Real-time Intelligent Monitoring of Reinforced Concrete Structures, CMS proposal 0301441
PI: Yuan, NC State University
With a growing concern on the premature deterioration of civil infrastructure systems, the demand for the development of strategies in quantifying physical condition is ever increasing. The widely used steel-reinforced concrete (RC) structures are normally massive and complex and are subjected to harsh environment for a rather long service life. The leading cause of degradation of RC structures is corrosion damage to the rebar embedded in the concrete. Additional corrosion induces cracks leading to debonding of the rebar. This form of deterioration in RC structures often outweighs other forms of deterioration. Despite the potential damages, and sometimes potentially catastrophic ones, an efficient and effective structural health monitoring system (SHMS) that provides quantitative information of damage inside RC structures is still lacking. It is clear that a robust monitoring system needs to be developed to provide timely maintenance action and safety for civil structures. The objective of this research is to develop an active distributed sensing system for quantifying and visualizing location and sizing of embedded damage in RC structures in real time. The work goes beyond a simple monitoring system; it merely detects the presence of damage without identifying its importance on the safety of the structure. The proposed work builds on a proof-of-concept study in which the PI demonstrated the identification of different sizes and shapes of damages and their locations in metals utilizing migration technique, which is widely used in geophysical exploration. In that work, a linear array of piezoelectric patches analogous to the geophones was used in the experiments as actuators and sensors. With this preliminary success in homogeneous plates, the proposed research aims at quantifying the damage in highly inhomogeneous RC structures, in particular the corrosion and crack-induced debonding of the rebars from the concrete using a distributed piezo actuator/FBG sensor network. Excitation signals will be emitted from piezo actuators, either mounted on the concrete or on the rebars; low-cost and reliable optical fiber distributed sensors will be embedded in the concrete to provide dynamic strain sensing along their lengths for reinforced concrete.
The research plan consists of four major tasks. Namely: Development of a robust and real-time prestack migration technique using ray theory for wave propagation modeling and scattering; Laboratory measurements of physical models of prototype RC structures; Determination of sensitivity of corrosion/debonding to selective diagnostic signals and to piezo and optical fiber placement; Development of signal processing techniques and imaging visualization algorithms for unambiguous identification in location and sizing of the damages with high resolution. This study will identify and address basic scientific and engineering challenges toward establishing SHMS in RC structures. The proposed research will lay the groundwork for the future use of a distributed piezo actuator/FBG sensor network for damage identification and continuous monitoring using migration technique. It is envisioned that the proposed work will significantly advance scientific knowledge in the areas of sensor technology, stress wave simulation, innovative migration technique, damage reconstruction and visualization, and laboratory methodologies with stress wave measurements. Developed knowledge and methodologies will be integrated into education via development of relevant courses and professional workshops.
Through involvement of undergraduate students in the experimental work in the laboratory testing and analysis, the graduate research work will be integrated with undergraduate program. Through existing ties with North Carolina A&T University, a historically black university, effort will be made to attract female and minority students in performing the proposed research. Moreover, through an existing Industrial Partnership Program in the Department of Mechanical and Aerospace Engineering, industrial partners will be involved as members of the graduate thesis committee in other relevant work.
