With New Computational Model, Buildings May “Sense” Internal Damage

With New Computational Model, Buildings May “Sense” Internal Damage
M. Nafi Toksöz, professor in the Department of Earth, Atmospheric and Planetary Sciences (EAPS); Oral Buyukozturk, professor in the Department of Civil and Environmental Engineering (CEE); and Hao Sun, a postdoc in CEE. The Green Building, behind them, has 36 accelerometers that record vibrations and movements on selected floors, from the building’s foundation to its roof. Photo: Jose-Luis Olivares/MIT

MIT scientists have developed a computational model that makes sense of ambient vibrations. It raises some features in the noise that give indications of a building’s stability. According to scientists, this new model may use to control building a building over time for signs of damage or mechanical stress.

Scientists tested this model on MIT’s Green Building the building was made from assisted concrete. In 2010, Toksöz and others at MIT worked with the United States Geological Survey to outfit the Green Building with 36 accelerometers. The accelerometer record vibrations and movements on selected floors, from the building’s foundation to its roof.

Professor Oral Buyukozturk said, “These sensors represent an embedded nervous system. The challenge is to extract vital signs from the sensors’ data and link them to health characteristics of a building, which has been a challenge in the engineering community.

To do this, scientists develops a computer simulation of the Green Building in the form of a bounded element model. After that, they plugged various parameters into the model. The parameters are strength and density of concrete walls, slabs, beams, and stairs on each floor.

With New Computational Model, Buildings May “Sense” Internal Damage
CEE postdoc Hao Sun sits in a stairwell in the Green Building. On the right attached to the ceiling is one of the accelerometers used to monitor the building.

This new computational model uses a lot of assumptions about the building’s material. It may not correspond exactly to the structure.

Buyukozturk said, “So we are updating the model with actual measurements. Through this, we will able to give better information about what may have happened to the building.”

Once the model gets ready, scientists will able to introduce an excitation in the simulation. For example, a truck-like vibration and the model would predict how the building and its various elements should respond.

Scientists extract data from the Green Building’s accelerometers to precisely predict a building’s response to surrounding vibrations. Through this, scientists can look for features that associate with building’s rigidity or other health indicators. To effective do this, scientists then developed a new method with the seismic interferometry concept. This method describes changes in vibration’s pattern changes as it travels from the ground level to the roof.

Buyukozturk explains, “We look at the foundation level and see what motions a truck. For example, caused there, and then how that vibration travels upward and horizontally, in speed and direction.

Scientists then include this information in their model of the Green Building. They ran the model multiple times, each time with a set of measurements taken by the accelerometers at a given point in time. In all, the group plugged into the model vibration measurements that were taken continuously over a two-week period in May 2015.

With New Computational Model, Buildings May “Sense” Internal Damage
Hao Sun holds an example of a sensor. “I would envision that, in the future, such a monitoring system will be instrumented on all our buildings, city-wide,” says Sun. “Outfitted with sensors and central processing algorithms, those buildings will become intelligent, and will feel their own health in real time and possibly be resilient to extreme events.”

Buyukozturk said, “We are continuously making our computational system more intelligent over time, with more data. We are confident if there is damage in the building, it will show up in our system.”

Although, the building is safe. But it is subject to quite a bit of vibration, particularly in the upper floors. The building built on soft soil is long in one direction and narrow in the other with stiff concrete walls on each end. Thus, it controls torsional movements and rocking, especially on windy days.

Scientists are now planning to check their computational model with experiments in the lab. They will study the effects of ambient vibrations, as well as how the structure responds to hammer strikes and other seismic stimuli. Scientists also building a large steel structure, about the size of a cellphone tower. Through this, they will conduct similar experiments that will ultimately help to refine the researcher’s computational model.

Lead author Hao Sun said, “I would envision that, in the future, such a monitoring system will be instrumented on all our buildings, city-wide. Outfitted with sensors and central processing algorithms, those buildings will become intelligent, and will feel their own health in real time and possibly be resilient to extreme events.”

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