结构裂缝的分布式光纤监测方法及试验研究

结构裂缝监测是评估结构安全性的重要依据之一,分布式光纤裂缝监测技术可有效避免点式检测空间不连续造成的漏检现象,且易于实现自动化监测。该文提出了布里渊光频域分析计（BOTDA）结合斜交光纤组的裂缝监测方法,通过几何分析得到了光纤应变和裂缝宽度及开展方向的理论模型,并采用标定试验建立了由光纤测试应变反算裂缝宽度及开展方向的数值方程。同时开展了光纤裂缝传感器标距和预拉力大小对测量精度影响的试验研究,并标定了300mm标距的光纤裂缝传感器实测应变和裂缝宽度及夹角的定量关系。最后通过裂缝模拟试验对裂缝开展进行了跟踪监测,结果表明斜交光纤组能有效得到光纤与裂缝之间夹角值并实时监测裂缝宽度变化。

Cracking Monitoring Method and Experiment with Distributed Fiber Sensor

Cracking monitoring provides an important way to evaluate structural safety.Cracking monitoring method based on distributed optical fiber sensor can effectively avoid undetected phenomenon existed in point-wise test method,and it can run automatically.A theoretical model of cracking monitoring based on obliquely intersected fibers and Brillouin Optical Time Domain Analysis（BOTDA） is introduced,and the numerical equation among fiber strain,crack width and crack angle is established by the calibration experiment.The experiments are also carried out to study the performance of different kinds of cracking sensors with different gauge length and pretension.The quantitative relationship between optical fiber measured strain and crack（including width and angle） is established for the 300 millimeter crack sensor.The cracking simulation test proved that this new method can effectively record the width and the angle of cracks during the whole cracking process.