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Smart Structures and Systems
  Volume 21, Number 1, January 2018 , pages 027-35

BOTDA based water-filling and preloading test of spiral case structure
Heliang Cui, Dan Zhang, Bin Shi and Shusheng Peng

    In the water-filling and preloading test, the sensing cables were installed on the surface of steel spiral case and in the surrounding concrete to monitor the strain distribution of several cross-sections by using Brillouin Optical Time Domain Analysis (BOTDA), a kind of distributed optical fiber sensing (DOFS) technology. The average hoop strain of the spiral case was about 330 u e and 590 u e when the water-filling pressure in the spiral case was 2.6 MPa and 4.1 MPa. The difference between the measured and the calculated strain was only about 50 u e. It was the first time that the stress adjustment of the spiral case was monitored by the sensing cable when the pressure was increased to 1 MPa and the residual strain of 20 u e was obtained after preloading. Meanwhile, the shrinkage of 70 ~ 100 u e of the surrounding concrete was effectively monitored during the depressurization. It is estimated that the width of the gap between the steel spiral case and the surrounding concrete was 0.51 ~ 0.75 mm. BOTDA based distributed optical fiber sensing technology can obtain continuous strain of the structure and it is more reliable than traditional point sensor. The strain distribution obtained by BOTDA provides strong support for the design and optimization of the spiral case structure.
Key Words
    BOTDA; distributed optical fiber sensing; strain distribution; spiral case; water-filling; preloading; hydraulic structure
Heliang Cui: School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;
POWERCHINA Huadong Engineering Corporation Limited, Hangzhou 311222, China
Dan Zhang and Bin Shi: School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
Shusheng Peng: Zhejiang Huadong Engineering Safety Technology Co.,Ltd., Hangzhou 311222, China

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