Structural Crack Detection Using DPP-BOTDA and Crack-Induced Features of the Brillouin Gain Spectrum

Dongyu Zhang,Yang Yang,Hui Li,Jinlong Xu,Li Ni

doi:10.3390/s20236947

Abstract

Structural damage generally initiates in the form of structural cracks. Thus, developing efficient crack detection techniques is of great importance for the structural health monitoring. In this paper, a new crack identification method is proposed, which is based on the differential pulse-width pair Brillouin optical time domain analysis (DPP-BOTDA) technology and the irregular features of Brillouin gain spectrum (BGS) in the fiber due to structural cracks. The proposed method provides a new way to detect and quantify structural cracks without knowing the strain in the structure. First, the working mechanism of DPP-BOTDA is introduced to illustrate the reason that the DPP-BOTDA, compared to traditional BOTDA technique, can significantly improve the spatial resolution of distributed strain sensing, which is critical for structural crack detection. Then, the BGSs in the fiber with the presence of structural cracks, measured by the DPP-BOTDA, are numerically simulated, from which the crack-induced irregular features of the BGS are summarized. Based these irregular features, new structural crack detection and quantification methods are proposed, which are found to be independent of structural stain. Finally, an experiment is conducted on a simple supported reinforced concrete (RC) beam. The results demonstrate that by using the BGS measured by the DPP-BOTDA, the proposed structural crack identification method successfully detects the occurrence of structural cracks and relatively accurately predicts the crack widths.

Highlights

Important civil structures, such as dams, bridges, buildings, etc., play crucial roles in supporting normal operation of human society
The results demonstrate that by using the Brillouin gain spectrum (BGS) measured by the DPP-BOTDA, the proposed structural crack identification method successfully detects the crack locations and relatively accurately predicts the crack widths
We presented a new crack identification method, which combines the DPP-BOTDA technology with the crack-induced irregular features of the BGS in the fiber

Summary

Introduction

Important civil structures, such as dams, bridges, buildings, etc., play crucial roles in supporting normal operation of human society. With gradual deterioration of construction materials and environmental corrosion, the structures will be unavoidably damaged. The damages generally initiate in the form of structural cracks, which allow external corrosive materials (e.g., chloride ion) to penetrate deeper inside the structure, accelerating the structural damage progress. Developing efficient techniques that can monitor the initiation and evolution of cracks on the surface of and inside structures will be of great value to accurately access structural damage condition and ensure the safe operation of the structure. Traditional structural crack detection mostly relies on human vision inspection, which is time and labor consuming. Some nondestructive test (NDT) methods, such as piezoelectricity transducer (PZT) sensors [1,2] and eddy current-based technologies [3] etc., are effective to detect structural

Results

Discussion

Conclusion