Optical fiber based integrity test of civil engineering materials: Numerical analysis

“Major advancement in Civil Engineering cannot be accomplished without the help of sensors. Among different types of sensors, fiber-optic sensor is known for its light weight, high accuracy, resolution, immunity to electromagnetic interference, and resistance to harsh environment. This research mainly focuses on fiber-optic sensor application on concrete structures as temperature sensor. Thermal Integrity Profiling (TIP) is a non-destructive integrity testing method which makes use of the hydration heat from the concrete curing process to detect defects within a drilled shaft. Any defect of concrete could result in a temperature anomaly in a drilled shaft. The accuracy of the current method to measure temperature distribution within the concrete shaft is limited by the interval between sensors. To improve it, we implement fiber-optic sensor with high spatial resolution as thermal sensor. The flexibility of fiber-optic sensor allows it to be wrapped spirally around the reinforcement cage. Both changes to the method provide a more comprehensive temperature distribution data. Current method to interpret the data is so-called effective radius method. This method could underestimate the size of defect, especially an inclusion defect. We propose a new method to estimate the location and size of defect based on the high-resolution temperature distribution data measured by fiber-optic sensor. Moreover, we also take into account of the effect of aggregate in this study. Concrete is not a homogeneous material by containing aggregates with different size, shape and distribution. In this study, we investigate how the existence of coarse aggregate may affect the result. Countermeasure to minimize the effect of aggregate on thermal data interpretation is also proposed in this research”--Abstract, page iv