On April 15, 2019, at approximately 3:00 in the afternoon, a structural fire broke out beneath the roof of the Notre-Dame Cathedral in Paris.
The tragic fire caused the main spire and roof of the building to collapse, causing extensive damage that will take a long time and considerable costs to repair.
The fire serves as a reminder of the importance and fragility of historic buildings.
We treasure historic buildings because they hold our history, accent our artistry, and declare our desire for eternal remembrance. However, maintaining buildings well beyond their intended lifetime is no small feat.
I recently explored this topic with Blake Miller for the Future of Living Podcast which you can listen to below.
Historic buildings are in a constant battle against the elements.
Notre Dame was undergoing substantial repairs at the time of the fire, in part, because air pollution caused corrosion. Many buildings built with earthen materials, such the mud-brick structures of Djenné, Mali, need continual masonry to prevent decay. Even vibration from cars and trucks in the vicinity slowly inches these structures towards irreparable damage.
So how can we think creatively about using IoT technologies to help historical buildings stand the test of time?
In a facilities management world where the normal course of operations in preserving the asset is to maintain it until the end of its useful life, the management of historical structures requires a different approach. It is not acceptable to see a building though to obsolescence and then tear it down and start over. The very nature of these buildings and what draws people to them is the fact that they have been around for a long time and have historical significance.Casey Cluff, Arizona State University
A Tale of Two Buildings
At first glance, the Torre Aquila and Green Building couldn’t be more different.
The former was built during the 13th century as part of the Buonconsiglio Castle, and originally served as a defense tower.
The latter is a relic of more recent history: the surge in popularity of Brutalist architecture during the late 1950’s and 1960’s.
However, the operators of both buildings have used wireless sensor networks to protect the landmarks they safeguard.
The Torre Aquila
The exterior of the Torre Aquila may be demure, but inside are the brilliantly painted frescos, the “the Cycle of the Months.” The painted walls offer insight into life in the region during the 14th century, and attract thousands of visitors each year (Buonconsiglio).
The project started when the Municipality of Trento, where the Torre Aquila is located, submitted a proposal to build a road tunnel near the tower.
The initial construction, compounded by the pollution and vibration from the cars that followed, posed a threat to the structure and the frescos inside. The looming danger motivated the tower’s manager to install a monitoring system that would warn them of adverse conditions (Zonta et al.).
The Conservancy preferred a wireless sensor network instead of a cable-based network because cables would detract from the space’s allure. They installed three types of sensors: deformation sensors, environmental sensors (temperature, humidity, light), and accelerometers. A research team custom designed all of the sensors to meet the special battery and lifespan requirements of the building.
Now the frescos are under the watchful eye of dozens of sensors that alert the facilities’ team of lurking dangers.
The MIT Green Building
The MIT Green Building, the tallest building in Cambridge, Massachusetts, formidably juts out of the skyline. Standing 21-stories tall, it’s the perfect site to research how ambient vibration monitoring can help preserve tall structures.
The Green Building has faced a series of challenges over the course of its history. Shortly after opening, a series of glass-shattering events (literally), required that tall 284 of the building’s windows be replaced.
The building’s proximity to the Charles River, which sprayed gusts of wind strong enough to rip off a person’s glasses (William R. Dickson Oral History Project), also posed issues. Because of this, the doors and entryways had to be re-designed to allow for safe entry.
But what would happen to the building under more extreme circumstances like an earthquake? With climate change increasing the frequency and devastation of extreme weather events, researchers sought answers.
In contrast to the team at the Torre Aquila, the MIT research team focused solely on vibration.
They developed a monitoring system that collected data from 36 accelerometers spread throughout the building, and combined it with weather data, such as wind speed. They plugged that data into a high-fidelity finite element model that incorporated other relevant variables, such as “the strength and density of concrete walls, slabs, beams, and stairs in each floor (MIT News).”
Simulations demonstrated how a range of events, from a truck passing by to an earthquake, would affect the building’s stability. While the team hopes that similar systems can be installed in structures globally, there are factors stalling mass adoption, such as cost.
When can we expect to see all historical buildings outfit with wireless sensor networks?
Improvements in battery technology should help get us there faster. So, too, will the availability and ease of use of software that conducts finite element analysis to study building behavior.
These two factors, combined with more off-the-shelf hardware well suited for building use cases, will help make WSNs an attractive, affordable option for protecting our heritage.