Genoa’s new bridge must cannot collapse

Almost two years after the disaster with the Morandi viaduct in Genoa, its successor was inaugurated beginning August. Steel, concrete and smart electronics will ensure that the bridge will last one hundred years.

Let the numbers speak for themselves. The new Genoese bridge is 1067 meters long and counts 19 spans, which are supported by 18 pylons measuring 40 meters in length.

While Renzo Piano cannot be expressed in a number, it was this architect – one of the most renowned in the world – who designed the bridge. This doubles the beauty of it. Renzo Piano was not only born in Genoa, but he also dispels the cliché ( commonly known in Italy) that the inhabitants of Genoa are stingy: the 82-year-old top architect completed his project for free.

Time factor

But what stirs the imagination most is the time factor. The bridge has been built in breakneck tempo. Even the corona crisis did not throw a spanner in the works. The first pile foundations went down in June 2019, and today, the Italian president is officially inaugurating the bridge.

“One of the greatest challenges for the work was that we did not do one, but two things at the same time. The old Morandi Bridge was demolished and the new bridge was built in parallel,” says project manager Andrea Tomarchio of RINA, a company specialized in certification and industrial services. He and his team supervised the entire project. The client, the government, had one clear stipulation. The bridge had to be constructed within two years. That was why it was not possible to wait until the Morandi Bridge was dismantled. Remnants of the old bridge finally collapsed once all parts of the remaining bridge were blown up in a controlled manner. This happened in an urban environment without the population being afflicted by dust and grit. According to Tomarchio, this was unprecedented in the world.

Pylons

The viaduct, which stretches for more than a kilometer, crosses a river, a railway line, residential buildings, and business premises, among other things. There is also a gas pipeline underneath. The bridge consists of 18 elliptical shaped pylons with 19 spans running above them. Architect Piano opted for an ellipse because this shape reduces the amount of light being blocked underneath the bridge. The slender, tapering pylons are slightly reminiscent of skyscrapers. The pylons are not all equally spaced apart from each other. The middle four are further apart because they carry three spans of 100 meters in length each. The other spans are about 50 meters across.

The concrete pylons will not ‘break down’ any time soon. The foundation piles are at least 50 meters deep in the ground. “The bored piles penetrate so deep into the ground because they grab the rocky ground at that height. They are anchored about four meters into the rock,” says Tomarchio. The bored piles are made of 1.5 meters thick reinforced concrete. There are eight such piles under the pylons at the beginning and end of the bridge, the ones in the middle that absorb the most pressure have double the number of bored piles beneath them. The pylons are over 40 meters high.

Spans

The steel spans were built at two yards of the Italian shipbuilder Fincantieri, which also undertakes infrastructure projects. The gigantic prefabricated components were assembled and hoisted up at the construction site. Last October the first span was raised, six months later the last part of the bridge was hoisted up. The largest span weighs 1800 to 1900 metric tons, Tomarchio says. A giant jack, a so-called sand jack, was used to hoist these spans. These are capable of raising such enormous components at a speed of 5 metres per hour “as a kind of lift”. Motorists will not notice that the bridge has nineteen spans. The road surface is made up of one piece. “We’ve opted for the comfort of the motorist and have therefore built a so-called integral bridge.” The joints between the spans are eliminated on this type of bridge.

Smart

In order to avoid another tragedy, considerable investments have been made in maintenance and inspection measures. Solar panels attached to the bridge produce the energy needed to operate the bridge. Two robots are in continuous operation to clean the solar panels. They also scan the bridge construction regularly to detect any anomalies and critical points. Technology from the maritime sector has been used for the bridge for the first time on land. That is the advantage of having Fincantieri, shipbuilder and infrastructure developer, on board. The sensors installed use an algorithm that improves the performance of the computer the more data it is exposed to. This makes it one of the first ‘smart’ viaducts in Europe.

The bridge is already the pride of Italy. There is no doubt that the construction went without a hitch. Who would have ever believed that? This is pretty much what you would think when it comes to infrastructural projects in this country. For example, the motorway between Salerno and Reggio Calabria (southern Italy) was definitively completed in 2016, 55 years after the start of the endeavor.

Eminently Italian

The project to demolish the old bridge and the new buildings, in particular, was entrusted to two large Italian construction companies and numerous other Italian subcontractors by a special government commission. “At least 90% of the bridge is Italian,” says Tomarchio. “If I’m not mistaken, only a certain type of girder was made in German.” Most of the material also comes from Italy. The concrete is actually from Liguria itself, the region of which Genoa is the capital.

The bridge is also eminently Italian, because the design, no matter how simple, is incredibly elegant. The architect Piano states that the bridge has the shape of a ship. Ships are a part of Genoa, the largest port in Italy. The bridge is therefore quintessentially Genoese. This is apparent from the name of the new bridge: Genova San Giorgio (Genoa Saint George). The St. George’s Cross is in the flag of Genoa. George is also the saint who defeated the dragon. This reference is of naturally not coincidental.

The bridge is a keeper. “The project expects that the bridge will last one hundred years. “I can safely say that it will be there for many more years after that,” says Tomarchio with a smile. The last thing they want in Italy is to experience the tragedy of the previous bridge.

14 August 2018

It is shortly before noon when a severe thunderstorm hits Genoa. Then a lightning bolt is seen above the viaduct over the Polcevera, followed by an explosion. Immediately after that, part of the suspension bridge, which is over a kilometer long, collapses. Dozens of cars and a few trucks fall some fifty meters below the bridge. Under the viaduct, business premises and homes are covered in rubble. The devastation is enormous and the toll of years of overdue maintenance is heavy. The death toll stands at 43 people.

Published originally in Innovation Origin.