Crack detection in hydraulic concrete structures using bending loss data of optical fiber

Due to low tensile strength of concrete, seasonal temperature, shrinkage of concrete, and so on, many of hydraulic concrete structures experience cracking. An optical fiber–based approach is introduced to implement the crack detection in hydraulic concrete structures. The experimental and theoretical investigations on bending loss and time-domain reflection behaviors of optical fiber are performed. According to the bending loss mechanism of optical fiber, the monitoring method of hydraulic concrete crack is presented. First, the effect of optical fiber bending radius on optical loss is analyzed. The mathematical model between bending radius and optical loss is established. Then, the identification principle of concrete crack using bending loss data of optical fiber is studied. Considering the crack characteristics of hydraulic concrete structure, the arrangement forms of optical fiber, which are used to monitor the tension crack and hybrid crack in hydraulic concrete structure, are proposed. Finally, the relationship between crack development and optical loss is investigated using laboratory experiments with optical fiber.