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Ultrasonic Lateral Displacement Sensor for Health Monitoring in Seismically Isolated Buildings.

Matsuya I, Matsumoto F, Ihara I - Sensors (Basel) (2015)

Bottom Line: The transmitters are immobilized at a fixed point, whereas the receiver set-up is separately arranged on the opposite side.In order to improve measurement accuracy, a correction method that utilizes polynomial approximation is introduced.When five transmitters are arranged, their measurement range is easily extended up to ±60 mm with an accuracy of 0.7 mm.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka 940-2188, Niigata, Japan. matsuya@mech.nagaokaut.ac.jp.

ABSTRACT
An ultrasonic lateral displacement sensor utilizing air-coupled ultrasound transducers is proposed. The normally-distributed far field of an ultrasound transducer in a lateral direction is taken advantage of for measuring lateral displacement. The measurement system is composed of several air-coupled ultrasound transducers as a receiver and several transmitters. The transmitters are immobilized at a fixed point, whereas the receiver set-up is separately arranged on the opposite side. In order to improve measurement accuracy, a correction method that utilizes polynomial approximation is introduced. The difference between the corrected lateral displacement and the reference displacement is estimated to be 0.2 mm at maximum for the two transmitters system. A good responsiveness is demonstrated by conducting a dynamic response experiment. When five transmitters are arranged, their measurement range is easily extended up to ±60 mm with an accuracy of 0.7 mm. In both cases, the fluctuations to the measurement ranges show less than 1%. These results indicate that the developed sensor system is useful for measuring relative lateral displacement of a seismically isolated building in the field of structural health monitoring.

No MeSH data available.


Related in: MedlinePlus

(a) Seismically isolated building; (b) Enlarged view of the seismically isolated layer and installation of ultrasonic lateral displacement sensor.
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sensors-15-17000-f001: (a) Seismically isolated building; (b) Enlarged view of the seismically isolated layer and installation of ultrasonic lateral displacement sensor.

Mentions: Since the late 1990s, the number of seismically isolated buildings has been increasing with the purpose of preventing structural damage and ensuring safety in case of earthquakes [1,2,3,4,5,6,7,8]. If a large earthquake strikes a seismically isolated building, an isolated layer will absorb the bulk of the seismic motion energy leading to drastically different results when compared to a conventional building. Figure 1a shows a seismically isolated building. In this building, the seismically isolated layer is arranged between the ground and the first floor. The isolated layer consists of dampers and isolators that support the superstructure. The isolators are made of laminated rubber and work like a spring which allows a large horizontal displacement of the superstructure. The dampers reduce the displacement response of the superstructure. Although the movement of a conventional building with several stories has been measured at approximately 2 Hz during an earthquake, the dominant response of a seismically isolated building is reduced to around 0.1 to 0.5 Hz, which is similar to the displacement response of a high-rise building. The natural frequency of a seismically isolated building is generally determined by the damping ratio of the isolated layer. In addition, a large displacement between the superstructure and the ground, which is estimated to be approximately 200–300 mm for a relatively severe earthquake, is generated in the seismically isolated building. These characteristics of seismically isolated buildings reduce damage to structural/non-structural members and allow them to maintain their functionality after an earthquake. In the field of structural health monitoring (SHM), a significant amount of research about measuring the acceleration of the motion response of buildings has been reported [9,10,11,12,13,14], but direct measurements of the lateral displacement of seismically isolated buildings in real time are particularly valuable. If the lateral displacement of the isolated layer can be measured directly in real time, the deterioration of the laminated isolated rubber can then be evaluated appropriately. However, the maximum lateral displacement of the isolated layer of a seismically isolated building is extremely wide, and it varies case-by-case according to the characteristics of the isolator. Furthermore, the distance between the superstructure and the ground seems to vary in different buildings, depending on their design. Finally, the lateral displacement of the layer returns to the origin at the end of an earthquake, so we cannot evaluate the damage related to the maximum displacement. These factors have made the measurement of the lateral displacement of the isolated layer difficult for conventional sensors.


Ultrasonic Lateral Displacement Sensor for Health Monitoring in Seismically Isolated Buildings.

Matsuya I, Matsumoto F, Ihara I - Sensors (Basel) (2015)

(a) Seismically isolated building; (b) Enlarged view of the seismically isolated layer and installation of ultrasonic lateral displacement sensor.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541918&req=5

sensors-15-17000-f001: (a) Seismically isolated building; (b) Enlarged view of the seismically isolated layer and installation of ultrasonic lateral displacement sensor.
Mentions: Since the late 1990s, the number of seismically isolated buildings has been increasing with the purpose of preventing structural damage and ensuring safety in case of earthquakes [1,2,3,4,5,6,7,8]. If a large earthquake strikes a seismically isolated building, an isolated layer will absorb the bulk of the seismic motion energy leading to drastically different results when compared to a conventional building. Figure 1a shows a seismically isolated building. In this building, the seismically isolated layer is arranged between the ground and the first floor. The isolated layer consists of dampers and isolators that support the superstructure. The isolators are made of laminated rubber and work like a spring which allows a large horizontal displacement of the superstructure. The dampers reduce the displacement response of the superstructure. Although the movement of a conventional building with several stories has been measured at approximately 2 Hz during an earthquake, the dominant response of a seismically isolated building is reduced to around 0.1 to 0.5 Hz, which is similar to the displacement response of a high-rise building. The natural frequency of a seismically isolated building is generally determined by the damping ratio of the isolated layer. In addition, a large displacement between the superstructure and the ground, which is estimated to be approximately 200–300 mm for a relatively severe earthquake, is generated in the seismically isolated building. These characteristics of seismically isolated buildings reduce damage to structural/non-structural members and allow them to maintain their functionality after an earthquake. In the field of structural health monitoring (SHM), a significant amount of research about measuring the acceleration of the motion response of buildings has been reported [9,10,11,12,13,14], but direct measurements of the lateral displacement of seismically isolated buildings in real time are particularly valuable. If the lateral displacement of the isolated layer can be measured directly in real time, the deterioration of the laminated isolated rubber can then be evaluated appropriately. However, the maximum lateral displacement of the isolated layer of a seismically isolated building is extremely wide, and it varies case-by-case according to the characteristics of the isolator. Furthermore, the distance between the superstructure and the ground seems to vary in different buildings, depending on their design. Finally, the lateral displacement of the layer returns to the origin at the end of an earthquake, so we cannot evaluate the damage related to the maximum displacement. These factors have made the measurement of the lateral displacement of the isolated layer difficult for conventional sensors.

Bottom Line: The transmitters are immobilized at a fixed point, whereas the receiver set-up is separately arranged on the opposite side.In order to improve measurement accuracy, a correction method that utilizes polynomial approximation is introduced.When five transmitters are arranged, their measurement range is easily extended up to ±60 mm with an accuracy of 0.7 mm.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka 940-2188, Niigata, Japan. matsuya@mech.nagaokaut.ac.jp.

ABSTRACT
An ultrasonic lateral displacement sensor utilizing air-coupled ultrasound transducers is proposed. The normally-distributed far field of an ultrasound transducer in a lateral direction is taken advantage of for measuring lateral displacement. The measurement system is composed of several air-coupled ultrasound transducers as a receiver and several transmitters. The transmitters are immobilized at a fixed point, whereas the receiver set-up is separately arranged on the opposite side. In order to improve measurement accuracy, a correction method that utilizes polynomial approximation is introduced. The difference between the corrected lateral displacement and the reference displacement is estimated to be 0.2 mm at maximum for the two transmitters system. A good responsiveness is demonstrated by conducting a dynamic response experiment. When five transmitters are arranged, their measurement range is easily extended up to ±60 mm with an accuracy of 0.7 mm. In both cases, the fluctuations to the measurement ranges show less than 1%. These results indicate that the developed sensor system is useful for measuring relative lateral displacement of a seismically isolated building in the field of structural health monitoring.

No MeSH data available.


Related in: MedlinePlus