Structural Health Monitoring
Structural health monitoring is the process of implementing a damage identification strategy by monitoring changes to the material and geometric properties of civil, aerospace, and mechanical engineering infrastructure. Structural health monitoring has many benefits.
Owners of a structure have little information about the real state of the materials, the real loads acting on the structure, and about its ageing. When making decisions, the owners have no other choice than to assume the worst to keep the structure on the safe side. Monitoring gives the owner the ability to make informed decisions based on factual data. By reducing the uncertainty associated with the insured risk it can also reduce the insurance costs.
Structural health monitoring reduces uncertainties
Structural health monitoring discovers hidden structural reserves
Most structures are in far better condition than expected. When taking advantage of over-design, better material properties, and synergetic effect it is possible to extend the lifetime or load-bearing capacity of a structure safely without any intervention. By doing this, the repair and replacement costs can be delayed.
Structural health monitoring discovers deficiencies in time and increases safety
Some deficiencies cannot be found by visual inspection or modelling. In these cases, it is important to undertake appropriate remedial or preventive actions before it gets worse. Repairing such a deficiency will be much cheaper and will cause less disruption to the use of the structure if it is done at the right time. Monitoring a structure gives permanent and reliable data to improve the safety of the structure and its users.
Structural health monitoring ensures long-term quality
Monitoring a structure provides continuous and quantitative data which helps in evaluating the quality of the structure during construction, operation, maintenance, and repair, thus eliminating the hidden costs of non-quality. Many of the damages and defects to a structure are build in during the process of construction. However, many of them will not be visible till years later, when repair is no longer covered by the contractor’s warranty. This makes repair much more expensive.
Monitoring data can increase the quality of decisions by providing reliable and unbiased information, therefore allowing owners to spend on maintenance and reconstruction when required and not only when budget allows it.
Structural health monitoring allows structural management
Structural health monitoring increases knowledge
Knowing how a structure performs in real conditions, will lead to performance-based designs in the future. This will bring about structures with increased reliability and performance, which are also cheaper, safer, and more durable. Investing in monitoring will lead to savings later in the project by discovering weaknesses in time and optimizing the design.
Project: Genoa bridge
We all remember August 14, 2018, the day the bridge in Genoa tragically collapsed because it structurally could not handle the weight of present-day traffic needs. Due to the daily importance of the bridge, it was clear a new bridge would need to be built quickly. The designers of the bridge immediately decided to employ some form of structural health monitoring to ensure safety.
Renzo Piano designed the new bridge as a gift to his hometown. Local businesses managed to build the bridge in a very short time. Which was needed because the Genoa bridge has a huge economic value since it is part of the main traffic routes of northern Italy. Not only does it connect Genoa to Milan, but it also connects Italy to France.
On April 28, 2020, the last part of the new bridge was placed. The bridge was named the Ponte San Giorgio, after Saint George, one of the patron saints of Genoa. According to engineer Tartaglia, the bridge should be "The safest and most monitored bridge in Europe." And in that monitoring, Somni could play an important role!
Somni has equipped each pillar and pillar foundation of the bridge with two highly sensitive tilt sensors, which monitor the misalignment of the pillar’s day and night. This way, both the foundation of each pillar and the pillars themselves are monitored with respect to settlement of the soil, traffic loads, wind and temperature and all other conditions that could affect the health of the structure.
The main reason for choosing fiber optic sensors in this application is the very high reliability of these sensors and their unmatched lifetime. Electrical sensors, and the electrical cables required for the sensors, are known to be much more fragile than fibers and fiber optic sensors. The decision to install only fiber optic cables, connections, and sensors in all the hard-to-reach places was therefore made quickly.
A quick demonstration
In this video, the working principle of three sensors are demonstrated on a quay wall.
A displacement sensor is used for crackmonitoring, and two tilt sensor are used to measure the defeclection forwards and sideways.