A new flexible FBG sensing beam for measuring dynamic lateral displacements of soil in a shaking table test

Dong-Sheng Xu a, Jian-Hua Yin a, Zhen-Zhong Cao b, Yun-Long Wang b, Hong-Hu Zhu c,
Hua-Fu Pei a
a Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
b Institution of Engineering Mechanics, China Earthquake Administration, Harbin, China
c School of Earth Sciences and Engineering, Nanjing University, Nanjing, China

Source: Measurement Available online 21 June 2012

Fulltext link: http://dx.doi.org/10.1016/j.measurement.2012.06.007

In this paper, the design, validation, and application of a new flexible fiber Bragg grating (FBG) sensing beam are presented for effectively measuring dynamic lateral displacements inside soil mass in a shaking table test. The special flexible FBG sensing beam has been fabricated by employing a series of FBG sensors along with design of temperature compensation. Based on this design, equations of converting strains to lateral displacements are derived by using both differential and integral methods. Subsequently, the effectiveness of the FBG sensing beam has been verified in a shaking table test with non-contact laser displacement sensors (LDSs). The dynamic lateral displacements at different depths of the soil mass in the shaking table box throughout time history are calculated by differential and integral methods and compared with the results of LDSs. The comparison validates the measurement accuracy of the FBG sensing beam. Additionally, the Fast Fourier Transform (FFT) analysis result demonstrates that frequency measured by the sensing beam fits well with the results of traditional accelerometers and LDSs. Therefore, it can be concluded that the flexible FBG sensing beam is compatible with the stiffness of the soil and is capable of measuring dynamic lateral displacements with good accuracy in a shaking table test.

Fiber optic sensor; Fiber Bragg grating (FBG); Dynamic lateral displacement; Shaking table test

1. Introduction

2. Principle and design of the FBG sensing beam

3. Verification of the shaking table test

4. Conclusions


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