Structural monitoring of the FRP-concrete hybrid tube using FBG sensors

초록

This study is to investigate the static and dynamic behavior of the FRP-concrete hybrid tube using the multiplexed fiber Bragg grating (FBG) sensor arrays. The FRP tube with an outside diameter of 420 mm and a wall thickness of 30 mm was fabricated. The steel cage system was then inserted inside the FRP tube and concrete was filled. The length of the FRP-concrete hybrid tube specimen was 4.0 m. Wavelength division multiplexing (WDM)-based FBG sensors were attached the top and bottom surface of the test specimen. The physical quantities such as stains, curvatures, and vertical deflections are measured from the laboratory test. The strains are directly measured from multiplexed FBG sensors at various locations of the hybrid tube followed by curvature calculations based on the plane section assumption. Vertical deflections are then estimated using the Bernoulli beam theory and regression analysis. The experimental program involved two phases. First, the dynamic characteristics of the hybrid strut were identified using a modal test. An FBG-based accelerometer was also installed on the surface of the structure. The second phase involved the measurement of the nonlinear static behavior until failure to examine the applicability of the FBG strain sensors under severe load states and to investigate the failure mechanism of the FRP-concrete hybrid tube. The measured values from the FBG-based sensors are compared with the results using electric signal-based sensors. The results show that the FBG sensing system is promising and can improve the efficiency of local and global monitoring for the FRP-concrete hybrid system.