The solar-powered bridge is the first to use robots for cleaning and inspection.
Genoa’s new bridge may not have the massive pillars and cables of the Morandi Bridge it replaced, but what it may lack in flair, it more than makes up for with its elegant design and technology most grande.
The San Giorgio Bridge, completed in 2020, two years after the deadly collapse of the Morandi Bridge, is both a testament to the value of age-old construction material (concrete) and a showcase for the most innovative bridge technology.
The new bridge is 3,501 feet long and consists of 19 spans supports by helical reinforced concrete columns. Barriers made of glass provide views of the surrounding valley and mountains while casting less shadow on the citizens below. Solar panels provide power to the bridge lights. The length of the bridge is studded with sensors to measure movement, such as joint expansion, forming what amounts to a futuristic central nervous system.
World-famous architect Renzo Piano, a native of Genoa, designed the San Giorgio Bridge. His design evokes the shipping trade in which his city is steeped.
The Genoese once vied for the Mediterranean with the Venetians during the time of Marco Polo. Cristoforo Columbo (we know him as Christopher Columbus) hailed from Genoa, though he sailed sponsored by Spain’s flag for his most famous voyages.
“From an architectural point of view, the form described by the deck, which recalls the hull of a ship, is of great importance,” said Piano. “The gradual reduction of the section towards the ends of the bridge attenuates the visual impact of the new infrastructure. In addition, the use of a light color for the coating of the steel elements makes the bridge bright, harmonizing its presence in the landscape.”
Meet the Robots
The bridge brings a stunning level of innovation and makes the most of engineering simulation and technology.
Keeping a close eye on—and under—the San Giorgio Bridge will be a pair of two-ton robots that survey the entire underside of the deck every eight hours, sending 25,000 pictures back to engineers in real time.
The robotic system features cameras and sensors that feed predictive algorithms to help predict maintenance needs and monitor the safety of the bridge. Designed by Istituto Italiano di Tecnologia (IIT) and the Camozzi Group, the automated system consists of two robots that survey the bridge (Robot Inspection) and two robots that clean the glass barriers and solar panels (Robot Wash) on the structure’s parapet. This is the first system of its kind to be installed on a major structure in the world.
For the robots to be useful and reliable on a bridge so close to the Mediterranean Sea, they had to be lightweight and durable while facing constant exposure to the elements. IIT’s experience working in industrial robotics and Camozzi’s expertise in automation and mechatronic mechanisms were key to winning the design. The robots combine elements of industrial automation, robotics, machine learning and aerospace engineering.
Each nearly 5,000-pound Robot Inspection device moves along the bridge on tracks mounted on either side of the parapet. Each robot has a retractable arm that can reach from the edge of the underside of the deck to the center. High-resolution cameras and sensors installed on the robotic arm transmit data to the engineering staff and 3D models and allow monitoring of paint condition, corrosion and the condition of welds subject to fatigue loads. Should a storm start battering the bridge, the robots retreat to their charging stations.
To help limit the amount of time that human maintenance workers need to spend on the bridge, the Robot Wash system travels along the edge of the structure’s barrier to evaluate the transparency of the glass. To save water, the robots will clean only when dust and debris reach a certain level on the barrier or solar panels. During an extended drought or water shortage, the robots switch from “washing” mode to a blower. All the water used by the robots is collected from rain and condensation collected on the bridge, providing a sustainable, efficient system.
From a Troubled Past
Tragedy struck Genoa in August 2018 when the soaring Morandi Bridge carrying the A10 through the city collapsed, killing 43 people. The exact cause is still under investigation by leading structural engineers who have spent countless hours in research and analysis. Theories include heavy traffic on an aging structure, corrosion from salty sea air, industrial pollution or rising river waters and flooding brought on by recent heavy rains. Some eyewitnesses claim that the bridge was struck by lightning before its collapse.
The Morandi disaster was a stunning blow to a nation proud of its engineering—from the ancient Romans to present day Ferrari. It left the Genoa reeling—but also gave the city an opportunity to rise from the rubble and rebuild.
The Morandi Bridge was thought to have added to Italy’s engineering legacy, soaring nearly 150 feet over the Polcevera Valley below with its three-quarter-mile length of prestressed concrete pylons and cables. The bridge, designed by Riccardo Morandi, pushed the limits of cable-stayed construction, with only four cables per tower and a deck made entirely of reinforced concrete.
Claims made about the bridge at the time of its construction were bold, including the belief that covering the cables in prestressed concrete would eliminate the need for future maintenance by virtue of the coating’s ability to protect the steel from corrosion.
After World War II, Italy emerged as a leader in concrete construction. It had little choice. Postwar sanctions following the collapse of Italy’s fascist government made for a scarcity of steel. Materials for concrete, however, were in great supply.
But pushing the envelope with a new style of construction raises risk and adds uncertainty. For the Morandi Bridge, the uncertainty revolved around the concrete’s ability to protect the steel cables from chemical breakdown in the presence of higher levels of pollution and increased loads from traffic. Engineers of that time did not grasp the importance of durability, consistent maintenance and resilience as they do today. The Morandi Bridge soon began showing signs of trouble.
“When I visited the bridge in the early 1990s for a documentary on Morandi’s work, I was surprised to see fissures and corrosion just 20 years after its completion,” said Giuseppe Imbesi, an architect who worked with Morandi on a bridge proposal for the Strait of Messina.
Italian infrastructure conglomerate Autostrade per l’Italia began retrofit efforts on the bridge in 2018, but it was too little, too late. Decades of inaction had pushed the Morandi Bridge to its limit. The main cables were already highly corroded and their protective concrete coating was largely cracked and not functioning as intended.
The Future of Bridges
The San Giorgio Bridge is an outstanding work of design and construction and will serve the city of Genoa. But it doesn’t stop there. It is an example to the rest of the world on the use of technology for the construction and maintenance of bridges.
As aging infrastructure across the world is rebuilt and replaced, we cannot rely on traditional methods of inspection and maintenance. New technologies must be developed and implemented to bring bridges to life and allow them to provide more immediate feedback to the engineers tasked with maintaining them and understanding their behavior. Sporadic inspections, regardless of how thorough they may be, cannot provide the feedback and data gained from sensors and daily robotic sweeps of the bridge.
Use of the latest technology is most important for larger, more sophisticated bridges. Embracing technology will ultimately save millions of dollars in maintenance costs by allowing preventative maintenance to be more fluid, enabling bridge inspectors to focus their time on the vital parts of the bridge to save lives by preventing a tragic collapse.
