Can be engineered Famous Italian Strait Messina's bridge?
For centuries, the idea of a bridge over the Strait of Messina has captured the imagination of civil engineers. Although the concept has been proposed numerous times, it has never been practically realized in modern times. The proposed construction has brought to mind Pliny the Elder's Natural History, which recounts the existence of a bridge built by the Romans in 251 BC, highlighting the enduring fascination with this project throughout history.
The construction of the Roman bridge was an exceptional feat of engineering due to its complexity and grandeur. It was the first and only bridge built across the strait, despite the Romans' reputation for engineering prowess. According to Pliny the Elder, the bridge was approximately 700 meters long and five meters wide. It was constructed as a "floating walkway" made up of hundreds of empty barrels tied together in a way that prevented them from touching or colliding with each other. Boats were interspersed throughout the structure, and wooden beams were placed on top to form a platform on which a layer of soil was laid. Large and sturdy wooden railings were placed on either side of the walkway to reinforce the structure and prevent elephants and carts from falling into the sea during crossings. This "modular" structure was capable of slight vertical and horizontal movement, adapting and resisting the strait's currents, gusts of wind, and tides. However, due to natural disasters that have struck the area over the centuries, there is no physical evidence of the Roman bridge today.
But how difficult was it to build a bridge across the Strait of Messina in Roman times? And how should we approach a similar project today? Firstly, the Roman bridge had to deal with different problems compared to the present day: since the Romans did not have access to the sophisticated mechanical equipment used today for engineering works, they relied solely on manual labor. Therefore, unlike today, they would not have been able to build pillars capable of spanning the entire distance between the two shores with the means at their disposal. Given these contextual premises, the construction of a bridge in that era necessarily involved implementing a "sectional connection" rather than a suspension bridge with one or more spans, as architecture understands it today. However, it was still an exceptional achievement for that time.
Speaking now about the possibility of such a project in "modern times", the geological factor undoubtedly represents the main challenge in the design and subsequent construction. The area in question is, in fact, one of the most seismically active in Italy, representing the junction of the two faults of Calabria and Sicilia. For this reason, it was considered that a traditional construction technique for such a project would be impractical, given the inherent risks in building a bridge over an essentially unstable area, even if we have technical means to cope with natural disasters. It is no coincidence that Italian regulations legally impose a series of constraints and technical-engineering requirements regarding the construction of infrastructure, especially in seismic areas, starting with the analysis of the geological characteristics of the area. The current design hypothesis has therefore ruled out a multi-span bridge from the outset, identifying on the mainland the points where the pillars would physically anchor. Even for materials, those with the best characteristics in terms of quality and durability have been considered, capable of constructing the structure adequately in terms of functional factors (i.e., in a way that absorbs as much as possible the seismic energy potentially destined for the bridge) and qualitatively in terms of temporal factors, thus requiring the treatment of the pillars and the bridge itself with insulating materials, aimed at limiting both eolian and marine erosion, (although nothing will be immersed directly in water, the bridge will be always subject to greater salinity both in the air and in the ground, due to violent sea currents). In other words, it is necessary to use the best materials that technology offers today to create a safe and stable bridge capable of resisting significant natural events. Furthermore, the bridge should also be able to cope with the issue of the annual separation between the two shores, which could cause long-term problems of "statics" (stability) for the bridge. It is estimated that the annual distance between Sicilia and Calabria increases by about 1 centimeter per year (which is not a constant factor, as for some years it may be less or greater than 2 or more centimeters due to intense tectonic movements combined with volcanic activity). All these factors contribute to the movement of the seismic faults along the Strait. To address this issue, it would therefore be necessary to construct the bridge with structural components equipped with "modular and redundant" elongation mechanisms, capable of adapting to the distance separating the two shores while ensuring maintenance without having to completely "disassemble" it or precluding its full usability during such a phase.
In summary, a structure with adequate anti-seismic measures, modularity, and a "suspension bridge" design (i.e., without pillars embedded in the middle of the Strait) is the most appropriate solution to overcome the length, avoiding the aforementioned problems. However, even once built, the problems would not end: real-time checks would become necessary, supported by advanced technologies such as physical sensors mounted on the bridge, drones, and satellites to carry out active and constant monitoring of the area of interest and the related infrastructure, in order to verify that any ground movements do not compromise the stability of the anchoring and support areas.
In light of all this, it becomes clear that this would be a project requiring more maintenance efforts than construction efforts. In a country well "known" for the unfortunate fate of similar projects precisely due to a lack of such controls and maintenance, causing more than once avoidable deaths, it represents a hurdle that is anything but easy to overcome.
Therefore, the realization of a bridge across the Strait of Messina, while not considered an unattainable dream or an unfeasible endeavor, requires efforts in a comprehensive vision. Science and technology are increasingly advanced, making it easier to conduct studies and seek innovative technical solutions to address difficult but not impossible problems. However, it is the action of humans that ultimately decides the outcome, just as the Romans did by adopting the best engineering solutions available at the time.
In any case, let us reflect on the technical creativity of the human mind, which has always driven it in every era to achieve grandiose works. Anyway, also science and technology must face time aging, teaching us that building itself it's not enough, we must also preserve.