Crack Detection of Reinforced Concrete Member Using Rayleigh-Based Distributed Optic Fiber Strain Sensing System

Early detection of crack is critical for the maintenance of reinforced concrete (RC) structures. In this study, a distributed optical fiber (DOF) sensing system with Rayleigh Optical Frequency Domain Reflectometry (OFDR) technique was deployed to a member of RC structure in a full-scale laboratory experiment, which was subjected to a monotonic lateral load. With the aid of a high space resolution (up to 1 mm) and measurement accuracy (+/- 1 micro strain) interrogator (OSI-S by Semicon), continuous strain measurements inside of the RC member are elaborately implemented. The result of crack detection by the analysis of the measured tensile strain profiles is in excellent agreement with the visually observable cracks mapped during the test. This confirms the ability of the optical fiber inside of RC members to capture cracks on concrete surface. Moreover, the recognition of crack orientation and depth is accomplished by comparing strain measurements of optical fibers installed at multiple locations.

裂缝的早期检测对于钢筋混凝土（RC）结构的维护至关重要。在这项研究中，在一个足尺实验室实验中，将采用瑞利光频域反射计（OFDR）技术的分布式光纤（DOF）传感系统应用于一个钢筋混凝土结构构件，该构件承受单调侧向荷载。借助高空间分辨率（高达1毫米）和测量精度（±1微应变）的解调器（Semicon公司的OSI - S），精心对钢筋混凝土构件内部进行了连续应变测量。通过对测量的拉伸应变剖面分析得到的裂缝检测结果与试验期间绘制的肉眼可见裂缝高度吻合。这证实了钢筋混凝土构件内部的光纤捕捉混凝土表面裂缝的能力。此外，通过比较安装在多个位置的光纤的应变测量结果，实现了对裂缝方向和深度的识别。