Health Monitoring of Bolted Spherical Joint Connection Based on Active Sensing Technique Using Piezoceramic Transducers

Jing Xu; Chenyu Wang; Hongnan Li; Chunwei Zhang; Jiajia Hao; Shuli Fan

doi:10.3390/s18061727

Health Monitoring of Bolted Spherical Joint Connection Based on Active Sensing Technique Using Piezoceramic Transducers

Sensors (Basel). 2018 May 28;18(6):1727. doi: 10.3390/s18061727.

Authors

Jing Xu^{1

2}, Chenyu Wang³, Hongnan Li^{4

5}, Chunwei Zhang⁶, Jiajia Hao⁷, Shuli Fan⁸

Affiliations

¹ School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China. jingxu180@qut.edu.cn.
² State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China. jingxu180@qut.edu.cn.
³ Department of Mechanical Engineering, University of Houston, Houston, TX 77004, USA. cwang53@uh.edu.
⁴ State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China. hnli@dlut.edu.cn.
⁵ College of Civil Engineering, Shenyang Jianzhu University, Shenyang 110168, China. hnli@dlut.edu.cn.
⁶ School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China. zhangchunwei@qtech.edu.cn.
⁷ School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China. haojiajs@hotmail.com.
⁸ State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China. shuli@dlut.edu.cn.

Abstract

Bolted spherical joints are widely used to form space steel structures. The stiffness and load capacity of the structures are affected by the looseness of bolted spherical joint connections in the structures. The looseness of the connections, which can be caused by fabrication error, low modeling accuracy, and "false twist" in the installation process, may negatively impact the load capacity of the structure and even lead to severe accidents. Furthermore, it is difficult to detect bolted spherical joint connection looseness from the outside since the bolts connect spheres with rods together from the inside. Active sensing methods are proposed in this paper to monitor the tightness status of the bolted spherical connection using piezoceramic transducers. A triangle-on-triangle offset grid composed of bolted spherical joints and steel tube bars was fabricated as the specimen and was used to validate the active sensing methods. Lead Zirconate Titanate (PZT) patches were used as sensors and actuators to monitor the bolted spherical joint tightness status. One PZT patch mounted on the central bolted sphere at the upper chord was used as an actuator to generate a stress wave. Another PZT patch mounted on the bar was used as a sensor to detect the propagated waves through the bolted spherical connection. The looseness of the connection can impact the energy of the stress wave propagated through the connection. The wavelet packet analysis and time reversal (TR) method were used to quantify the energy of the transmitted signal between the PZT patches by which the tightness status of the connection can be detected. In order to verify the effectiveness, repeatability, and consistency of the proposed methods, the experiments were repeated six times in different bolted spherical connection positions. The experimental results showed that the wavelet packet analysis and TR method are effective in detecting the tightness status of the connections. The proposed active monitoring method using PZT transducers can monitor the tightness levels of bolted spherical joint connections efficiently and shows its potential to guarantee the safety of space steel structures in construction and service.

Keywords: Lead Zirconate Titanate (PZT); active sensing technique; bolted spherical joint connection; space steel structures; tightness status; time reversal method; wavelet packet analysis.