Sensors report on the state of the building

Sensors report on
the state of the building

Engineers from Aarhus University are the first in the world to predict the durability of buildings and detect construction damage before it becomes visible to the naked eye.

Small sensors can collect information about vibrations in buildings and predict damage and collapse with greater accuracy than ever before.

By registering micro-vibrations with sensors, a research group from Aarhus University has developed a new method for monitoring the condition of buildings and other structures. The method is internationally ground-breaking and it could be of major significance for the construction industry in the future.

”Vibrations in a building can provide quite a lot of information about the properties of the construction. By using small sensors to gather information, we are able to predict how a building is doing a long time before the visible damage symptoms occur,” explains Rune Brincker, professor at Aarhus University.

It is the first time that researchers have developed a secure and reliable method for a so-called vibration based condition monitoring of buildings.

Analysis of vibrations reveals damage to the construction
Small vibrations occur all the time in all buildings. They are caused by general seismic activity in the ground surface and, by wind and they contribute to a continuous degradation of the construction.
So far researchers have not been able to monitor degradation and thereby predict the durability of a building, explains Rune Brincker.

”Fundamentally we know very little about how buildings are doing and therefore it is very difficult to predict their durability. We carry out inspection and maintenance programmes and, naturally, we carry out repairs when we discover visible damage. But we do not have any procedures for ensuring that we find that damage,” he says.

The durability mystery
Most of the buildings in the world were built within the last 50-100 years during a historic building boom. But nobody has been able to solve the mystery of their durability, explains Rune Brincker.
”Our bridges, dams and houses are relatively new. Many of them are still doing well but we know for certain that they will not last forever. The question is: how long will they last? That would be very valuable information,” says Rune Brincker.

With the new monitoring method and by analysing a building’s vibration pattern or its so-called vibration characteristics, the researchers are able to evaluate the building’s condition and predict its durability.

Detects cracks, frost damage and rust
The researchers have developed the first prototype of a system that is able to register the vibrations in a building via sensors. A computer with specially designed software collects and analyses data from the sensors and identifies incipient damage very precisely.

This damage may be cracks or other significant deteriorations of the construction such as frost damage in concrete. But it can also be rust in reinforcing bars or bridge wires that lead to the beginning of loss of bearing capacity.

The system can also be used for bridges as well as wind turbines and large structures.

Could provide large savings in the building industry
The researchers’ new method for monitoring buildings focuses primarily on safety. But the technology also has significant potential for savings in the building industry in that it contributes to reducing the use of materials.

"Today we have to oversize our buildings to prevent failure and fatigue in the construction. It is a strategy that we have used because we have lacked anything better but it has an extreme effect on raising the price of construction,” explains Rune Brincker.

The researchers expect that they will be able to reduce the use of materials by half or more in the long term and instead carry out continuous repairs and maintenance.