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

纤维增强聚合物(FRP)加固和加固钢筋混凝土构件，如梁、柱、板和桥面已变得越来越普遍。为了远程评估这种改装系统的现场完整性，需要一种高效和有效的无损检测技术(NDT)。在这项研究中，将开发一种稳健的独立无损检测方法，利用机载声波聚焦于损伤区域来检测FRP板/板下的损伤和缺陷。具有各种缺陷配置的实验室样品将从近距离和远距离受到声阵的影响。缺陷产生的动态响应将通过激光多普勒测振仪(LDV)进行采集。该方法基于这样的概念，即FRP-混凝土系统中的脱粘损伤和混凝土空洞引起的局部振动异常与由完整区域引起的局部振动异常有很大的不同，并且它们是损伤尺寸和力学性质的直接函数。所提出的研究是综合了组合混凝土力学、固体中的波传播、声学和激光技术以及计算机科学的多学科知识。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，具有推动这些多学科领域的科学知识的潜力，并为开发用于FRP粘结混凝土结构完整性评估的强大的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互联网上的综合教育材料广泛传播。研究活动将为参与该项目的学生提供高级培训和研究机会。

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.