Displacement monitoring using distributed macro-strain measurement

As a key parameter the displacement is often monitored to assess the structural performance. However, it is not easy to implement the long-term monitoring under traffic loads especially. A new method is proposed to monitor displacement of flexural structures, based on the distributed macro-strain sensing technique. Within this method the distributed macro-strain was first obtained using long-gauge fiber Bragg grating (FBG) sensors. Then the classical displacement analysis theory, namely force method from the principle of virtual work, was applied to calculate the displacemnet. Finally a cantilever beam installed with the proposed long-gauge FBG sensors was subjected to free vibration to implement the verification. The results have verified the high accuracy of displacement measurement with the proposed method as well as high robustness to noise. Considering the other advantages of distributed optical fiber sensing, the proposed method presents broad application propects especially in long-term structural health monitoring (SHM).