Real-time Intelligent Monitoring of Reinforced Concrete Structures

随着人们对民用基础设施系统过早老化问题的日益关注，对物理状态量化策略发展的需求日益增加。广泛使用的钢筋混凝土（RC）结构通常体积大、结构复杂，且处于恶劣的环境中，使用寿命相当长。钢筋混凝土结构退化的主要原因是混凝土内嵌钢筋的腐蚀损伤。额外的腐蚀引起裂缝，导致钢筋脱落。钢筋混凝土结构的这种形式的恶化往往超过其他形式的恶化。尽管存在潜在的损伤，有时甚至是潜在的灾难性损伤，但目前仍缺乏一种高效、有效的结构健康监测系统（SHMS）来提供RC结构内部损伤的定量信息。显然，需要建立一个强有力的监测系统，以便为土木结构提供及时的维修行动和安全保障。本研究的目的是开发一种主动分布式传感系统，用于实时量化和可视化钢筋混凝土结构中嵌入损伤的位置和大小。这项工作不仅仅是一个简单的监测系统；它只是检测损坏的存在，而没有识别其对结构安全的重要性。拟议的工作建立在一项概念验证研究的基础上，在该研究中，PI展示了利用在地球物理勘探中广泛使用的迁移技术识别金属中不同大小和形状的损伤及其位置。在这项工作中，类似于检波器的压电片线性阵列在实验中用作致动器和传感器。在均匀板方面取得了初步成功后，提出的研究旨在量化高度非均匀RC结构的损伤，特别是使用分布式压电致动器/FBG传感器网络的钢筋与混凝土的腐蚀和裂纹引起的脱落。激励信号将从安装在混凝土或钢筋上的压电致动器发出；低成本、可靠的光纤分布式传感器将嵌入混凝土中，为钢筋混凝土提供沿其长度方向的动态应变传感。研究计划包括四个主要任务。即：利用射线理论进行波传播建模和散射，开发一种鲁棒的实时叠前偏移技术；原型钢筋混凝土结构物理模型的实验室测量；腐蚀/脱粘对选择性诊断信号和压电和光纤放置的敏感性的测定发展信号处理技术和成像可视化算法，实现高分辨率损伤位置和大小的明确识别。本研究将确定并解决在RC结构中建立SHMS的基本科学和工程挑战。提出的研究将为未来使用分布式压电致动器/FBG传感器网络进行损伤识别和使用迁移技术进行连续监测奠定基础。预计所提出的工作将显著推进传感器技术、应力波模拟、创新迁移技术、损伤重建和可视化以及应力波测量的实验室方法等领域的科学知识。将通过开设有关课程和举办专业讲习班，将已开发的知识和方法纳入教育。通过让本科生参与实验工作，在实验室测试和分析，研究生的研究工作将与本科课程相结合。通过与历史上的黑人大学北卡罗来纳农工大学（North Carolina a&t University）的现有联系，将努力吸引女性和少数族裔学生参与拟议的研究。此外，通过机械和航空航天工程系现有的工业伙伴计划，工业伙伴将作为研究生论文委员会的成员参与其他相关工作。

Real-time Intelligent Monitoring of Reinforced Concrete Structures, CMS proposal 0301441PI: Yuan, NC State UniversityWith 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.