混凝土中基于预埋式LPFG波长解调的耐久性健康监测

Embedded long-period fiber grating sensors for monitoring the steel corrosion in reinforced concrete structures

为了实现混凝土结构的耐久性健康监测,提出基于长周期光纤光栅(LPFG)折射率特性,将LPFG预埋入混凝土结构中,通过对LPFG的波长解调,实现钢筋锈蚀监测。钢筋发生锈蚀后,钢筋钝化层表面附近Cl-浓度的改变将影响钢筋周围混凝土的折射率,对LPFG进行波长解调并进行温度补偿,获知环境折射率变化进而判断钢筋的锈蚀程度。实验结果表明,钢筋锈蚀率达到12.6%时,对应的锈水折射率1.353 6仍小于LPFG可监测到的折射率范围,并实验获得了LPFG谐振波长漂移量与钢筋锈蚀率之间的对应关系。本方法无需化学试剂,全光纤化,能够准确地实现混凝土结构中钢筋锈蚀的早期至中期监测。

To realize the durability health monitoring of the concrete structures, a new technique based on the refractive index characteristic of long period fiber grating （LPFG）to measure the corrosion of steel on concrete structures is proposed in this paper. A notch-shaped pedestal is designed and a long period fiber grating is laid on the steel surface. With this method,the Cl^- concentrations of the steel resulting from the steel corrosion would be transformed into the refractive index of the long period fiber grating. The corrosion rate of steel could be obtained by analyzing the change of the spectrum,and then the steel corrosion depth could be measured. From the experiment , it is found that the corrosion rate reaches 12.6% ,and the surrounding refractive index changes to 1. 353 6 which is within the monitoring range of the LPFG. And the relationship between the wavelength shift and the corrosion rate is obtained. This measurement could be used to monitor the early to medium term corrosion of reinforcing steel in concrete structures.