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was a star engineer in Italy at the time. He designed dozens of bridges, and they were all very aesthetically- pleasing. “He was the best designer-engineer of all of Italy,” says Lori. His designs were characteristically nuevo, daring, aesthetically pleasing, and often achieved with the use of wire rope. Moldani’s bridge was revolutionary at the time but it was designed with numerous “single point failures” at numerous connection points. In August 2018, the southeast cable stay on plyon nine fully snapped apart at the top connection point, causing a portion of the roadway to waive, sag, and then fully collapse, taking down more of the bridge with it. Unfortunately, Moldani’s bridge was near to or completely finished by the time civil engineers realized bridges should not have “single point failures,” as a result of the Silver Bridge collapse of 1967 in West Virginia. In the case with the Moldani bridge, the 52 steel cable wire ropes were post-tensioned, then encased in steel sleeves, and then pumped full of concrete grout. Careful research shows that when the concrete grout was originally pumped into the steel sleeves, there were air pockets that left parts of the steel wire rope exposed to future corrosion.


A NEW BRIDGE LIKE A SHIP MOORED IN THE VALLEY


As decades of bridge-making continue, worldwide civil engineers become more and more technologically savvy and better at bridge making calculations. Every single bolt and connection is scrutinized and lessons are learned from these rare but tragic collapses. In the case of the Moldani bridge, the people of Genoa were no longer trusting of the wire rope bridge aesthetic. It was not a design that they could support any longer emotionally. Yet, cutting edge technologies have been developed to both search out signs of corrosion with impeccable precision and to better prevent corrosion from occurring with wire rope construction now and in the future. Engineers are hoping that lessons from the Polcevera collapse will help to preserve many other bridges worldwide. In Renzo Piano’s new design, “the piers [and bridge


deck] are elliptical in shape, allowing the light to slide off the surface and soften the visual impact that the bridge will have in its urban setting,” says the general contractor Salini Impregilo, who formed the PerGenova joint- venture with Fincantieri, the premier Italian shipbuilding construction company. Approximately 600 workers have been working non-stop on-site since June 24, 2019, even when Italy was hit the hardest during the coronavirus pandemic. Te piers were constructed on-site, but the spans were precast off site & hoisted into place once the piers were completed. A strand jack was used to pull the deck spans up into place, each raised at only five meters per hour. A single steel girder stretches 1,067 meters long as a main support for the deck. Te 19 reinforced


Lifting operations on Span #8


Photo courtesy of Pergenova


concrete piers are buried 50 meters underground and are 80 meters tall in total. While the previous Moldani bridge had only eight piers and nine spans, the Piano bridge has 20 spans. Also, as a precaution, the new bridge is expected to withstand an earthquake. Renzo Piano’s design is inspired by the imagery of a keel of a ship, which is partially why the shipbuilding company Fincantierai is involved. “Te new bridge will have to be simple and parsimonious, but not ordinary. It will look like a ship moored in the valley; a light and bright, steel bridge. By day, it will reflect the sunlight and absorb solar energy, returning it at night. It will be a distinguished bridge, reflecting the character of the people of Genoa,” says Renzo Piano. Te steel for the bridge is coming from the same steel supplier that Italy used for their Navy. All of the stone used for the project is coming from the exact same quarry so that the overall color and look is harmonious. Te view from underneath is probably the most gorgeous view. Part of the project includes a new civic park to be developed below the bridge as well. Te bridge will have one lamp lit for each of the individuals who lost their lives in the collapse. On the cutting edge of technology, the Renzo bridge will be eco-friendly with solar panels on the south side that will cause the bridge to be energy self- sufficient. Furthermore, a fleet of robots will travel along the surface of the bridge continuously to monitor signs of failure. Te robots will also help to monitor traffic flow patterns and provide accurate data that can be used to further analyze future failures. A special dehumidification system to avoid the formation of salt condensation and corrosion is also installed within the bridge system. “Te story of this bridge shows that the competence is there, the technology is there, even the passion is there,” Piano said. “Making buildings is a gesture of optimism. I’m not surprised that somebody takes it as a sign of hope.” Te new Polcevera (Renzo Piano) bridge is expected to open fully for public use in July 2020. y


WIRE ROPE EXCHANGE MAY–JUNE 2020 31


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