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

University Of Massachusetts Lowell, Lowell MA

Investigators

Abstract

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.