fig. 8 – Design of the two-span bridge for crossing the Sulafjorden along corridor 2 Condeep structures have been built since 1973 for the increasingly widespread offshore fixed platforms for the extraction of large deposits of crude oil and natural gas (Fig.9). Normally, the vertical elements support a platform, with machinery and spaces for the crew and given their distance from the coast must be designed with safety criteria such as to constitute a safe place even in areas with seismic danger and very high waves. These structures are part of the Gravity-based Structures GBS category, i.e. support structures that support and resist external stress by exploiting gravity. A Condeep structure generally consists of a reinforced concrete base for the storage of oil or gas from which then rise, for about 30 m above the mean sea level, three or four "pylons" (towers) of reinforced concrete containing ballast and machinery like drilling machines. 8 Fig. 9 - Concrete platforms installed by Norway in the Atlantic Ocean Source: (www.olavolsen.no) To date, the largest Condeep structures built are the 610 m high Petronius Platform and the 472m high Troll for whose stability 35 m deep foundations have been built at the bottom of the sea. Currently, these structures have been built up to a depth of 300 m and with the progress of construction techniques such constructions are considered possible up to a depth of 500m. In the case of the bridge over the Sulafjord, the depth of the sea at the point chosen for the construction of the Condeep pylon is 450m, so that the overall height of the structure (Condeep plus steel tower) is about 720 m (Fig.8). The Messina Strait bridge Numerous hypotheses and projects have been made to overcome the Strait of Messina, most of which are located in the narrowest area or in correspondence of the "Sella dello Stretto" where the minimum distance between the coast of the Italian peninsula and Sicily is reached. Taking into consideration only the hypotheses analyzed for the Strait of Messina since the eighties of the last century, almost all the solutions were related to bridges with one or more spans (Fig. 10). 9 Fig. 10 – Location of the bridges for the permanent crossing of the Strait hypothesized by the Strait of Messina Company S.p.A. (SdM). In Figure 9, the solutions with several spans discarded from the first phase of study are indicated in black. The points placed in the middle of the sea indicate the position of the pylons that had been identified in places where the sea was deep at most up to 145m. Lastly, the two solutions indicated with the color red remained. Among these it was chosen that without a pillar placed in the middle of the sea to avoid the danger of collisions of ships, because in this area the sea currents in some moments can be particularly swirling and fast. As is known, the bridge chosen was that of a single span of about 3,300 m (red line highlighted with the words "FINAL ALIGNEMENT" of Fig.10). In the same area the hypothesis of creating a bored tunnel had been considered (Fig. 11). 10 Fig. 11 – Location of the road and railway bored tunnels taken into consideration by the SdM. This solution was judged achievable at the "Sella dello Stretto" at a depth of more than 150-170 meters below sea level. But it was rejected for a whole series of reasons listed in the book "The Messina Strait Bridge" edition of CRC PRESS and the Strait of Messina "2010: “In summary, while bored tunnels in the Strait are certainly feasible, their principal drawbacks are: - Difficult boring conditions at the depths required in the specific geotechnical conditions; - Uncertainties in costs and technical Solutions for the advancement through the fault areas; - Extremely high construction costs, evaluated to be several times higher than for any bridge scheme; - All the negative functional aspects of very long tunnels with free road traffic connected with exhaust gas handling; - The risks connected with accidents-terrorism-sabotage within the enclosed tunnel body, for a piece of infrastructure that would possibly become an internationally sensitive target. Hence such schemes were not selected for further consideration.