Compared cost evaluation among traditional versus innovative strait crossing solutions

Among the traditional solutions in use to cross waterways Cable Supported Bridges (CSB), such as suspension and cable stayed ones, nowadays represent one of the most widely realized. However this structural typology feature several problems, in particular when large spans have to be surpassed. Submerged Floating Tunnel (SFT) is instead an innovative technical solution in the field of waterway crossings, particularly suitable and advantageous in case of long waterway crossings. As a matter of fact, thanks to its modularity, the SFT structural performance is not greatly affected by the crossing length; also, its cost varies linearly with its length, differently from Cable Supported Bridges. At the stage of selection of the structural solutions to be adopted a decisive role is played by economic aspects. In particular, the building cost of each available solution has to be assessed in order to come to the final choice. Therefore simple procedures for the evaluation of the realization cost of the crossing solutions are needed; such a kind of procedures, considering only the costs related to quantity of steel, are already available for traditional Cable Supported Bridges. The scope of the present study is to provide a similar procedure for Submerged Floating Tunnels, thus allowing for quickly comparing the cost-effectiveness of the latter solutions with the one of traditional CSB solutions. Some crossing examples are also provided, highlighting the conditions where the SFT innovative solution proves to be more economically competitive than traditional ones (CSB).