Ground Sensors: The Future of Structural Integrity Sensing for Earthquake-Prone Areas

Recently, a group of researchers have successfully developed a structural sensing system consisting of ground sensors, battery-operated components, and remote servers. The sensors are capable of detecting early warning signs of structural collapse caused by earthquakes, such as small changes in tensile forces, shifts in foundation, and vibrations, and alert building occupants in real time through noise reduction and LED illumination. The sensing system aims to increase building safety and reduce fatalities during natural disasters, including earthquakes, tornadoes, hurricanes, storms, and floods, by providing an early warning system for integrated sensors to predict when damage is likely to set in. What challenges does structural integrity sensing face, what did the researchers develop, and how could it be used to save lives during earthquakes?

What challenges does structural integrity sensing face?

Man has been constructing buildings since the dawn of time, with some of the earliest structures dating as far back as 9000 BC. Throughout this history of architecture, building stability has always played a critical role, especially for structures that were meant to last the ages as a testament to civilisation. For example, the shape of the Pyramids of Egypt has provided an excellent degree of stability, allowing them to exist for thousands of years since their construction.

Of course, large triangles with wide bases will undoubtedly be very stable, but unfortunately, this type of building is not practical for modern life, especially in countries such as Korea and Japan, where space is a virtue. This is why modern skyscrapers are narrow, tall, and generally uniform in shape. 

Even though most buildings are given a solid foundation to sit on, natural disasters such as earthquakes and strong winds can see buildings collapse, especially structures that have begun to age. Thorough inspections of foundations and structural components can give engineers an idea of the condition of a building, but this process is often intense, requires vast amounts of engineering time, and can be extremely expensive. 

One major challenge in maintaining the structural integrity of buildings and infrastructure is the difficulty and expense of traditional inspection methods. These methods often require expensive equipment and highly trained personnel, making them impractical for widespread use. Furthermore, these inspections may not be able to detect certain types of damage or defects that can compromise the safety of the structure.

Fortunately, advancements in technology have made it possible to develop more efficient and accurate methods for structural integrity sensing. By using sensors and other monitoring technologies, engineers can continuously monitor the health of a structure and quickly detect any issues that arise. This can help prevent catastrophic failures and ensure the safety of the people who use these structures every day.

One solution is to install sensors into critical components of a building and stream the resulting data to some remote server. By analysing the data collected from such sensors, engineers can detect small changes in tensile forces, shifts in the foundation, and even vibrations throughout the structure. But the vast amount of data combined with the need for battery-operated components makes this an extremely difficult task to accomplish. 

Furthermore, the data needs to be interpreted by engineers to determine if the structure is genuinely at risk. For example, small seasonal variations can see slight shifts in the ground, and high winds can make buildings sway, but this alone would not be a sign of structural damage. 

Overall, integrating many sensors capable of detecting small changes while ignoring noise is challenging, and creating alarms that alert those in the building of a potential collapse in real time is simply not possible with current off-the-shelf technology.

Researchers create real-time structural sensors

In light of the continuing dangers posed by potentially dangerous structures (such as those in Turkey), researchers from Korea have recently unveiled a new structural sensing system that is easy to install, is entirely battery operated, and can alert those nearby of imminent danger without needing to have vast amounts of data analysed. 

The new sensors are installed at a distance of between 1m and 2m from each other and work together to detect minute changes in elevation and angle (as small as 0.03˚). The data gathered by these sensors is not streamed to a remote server but instead processed locally via on-chip algorithms, and this is used to distinguish between genuine signs of collapse and changes due to environmental conditions (such as temperature fluctuations, moisture etc.). 

If a sign of collapse is detected, an LED is illuminated so those nearby can visually see that the building is at risk. However, instead of using off-the-shelf LEDs, the researchers turned to a highly efficient optical lens technology to allow the LED to be visible from 100 meters away both day and night. 

 A photo of the installation site of the newly developed sensor in the lava cave. 

To ensure that the sensors can operate for extended periods, the researchers were able to reduce the power consumption of their solution by 50% compared to pre-existing options. As such, the new sensors can operate for an entire year on a single battery. In addition to this extended battery life, the sensors can also operate at temperatures from -30˚C to +80˚C, enabling them to work in most environments on Earth. 

Currently, the sensors have been deployed in several locations to test out their effectiveness, including in lava tubes, roads, mountainsides, and along high-speed rail lines. The researchers hope that over time, the sensor solution will be deployed in more critical environments, such as buildings and structures prone to collapse.

How can such sensors help save lives in the future?

One of the biggest dangers posed by earthquakes isn’t that they have the ability to level a city but that they do so without any notice whatsoever. Tornadoes and hurricanes can be predicted to some degree, with early warning sirens providing citizens some time to take shelter and prepare. Storms can be detected days in advance, and floods are often identified by areas of risk. But earthquakes are virtually impossible to predict, let alone create an early warning system, meaning that people can be in the worst places when they strike. In fact, if an earthquake could be predicted, people could just stand in the street and mostly avoid damage, as buildings would collapse with no one inside them, and people would fall to the ground if the shaking was intense enough.

However, buildings don’t just collapse during an initial earthquake; they can also collapse after the damage has occurred. During these times, people can go into buildings thinking they are safe, only to find that the building eventually collapses after a day or two. It is in these cases where sensors integrated into the structure that monitors for small changes could save lives. Thus, the sensors developed by the researchers in Korea could help to provide early warning signs of buildings before, during, and even after an earthquake.