采用贴附法将一根玻璃纤维增强塑料(GFRP)单芯应变传感光缆埋设于钢筋混凝土试件的中间部位, 对混凝土内部应变进行分布式测量。考虑在温度和外加应变的作用下, 光纤中的背向布里渊(Brillouin)散射光将发生频移, 使用光时域反射仪(OTDR)对反射光信号进行了分析。研究了混凝土凝固过程中应变的变化, 结果表明: 混凝土试件浇筑完成当天应变变化明显, 应变变化趋势与试件内部温度相似, 试件内部应变主要受水泥水化热的影响。试件凝固后, 通过外力作用使得混凝土试件在纵向中心轴上产生平均宽度为6 mm的裂缝。检测裂缝出现前后试件的应变变化, 发现裂缝出现后试件内部应变明显变大, 共发现3个应变峰值。通过应变峰值位置的分析, 可判断裂缝的出现位置与方向。实验显示, 利用背向Brillouin散射的分布式应变检测技术可较好地实现混凝土应变的分布式测量。

One Glass Fiber Reinforced Plastic (GFRP) single core strain sensing cable is buried in a concrete specimen to measure the strain distribution. As the Brillouin backscattering center frequency will shift on the basis of effects of temperature and strain, the reflection signals are analyzed by an Optical Time Domain Reflectometer (OTDR). The strain variation in the solidification process of concrete is investigated. The strain monitoring results indicate that the strain variation is very obvious at the day when concrete pouring is completed. The trend of strain variation is similar as the temperature variation, which indicates that the strain variation of the concrete specimen during the concrete solidification process is mainly caused by the heat of concrete hydration. After the concrete solidification, a crack with an average width of 6 mm is appeared on the longitudinal center line of the concrete specimen by the external force. The strain variation is measured before and after the cracks appear, the results demonstrate that the strain variation is visibly improved after the crack, and there are three strain peaks in the specimen. By analysis of the strain peak position, the position and direction of the crack can be obtained. Thus, based on the Brillouin backscattering strain detecting technology, the distributed measurement of the concrete strain has been realized.