The 1960s saw significant growth for many industrialized countries. As automobiles started to become the norm, highway systems were needed to accommodate the increased traffic. Instead of having this traffic meander up mountains, Genoa, Italy, was designated as the location for a new, modern bridge that would bypass the city and cross the Polcevera River. Designed by Riccardo Morandi, the Morandi Bridge became a modern wonder that was plagued with issues that would eventually lead to a devastating collapse and the need for a quick rebuild.
A Problematic Infrastructure
As part of the A10 motorway, the Morandi Bridge was a necessary structure for the new highway network connecting districts across the Polcevera Valley and serving as an arterial roadway of European Route E80 for travel between Italy and France. A unique challenge for its design was that the bridge had to be constructed over an existing city.
Construction of the bridge began in 1963. Morandi based it on his design for the General Rafael Urdaneta Bridge in Venezuela. Completed in 1962, that bridge still stands but suffered collapsed parts from a tanker collision in 1964 and has shown signs of potential fractures. Morandi was known for his cable-stayed bridges, which were just beginning to gain popularity at the time, and his use of reinforced and prestressed concrete structures. In post-World War II Italy, steel was in short supply and very costly. Engineers had to look for more local sources, such as the abundant sediments needed for concrete.
The bridge design included one pair of stays for each roadway section using concrete reinforced with steel tendons. Unlike the dozens of cables used today, the Morandi Bridge had four cables per tower that were covered in prestressed concreted. The bridge also featured trestles that formed a double V. One supported the tie rods, while the other supported the roadway beam.
Completed in 1967, the finished structure was a 3,878-foot bridge that was 148 feet at road level, spanning 690 feet and featuring 300-foot towers. The impressive structure was considered as strong as but lighter than other bridges since it used less steel. Its sleek look and innovative design seemed to be a beacon of Italian engineering. Within a few years after it opened, Morandi acknowledged that the bridge would need ongoing and frequent maintenance. Unfortunately, the bridge’s concrete encasements made it difficult to inspect.
The bridge quickly started showing signs of potential problems, but they were not considered a threat to its structural integrity. Signs of corrosion, fissures and a deformation in the concrete under load soon appeared, which required repairs to the bridge’s deck to enhance planarity. In 1979, Morandi created a report that offered preventive measures to reduce the effects of the salty sea air and factory pollution on the bridge.
In 1992, the 25-year-old bridge was being monitored by Società Autostrade, which at the time was a state-owned company belonging to the IRI Group that would eventually be at the center of suspicion after the bridge collapsed. It found a construction defect on Tower 11, which had been the first to be built and was on the Genoa side. A rehab project was set in motion to address the issue. Instead of replacing corroded cables, new ones were added except to two sets. Throughout the next two decades, problems continued that required maintenance and foundation work.
The Collapse, Speculations and Multiple Causes
At 11:36 a.m. on Aug. 14, 2018, the unthinkable happened. As heavy storms blew through Genoa, one of the 50-year-old bridge’s cable stays broke, taking a supporting tower, a 690-foot bridge section and vehicles along with it onto the city streets below. The devastation resulted in the deaths of 43 people.
Rumors, speculations and questions instantly began to swirl around what the true cause of the collapse was. The initial thoughts were that it was caused by a landslide, lightning or structural weakness. Videos of the collapse showed that the stays and road section dropped at nearly the same moment, immediately followed by the pillar. With the bridge’s history of corrosion and other potential maintenance neglect, all eyes quickly landed on Autostrade, which was a holding company under the Atlantia parent group owned by the Benetton family that privately operates motorways and airports.
Along with the political component, the bridge’s age, potential neglect and decades of repairs, a number of other factors likely played a role in the collapse. From the beginning, the bridge was built with concrete, which is now known to last only 50 to 100 years. Rumors speculated that the concrete itself may have not been the highest quality in an era where corruption was commonplace. Salty air, extreme storms and high flowing river water likely impacted the bridge’s integrity.
Another contributing factor was the traffic itself. When the bridge was built, the level of traffic on the roads was significantly less, so the bridge was designed to accommodate a certain traffic load. The following decades led to overloading the bridge. In addition to the weight, the added wear and tear from more than 10 times the expected traffic impacted its integrity.
What was the true cause? Experts aren’t able to pinpoint an exact cause, which means the above speculations were potential contributing factors to the disaster. Although it took time and community and political efforts, it was agreed that the neglect by a privately owned company in charge of an aging infrastructure played a major role. A ruling in July 2020 resulted in the transfer of control of Autostrade to state lender Cassa Depositi e Prestiti (CDP). While the Benetton family will receive money for its stake in the company, Autostrade is required to pay $3.9 billion in compensation. There is also a pending culpable homicide lawsuit against the company and several transport ministry officials.
Rebuilding with Technology
Although the impact and devastation of the collapse will forever haunt the citizens of Genoa, the bridge was a vital part of its infrastructure. Shortly after the bridge collapsed, it was announced that the old bridge would be torn down and a new one would be built. Just 18 months after the demolition of the original bridge, a new bridge was inaugurated.
Four months after the bridge’s collapse, Architect Renzo Piano, a Genoa native, was selected to design the new bridge. Italferr, an engineering company, was chosen to see that design come to fruition. The 3,500-foot urban bridge has a steel deck with 19 131-foot spans, 18 reinforced concreted piers and two adjacent piers, as well as metal fins on the sides with two rows of solar panels.
While the aesthetics of the design pays tribute to Genoa’s maritime history—the deck is reminiscent of a ship hull—the process throughout the design and construction was immersed in technology, innovation and experience. Each step involved the use of Bentley BIM to provide a digital twin for every component, including the terrain, route, road, steel and concrete structures, as well as the mechanical and electrical systems. This technology helped reduce costs, enhance collaboration, and provide more accurate calculations.
The process started with taking a laser scanner on a flight over the area. These scans provided the needed details that could be digitally reconstructed into a 3D surface of the bedrock, enabling precise depth measurements needed for the foundation piles. From there, templates were made for the placement of components both small and large. Each required a dataset with information on physical elements and the construction schedule, as well as dimensions, volume and other vital factors.
From the photovoltaic system to dehumidification system and metal structures, the digital twins helped ensure that compatibility between systems, precise positioning of components and maintenance for auxiliary systems would be easier. It even allowed for the simulation of airflow inside the deck, which helped determine how many units were needed.
As other vital bridges and structures begin to show their age or weakness, hopefully the Morandi Bridge will continue to serve as a reminder that not everything was built to last. However, with technology and innovation integral to new structures, perhaps Piano’s words that this bridge is expected to last 1,000 years will ring true.