光纤光栅传感器对预应力锚索的受力监测

预应力锚索的受力状态监测特别是锚索内应力分布的监测是目前工程领域一大难题。本文提出将准分布式光纤布拉格光栅（FBG）内嵌至锚索材料-钢绞线中心丝的技术，以实现对其受力状态及应力分布进行监测。基于此技术，结合FBG监测原理和锚索锚固理论，以锚索锚固长度、FBG布设位置及数量为主要变化参数，设计了FBG自感知钢绞线材料并将其浇筑于钢管内作为锚索模型试件；并对FBG自感知钢绞线材料进行张拉标定试验和钢管锚索拉拔试验。张拉标定试验表明，内嵌于钢绞线中心丝材料中的准分布式FBG传感器成活率为100％，应变灵敏度集中在0.0012，应变-波长的拟合度皆超过0.999。拉拔试验结果表明，内嵌式FBG传感器可有效监测全长粘结型锚索轴力分布规律；且传感器可实现对锚固段、自由段应力传递规律的定点监测；为锚索浇筑长度的设计、张拉应力的补充提供了计算依据。

Study on Monitoring Performance of Embedded FIBER Bragg Grating Sensor for Prestressed Anchor Cable Construction Tension

Monitoring the stress state of prestressed anchor cable, especially the stress distribution in the anchor cable, is a difficult problem in the engineering field at present. In this paper, the technology of embedding quasi distributed fiber Bragg grating (FBG) into the center wire of anchor cable material steel strand is proposed to monitor its stress state and stress distribution. Based on this technology, combined with the FBG monitoring principle and the anchor cable anchoring theory, the FBG self sensing steel strand material is designed and poured into the steel pipe as the anchor cable model specimen with the anchor cable anchoring length, FBG deployment position and quantity as the main variation parameters; Tension calibration test and steel pipe anchor cable pull-out test were carried out for FBG self sensing steel strand material. The tension calibration test shows that the survival rate of quasi distributed FBG sensor embedded in the center wire material of steel strand is 100%, the strain sensitivity is concentrated at 0.0012, and the fitting degree of strain wavelength is more than 0.999. The pull-out test results show that the embedded FBG sensor can effectively monitor the axial force distribution of the full-length bonded anchor cable; The sensor can realize the fixed-point monitoring of the stress transfer law of the anchorage section and the free section; The calculation basis is provided for the design of anchor cable pouring length and the supplement of tension stress.