Strain transfer behavior of notch embedded Fiber Bragg Gratings

The vehicle loads seen on Wyoming roadways are continuously increasing due to the demanding transportation needs of Wyoming's expanding energy industry. The resulting overload conditions experienced by Wyoming's aging bridges have called for the implementation of a structural health monitoring (SHM) system. A SHM system utilizing fiber optic strain sensors called Fiber Bragg Gratings (FBGs) have proven in recent years to be an innovative and effective solution for monitoring bridge conditions. Such a system will allow WYDOT engineers to monitor the damages and fatigue effects of overloaded Wyoming bridges over years of service. This research examined a new method of attaching FBG strain sensors to concrete structural members via adhesive embedment in concrete notches. The proposed method is ideal because it provides ample fiber protection from weathering and vandalism. Additionally, the FBG becomes a rooted component of the structure that is unlikely to detach or be scraped off throughout years of service.;Both a finite element analysis (FEA) and an experimental investigation were conducted to analyze the effectiveness and feasibility of the proposed concrete strain monitoring method. The strain loss over the adhesive layer between the concrete and the FBG sensor was the primary variable of interest in the study. The strain loss directly affects the accuracy of the sensors in measuring the strain of the concrete. Several attachment configurations with different parameters were tested.;The results of this study support the conclusion that there are certain notch embedment configurations that will provide accurate strain measurement of a concrete structural member. It was found that the FEA predicts slightly higher strain transfer than what occurs in real conditions. A feasible procedure for implementing the proposed sensing method in field conditions was developed during the experimental tests.