预张拉光纤布拉格光栅应变传递规律实验研究

Experimental Research on Strain Transfer Rules of Prestressing Fiber Bragg Grating

利用裸光纤布拉格光栅测量结构物表面应变,基于光纤层-胶结层-基体层的应变传递模型,从理论上分析了预张拉对应变传递率的影响,并通过实验进行了验证。利用预张拉光栅与未预张拉光栅同时测量了等强度梁正反两面的应变。实验中为排除黏贴长度及厚度的影响,采用LOCTITE点胶机控制滴胶量,得到应变随荷载变化的曲线,并与等强度梁理论应变值进行对比,得到应变传递率与荷载的关系曲线。结果表明,在测拉应变时,预张拉光栅的应变传递率高于未预张拉光栅的应变传递率,且两者都在96%以上;在测压应变时,预张拉光栅的应变传递率低于未预张拉光栅的应变传递率,且两者均在95%以上,与理论分析相符。这说明对测拉应变的实验,预张拉能提高应变传递率;而对测压应变的实验,预张拉会降低应变传递率。

In view of measuring strain on the structure surface by the bare fiber Bragg grating（FBG）, and based on the strain transfer model of fiber layer-cement layer-matrix layer, the prestressing effect on the strain transfer rate is studied theoretically and experimentally. The strain on both positive and negative sides of the equal strength beam is measured by means of the prestressing FBG as well as the normal FBG. In order to eliminate the effect of the length and thickness of the cement, the LOCTITE dispenser is used to control the amount of cement. The curve of strain changing with load is obtained. And through comparing with the theoretical strain value of equal strength beam, the curve of strain transfer rate changing with load is received. The results show that the rate of the prestressing FBG is higher than that of the normal FBG for tensile strain mearsuremnet, both of which are above 96%, while the rate of the prestressing FBG is lower than that of the normal FBG for compressive strain mearsuremnet, both of which are above 95%. It corresponds with the theoretical analysis. It proves that the strain transfer rate is improved thanks to the prestressing in the experiment of tensile strain. On the contrary, the rate is reduced because of the prestressing in the experiment of compressive strain.