【摘要】 基于光纤拉断引起菲涅尔反射机理,考虑大型工程结构多处随机裂缝监测的需求,利用普通商用光时域反射计(OTDR)提出了可同时探测多处随机裂缝的多段分布式光纤裂缝监测系统设计方法。该系统由多区段传感光路和传输光路组成,混凝土开裂时光纤被拉断,使用OTDR识别光纤中的菲涅尔反射以确定裂缝位置。其次,分析了影响该系统监测裂缝数目的主要因素为光纤耦合器的耦合比、OTDR的动态范围以及光纤断点处菲涅尔反射峰值。结果表明,该系统对于普通商用OTDR理论上最多可探测到49个断点。在此基础上,设计制作了钢筋混凝土受弯构件裂缝演化规律的多段分布式光纤裂缝监测系统,使用普通商用OTDR成功地监测到受弯构件加载过程中的多个随机裂缝的演化过程,证明了该系统实际应用的可行性和有效性。更多还原

【Abstract】 A multi-line distributed fiber optic sensor system was developed to detect the cracks on concrete structures.Conventional commercial Optical Time Domain Reflectometer(OTDR) was used in this system and more than one random crack can be detected.The system comprises light carrying and sensing parts.The sensing fiber would be broken by crack,and the corresponding Frenel reflection on the fiber would be identified by OTDR.The coupling ratio of fiber optic coupler,the dynamic range of OTDR and the Frenel reflection value of optic fiber influences the maximum crack numbers detected by this system,research results shows it is about 49 theoretically.An experiment involving the monotonic loading on a reinforced concrete beam to failure is conducted,and the sensing system is applied to sensing the crack evolution.The feasibility and efficiency of the system in civil engineering application is proved by this experiment.更多还原