用于钢绞线大应变测量的光栅传感技术研究

Research on the FBG sensing technology for large strain measurement of steel strand

降低光纤布拉格光栅(fiber Bragg grating,FBG)应变传感器的应变灵敏度是解决其量程小无法监测大应变问题的关键技术。为监测预应力钢绞线(特别是桥梁永久性构件的拉索、预应力混凝土)在施工及使用全过程的应力应变变化,本文提出螺旋倾斜式光栅复合技术,在实现预应力筋大应变监测的同时解决了裸光纤光栅易损坏、难以封装的难题;建立了光栅实测应变与钢绞线应变间的理论关系,通过不同倾角试验,测定光栅应变灵敏度的变化。试验研究结果表明,该方法有效降低了光栅应变灵敏度,从1.18pm/με降为0.88pm/με,实现了增大光栅应变测量量程的目的。

For reducing the strain sensitivity of FBG （Fiber Bragg Grating,FBG）,which is a key technology to solve failing large strain monitoring of small-scale.In order to prestressed steel strand （particularly permanent members of the cable in bridges,prestressed concrete） in the whole process of construction and use,the technology of bonding FBG spirally and slantingly was proposed.This method can realize big strain monitor of prestressing tendon,at the same time,the problem of being damaged easily and packaged difficultly of bare fiber grating was solved.The theory relationship between the measured strain of FBG and the actual strain of steel strand was established.Through the different helix angle tests,the strain sensitivity changes of FBG was measured.The experimental results show that this method can effectively reduce the strain sensitivity of FBG,which were decreased to 0.88 pm/με from 1.18 pm/με,and achieve the purposes of increasing the strain measurement range of FBG.