GOALI: Distributed Active Acoustic Sensing using a Single Optical Fiber for Interfacial Structural Health Monitoring of Reinforced Concrete Structures

该学术与工业联络资助机会（GOALI）项目研究了有效的传感方法，以评估钢筋混凝土（RC）结构中钢筋和混凝土之间界面的完整性。该方法包括采用基于光纤传感的主动声探测技术。两种模式的结合将允许检测多个位置，这将显著提高检测缺陷和结构退化的能力。研究结果对结构健康监测和许多结构构件的无损检测具有指导意义。一个典型的例子是混凝土结构中早期钢筋腐蚀的检测。NACE（全国腐蚀工程师协会）估计，美国混凝土结构腐蚀损伤修复的成本每年约为1250亿美元。钢筋锈蚀是钢筋混凝土结构劣化和未成熟破坏的主要原因。检测早期钢筋腐蚀的传感能力可以大大降低重建/维修成本，日常维护工作以及施工中不必要的社会成本（例如交通关闭）。更重要的是，可以防止不可预测的结构故障，特别是对于标志性建筑和桥梁。本研究不仅将改变目前钢筋混凝土结构中钢筋腐蚀监测的做法，而且将应用于预应力混凝土结构、钢管道、核电站等关键民用基础设施系统的腐蚀监测。教育努力将激励K-12和本科生进行研究，特别是那些来自代表性不足群体的学生。具体研究目标是利用分布式主动声传感技术研究钢筋混凝土结构中钢筋与混凝土界面处的传感机理。这将通过i)研究圆形几何中的主动单点探测/传感问题来实现；ii)制造分布式有源声光纤传感器。该传感器将附着在混凝土内部燃烧的钢筋表面，能够探测到钢筋内部，并评估钢与混凝土界面的结构健康状况。

This Grant Opportunity for Academic Liaison with Industry (GOALI) project investigates effective sensing methodologies to assess the integrity of the interface between steel bars and concrete in reinforce concrete (RC) structures. The approach consists in the application of active acoustic interrogation with optical fibers-based sensing. The combination of the two modalities will allow sensing a multiple locations, which will significantly improve the ability to detect defects and structural degradations. The results of the research will benefit structural health monitoring and nondestructive testing of many structures components. One representative example is the detection of early-stage steel rebar corrosion in concrete structures. NACE (National Association of Corrosion Engineers) estimates the cost of corrosion damage repair in concrete structures in the USA is approximately $125 billion per year. Corrosion of steel rebars in RC structures is primarily responsible for the deterioration and immature failure of RC structures. Sensing capability to detect early-stage rebar corrosion can greatly reduce the cost for rebuild/repair, routine maintenance efforts, and the unnecessary social costs (e.g., traffic closure) in construction. More importantly, unpredictable structural failures can be prevented, especially for signature buildings and bridges. This research will not only change the current practice for monitoring steel rebar corrosion in RC structures, but also wil be applied to the corrosion monitoring of prestressed concrete structures, steel pipelines, nuclear power plants, and other critical civil infrastructure systems using steel. Educational efforts will motivate K-12 and undergraduate students for research, especially those from the underrepresented groups.The specific research goal is to study the sensing mechanism at the interface between steel reinforcing bars (rebars) and concrete in reinforced concrete (RC) structures using distributed active acoustic sensing. This will be achieved by i) investigating the active single-point probing/ sensing problem in a circular geometry; and ii) creating a distributed active acoustic optical fiber sensor. The sensor will be attached to the surface of steel rebars burned inside concrete, capable of probing into the steel rebars and assessing structural health of the interface between steel and concrete.