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

Iwao Matsuya,Fumiya Matsumoto,Ikuo Ihara

doi:10.3390/s150717000

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.

Highlights

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
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

Summary

Introduction

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. In this building, the seismically isolated layer is arranged between the ground and the first floor. 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

Methods

Results

Conclusion