By Lorella Angelini, Angelini Consulting Services, LLC
This post is dedicated to the innovative, robotic solutions for cleaning and inspection that were implemented in the new construction of the San Giorgio Bridge, in Genoa, Italy (see LINKS)
This major urban bridge (Pics. #1 and #2) replaced the Morandi Bridge over the Polcevera river that dramatically collapsed on August 14, 2018 taking the lives of 43 people. The new San Giorgio bridge, which was inaugurated on August 3, 2020 with the Italian President, Sergio Mattarella, in attendance, was built in 13 months through a collective effort that encompassed the work of 330 companies and 1000+ people.
The architectural design of the San Gorgio Bridge is the work of the Piano Building Workshop (RPBW) design firm (see LINKS) based in Genoa, which is led by the renowned designer, Renzo Piano. Genoa is a major harbor on the Mediterranean Sea that gave birth to so many seamen, not to mention the likes of Christopher Columbus. Setting up an ideal connection between the bridge and the essential maritime character of the city of Genoa, Piano designed the box steel girder supporting the deck with a unique elliptical shape that resembles the keel of a ship. The girder, whose components were built at different Italian shipyards, continuously spans for 1067 metres (3,501 ft) over 18 reinforced concrete piers. The continuity of the girder is allowed by an advanced bearing system that isolates the continuous girder from the piers and also protects the bridge against potential seismic activity.
Between the many outstanding qualities of Renzo Piano, there is his willingness to embrace the most advanced construction technologies. He has been known to speak of maintenance as an act of “care” toward bridges and buildings that ultimately make them last long. In the case of the San Giorgio Bridge, he combined his focus on advanced technologies and his emphasis on maintenance by envisioning the use of mobile robots permanently installed on the bridge deck. Renzo Piano discussed the idea with Roberto Cingolani, who was the Scientific Director of Istituto Italiano di Tecnologia (Italian Institute of Technology – IIT) (see LINKS), also based in Genoa. Then the task of bringing Piano’s vision to fruition was taken by the Industrial Robotic Unit (IRU) of IIT, which is accustomed to working with industry.
I reached out to the Head of the IRU, Ferdinando Cannella. Not only did he create the robot for cleaning that was requested by Piano, so-called RoboWash, but he also ideated a second robot for performing inspections, named RobotInspection. Ferdinando (see LINKS) graduated in mechanical engineering from Marche Polytechnic University, has a PhD from Padua University in Mechanical Measurements and a second PhD in Mechanical Engineering from Marche Polytechnic University with the entire robotics program developed at King’s College in London, UK, under supervision of Prof. Jian Dai.
I had an extensive conversation with Ferdinando about the RoboWash and the RobotInspection. During the conversation I also learnt that we come from the same Marche region of Italy and, quite unexpectedly, graduated from the same Marche Polytechnic University.
Could you briefly describe the two robots, the RobotInspection and the RoboWash, that are installed on the San Giorgio bridge?
Both the RobotInspection and the RoboWash (Pic. #3) move longitudinally along the rails placed at the two sides of the deck making a total of four robots. The two robots look distinctively different from one another.
The RoboWash is a compact robot (Pics #4 and 5) designed for cleaning fully autonomously three glass surfaces: the wind barriers (on the two sides) and the solar panels (see Pic. #6). It weights approximately 2000 kg (4409 lbs.), which are distributed on 56 wheels. It is 3,5 meters (11 ft) tall, 8 meters (26 ft) long and consists of two parts, one for the actual cleaning and the other for energy recharging.
The RobotInspection is essentially a carbon fiber beam with a fixed section and a retractable one. When the retractable beam is fully elongated, the RobotInspection reaches 17 meters (56 ft) in length (Pic. #7). The robot weighs 2200 kg (4850 lbs.); it is 7-meters (23 ft) wide and is anchored to the rails with 56 wheels. Another 26 wheels are in place for moving the retractable beam. The robot moves at a rate of 100-150 mm/s (20-30 fpm) over the rails. This is the same speed as the RoboWash.
The RobotInspection was not envisaged by the designer of the bridge. It was actually my idea. When I was told that the designer wanted to install a robot for washing the sound-barriers and the solar panels, I raised a question: “Why don’t we take advantage of the rails for RoboWash to add another moving robot that would inspect the bridge deck?” After some initial hesitance and a lot of work, that idea became reality.
As reported in the bridge’s inspection manual, the RobotInspection is responsible for fully autonomously monitoring the exterior of the steel girder. This is the robot’s primacy compared to current robots in use. As an additional feature, this robot is also suitable for a semi-autonomous inspection of the bearings.
How does the RoboWash work?
This RoboWash removes dust and other contaminants from the glass surfaces of the two sides of the wind barrier and the photovoltaic panels that supply power to the RoboWash itself and to the bridge’s utility components, such as the dehumidifiers that are installed inside the steel box girder, in the proximity of the inspection catwalk.
The RoboWash is a self-sustained system that uses rain water and condensation water collected on the glass. The robot does not use any detergent, thus preventing the risk of chemical pollution of the Polcevera river due to runoff. If rain is scarce or condensation is low, the RoboWash uses a device similar to a fan to blow off the dust accumulated on the glass surfaces.
Who sets up the RoboWash to work?
The RoboWash is operated by the bridge personnel that starts and stops it. This robot does not have the capacity to start moving autonomously, based, for example, on sensors that monitor the weather conditions. It is the bridge personnel that must “tell” the robot to work when the bridge is free of road hazards, collisions, maintenance work, high level winds and any other condition that can interfere with its routine. However, the RoboWash is embedded with sensors that monitor the level of transparency of the glass and the amount of water that is present on its surface. Through these parameters, the RoboWash can recognize the ideal conditions for cleaning the glass.
The RoboWash is programmed to operate only in the safest conditions. For example, in case of high winds exceeding 50 Km/hr. (31 mph), the robot automatically terminates its routine and returns to its parking area. The robot has also the capability of calculating the amount of energy needed to reach the next recharging station. The stations are spaced 200-meters (656 ft) apart from one another along the rails.
It might be of interest to know that the RoboWash is equipped with a system that keeps the robot at a consistent distance from the glass panels of the sound barriers as it rides on the rails. The robot has therefore the ability to compensate for geometrical misalignments that may occur over time because of structural settlements and/or temperature changes, and/or other causes.
Can you explain how the RobotInspection functions?
The fixed and retractable sections of the RobotInspection monitor the outer surface of the steel box girder, which has an elliptical shape, by taking approximately 20000 pictures over the 30.000 m2 (322,917 sq. ft) of outer surface of the girder. The RobotInspection has the ability to take up to 25000 photos in a few days if weather and light permit.
The retractable beam is equipped with 3 cameras that have the capacity to scan the full outer surface of the steel girder (Pic #8). Scanning proceeds from the top level to the bottom level of the girder, which can only be reached when the retractable beam is fully extended. Essentially the RobotInspection works as a scanner taking photos of the outer surface of the steel box girder. Each photo covers a surface of approximately 1 m2 (11 sq. ft).
By analyzing the photos taken by the RobotInspection, bridge maintenance expert personnel can detect early signs of deterioration, such as paint flacking and/or steel corrosion. They can also examine the conditions of welding and connections. What sets this monitoring system apart from conventional inspection methods is the sheer amount of information collected and, even more importantly, the total objectivity of data. When photos are compared over time, there is total consistency of information due to the fact that photos are taken by the same equipment, at the same distance, and at the same angle. This level of data accuracy, consistency and repeatability cannot be achieved by drones or by inspections carried out by individuals, whose reporting always contains subjective elements of evaluation. Even if inspections are carried out by the same individual, this individual cannot guarantee that two or more reports will not be somehow affected by his, or her, subjectivity.
Does the RobotInspection have other functions in addition to scanning the outer bottom of the steel girder?
Yes, the RobotInspection can be equipped with an additional retractable beam that is connected to the retractable section of the main beam. The main beam is a huge structure (see Pic #9) that can carry up to 80 kg (176 lbs.) on its end. The additional beam has the ability of moving toward the surface of the steel girder to the point of touching it. It is designed to carry specialized instruments, such as 3D camera and ultrasound sensors that can provide in-depth information of steel imperfections. Ideally, in the future, the additional beam could also be equipped with instruments for painting and touching up.
The additional beam is designed to be used ad hoc. For example, if pictures taken by the main beam show 3 or 4 anomalies in the girder’s steel surface, then the owner has the capability of using the additional beam to evaluate these anomalies. If one of these anomalies remains questionable after the second inspection, then it is time to send an inspector. As a result, the robot has reduced the use of inspectors to a bare minimum, thus lowering costs and risks.
How frequently does the RobotInspection operate?
It is the bridge owner, ASPI (Ed. Note: ASPI is the largest Italian toll road operator, managing a network of 3000 km/1,864 miles in Italy) that decides on the frequency of use of the RobotInspection. Based on my knowledge, this robot operates from one to two times per year.
It takes a few days for the RobotInspection to complete the full inspection of the continuous girder. This time varies depending on weather conditions. The robot is equipped with sensors that stop its functioning in conditions of extreme weather, such as heavy rain or wind gusts of more than 15 meters/second (34 miles/hr.). The RobotInspection also stops working if the light is not sufficient to take pictures. Having a memory, the robot resumes operating from where it stopped. This ability is also present in the RoboWash
How is data gathered by the RobotInspection processed and stored?
The large number of 2D pictures taken by the RobotInspection are sent in real time to the data base of the bridge’s Control Center, which is equipped with a custom-designed software that contains algorithms for data analysis and storage.
The RobotInspection is considered part of the monitoring system of the bridge, which also encompass more than 240 sensors that are embedded in the bridge structure and monitored by Seastema (see LINKS). These sensors include 70 inclinometers, 50 accelerometers, and 50 extensometers.
What can you say about the maintenance program for the RobotInspection?
It is part of the overall maintenance program for the bridge. In addition to ordinary maintenance, before the robot starts its round of inspections, the bridge operator must go through a check list, similar to what happens when an airplane takes off. The robots are parked in a dedicated area. Before they start operating, the bridge operator must reach this area and go through a check list, similar to what happens when an airplane takes off.
Can you talk about main challenges encountered in the design and construction of the two robots?
There were many challenges for sure. First, the San Giorgio bridge is the replacement of a heavily trafficked urban bridge in Genoa. Due to the collapse of the previous bridge, transportation of goods going in and out the harbor of Genoa was delayed, trucks had to drive through villages and small towns, which created all sort of problems. The situation was not sustainable. It was essential to build the new bridge as soon as possible. Time constraint was definitely a challenge that extended from the construction of the bridge to the construction of the robots.
We worked under a tight schedule, but also under the radar because everybody was paying attention to the construction of the San Giorgio bridge, at both local and national level. The collapse of the Morandi bridge with its tragic loss of life was such a huge tragedy that propelled a strong emotional need among the Genoese people, and the Italians, to have a strictly monitored state-of-the-art bridge as a replacement.
Envisioning a new, innovative technology is always a major challenge. We did not have one single reference project for the design of the robots. To my knowledge there are no bridges worldwide that have autonomous robots permanently installed on the deck. Usually, robots are fixed elements that work in interior, protected environments. On the other hand, for this bridge we had to design robots that move constantly and work outside, in the open air, and therefore are subject to a variety of ambient conditions, such as rain, hail and wind. This technological invention was subsequently patented by IIT.
Even though this invention originated from the IRU group, IIT did not have the capability to build robots at Technological Readiness Level 8 (TEL8), which is the level required for equipment installed in production plants. So, when we started designing the robots, we sought out companies whose specialties would have helped us. A pivotal role was played by INNSE Berardi (Camozzi Group – Brescia, Italy) (see LINKS) that led the project, handled the design and construction of the control part of the robots, and also assembled and installed them. INNSE Berardi set up a mockup in their plant (see Pic #10) where we could test the robots before installation over the bridge.
In the design process, we took the key decision to start from the most critical component, which is the support for the robots, I mean the mechanism that allows the robots to move and stand. In order to face this challenge, we brought in a reputable partner in SDA Engineering from Padua, Italy (see LINKS), which is specialized in the construction of roller coasters. So, essentially, we ended up designing two roller coaster rails placed longitudinally along the two edges of the deck. In doing so, we were definitively helped by the fact that the girder has no joints and runs continuously from abutment to abutment.
The deck of the San Giorgio bridge can sway significantly under the high winds that frequently occur in Genoa. This was an additional challenge in the design of the robots and their measuring instruments.
As it would be expected, safety issues were given top priority in the design. Between the various safety measures, we equipped the four robots with sensors that make them stop immediately if they come in contact with somebody that, for whatever reason, enters the highly protected area where they operate. These features are called “Cognitive Mechatronics”, systems that provide the robots with the capability of making decisions, such as stopping a task depending on environmental conditions.
Finally, a considerable challenge entailed creating a dedicated code for the so-called secondary structure entailing the robots and implementing it within the Italian bridge construction code. This code does not encompass the presence of large moving objects that are permanently installed on a bridge. The bridge’s certification body had to work hard in order to create an appendix for the robots, as secondary structures to be included in the bridge construction code and within its safety requirements.
You have spoken of Camozzi Group and SDA Engineering. Could you go through the entire team that worked on the robots’ project?
The robots are definitively the result of a team effort that involved people from several companies having cutting-edge knowledge and competence in their field.
In addition to Camozzi Group and SDA Engineering that I mentioned before, the team included UBISIVE (see LINKS) from Civitanova Marche that created the man-machine software interface, Marche Polytechnic University (see LINKS) that envisioned and developed the Artificial Intelligence applications, Valeri Vanni consulting (see LINKS) that was in charge of certification of conformity with the Italian bridge construction code and safety regulations.
Essential team members were also AMS – Advanced Mechanical Solutions (see LINKS) that designed the main retractable beam of the RobotInspection and Ingersoll (see LINKS), which is part of the Camozzi Group.
In cooperation with the University of South Carolina and VX Aerospace Corporation, Ingersoll built the RobotInspection’s beams in fiber reinforced polymer having the high-rigidity / low-weight ratio that was requested by the bridge designer. The beams are actually carbon fiber, aerospace-type structure. Ingersoll used a 3D equipment called MasterPrint 3X that allows programming, simulating, 3D printing and milling large composite parts in a single piece. This equipment reduced the overall lead time for the construction of the two RobotInspections from months to weeks, and played an essential role in shortening the construction schedule. From the U.S. the composite beams were air freighted to Milan, Italy.
We worked in a coordinated manner with the General Contractor, PerGenova consortium of two companies: Webuild (see LINKS) and Fincantieri Infrastructure (see LINKS), as well as with the structural designer, Italferr (see LINKS).
Can you provide any information about the costs of the project?
The IIT donated the concept and the design of the RobotInspection and the RoboWash to the city of Genoa. The design entailed the work of 2 people over a period of 18 months. It is important to underscore that Renzo Piano also donated the design of the bridge to his native city of Genoa.