A Robust Methodology for the Standoff Condition Assessment of FRP-Retrofitted Concrete Systems

纤维增强聚合物（FRP）加固和改造钢筋混凝土构件，如梁、柱、板和桥面已经越来越流行。为了远程评估这些改造系统的原位完整性，需要一种高效的无损检测技术。在本研究中，将开发一种强大的独立无损检测方法，利用聚焦于受损区域的机载声波来检测FRP板/板下方的损伤和缺陷。具有各种缺陷结构的实验室样品将受到近距离和远距离的声学阵列的影响。缺陷产生的动态响应将由激光多普勒振动仪（LDV）收集。提出的方法基于这样的概念，即frp -混凝土体系中的脱粘损伤和混凝土空洞引起的局部振动异常与完整区域引起的振动异常有很大不同，它们是损伤尺寸和力学性能的直接函数。拟议的研究代表了多学科的努力，整合了复合混凝土力学，固体中的波传播，声学和激光技术以及计算机科学的知识。它涉及数值模拟、模式识别、信号处理和成像，并结合复杂的复合材料系统行为。因此，该项目将具有强大的智力组成部分，具有在这些多学科领域推进科学知识的潜力，并对开发用于frp粘合混凝土结构完整性评估的强大非接触技术做出重大贡献。这项研究的结果将通过研究出版物和综合教育材料在互联网上广泛传播。这项研究活动将为参与该项目的学生提供先进的培训和研究机会。

Fiber-reinforced polymer (FRP) strengthening and retrofitting of reinforced concrete elements, such as beams, columns, slabs, and bridge decks have become increasingly popular. To remotely assess in-situ integrity of such retrofitted systems an efficient and effective nondestructive testing technique (NDT) is needed. In this research a robust standalone NDT approach utilizing an airborne acoustic wave focused on the damaged area will be developed to detect the damage and flaws underneath the FRP plates/sheets. Laboratory specimens with various defect configurations will be subjected to acoustic arrays from close as well as long distances. Dynamic responses produced by the defects will be collected by laser Doppler vibrometry (LDV). The proposed method is based on the concept that debonding damages and concrete voids in the FRP-concrete system cause local vibration anomalies that are considerably different from those caused by intact regions and that they are direct functions of the damage dimensions and mechanical properties.The proposed research represents a multi-disciplinary effort integrating knowledge from mechanics of composite concrete, wave propagation in solids, acoustic and laser technologies, and computer science. It involves numerical simulation, pattern recognition, signal processing and imaging in conjunction with complex composite material system behavior. Thus, the project will have a strong intellectual component with potential to advance scientific knowledge in these multi-disciplinary areas, and significant contribution toward the development of a robust non-contact technique for integrity assessment of FRP-bonded concrete structure. The findings from this research will be extensively disseminated through research publications and integrated educational materials through internet. The research activity will provide advanced training and research opportunity to the students working on this project.