Nondestructive Evaluation of FRP-Confined Concrete Using Microwave

利用微波对FRP约束混凝土进行无损评价，CMS项目0324607PI: Oral Buyukozturk， mith纤维增强塑料（FRP）复合护套系统已经成为钢筋混凝土柱和桥墩传统施工、加固和修复的替代方案。大量的公共和私人项目都在追求这种技术，并且预计会不断升级，特别是在地震活跃地区。然而，一种能够评估FRP护套系统内部混凝土状况的高效、有效的结构评估技术尚未出现。很明显，一种可靠的混凝土成像技术需要尽快发展，以赶上激增的工业应用。本研究的目的是开发和应用有效的无损评估（NDE）成像技术，利用宽带雷达可视化和量化FRP脱层和混凝土开裂和破碎等FRP约束钢筋混凝土构件的损伤。为了实现这一目标，将开发用于自动处理测量数据的理论模型和图像重建算法设计，同时在实验室和现场设置中对物理模型进行实验研究。还将建立各种FRP、混凝土和FRP-混凝土混合介质的电磁（EM）特性数据库，以促进这些发展。研究计划包括四个主要任务：(a)波传播和散射的数值模拟；(b) FRP、混凝土和FRP-混凝土混合介质介电性能的测定；(c)物理雷达测量；(d)信号处理和图像重建。这四项任务在本质上是紧密相连的，并将以迭代和进化的方式进行。对于这项提出的工作，提出了一种使用宽带雷达的新型数据聚焦方法，用于有效检测与FRP粘结和约束钢筋混凝土系统相关的各种损伤机制。由于使用宽带雷达检测frp混凝土损伤的新颖性，自2002年9月以来，一项为期一年的探索性研究已在NSF小额资助探索性研究（SGER）计划下进行，以初步证明本文提出的方法的潜在能力。从目前的勘探工作来看，取得了可喜的成果。根据目前的建议，寻求资金以充分发展方法并进行全面的理论/实验研究，以实现上述目标。考虑到它的非传统土木工程性质，该项目将综合结构工程、材料科学、电气工程和计算机科学领域的知识和理解。这项多学科研究项目将由麻省理工学院土木与环境工程系、电气工程与计算机科学系、电子研究实验室和林肯实验室合作进行。预计拟议的工作将显著推进计算机模拟、创新成像概念、信号处理和图像重建以及处理雷达测量的实验室方法等领域的科学知识。作为制造该领域有效设备的基础，知识的发展将直接影响该行业，并使工程师、交通基础设施社区和全球决策当局受益。所开发的知识和技术的应用将有助于确保公共安全，防止使用FRP复合材料修复或更新的结构系统出现意外故障。已开发的知识和方法将通过课程和专业讲习班融入教育。将尽一切努力鼓励女性和少数民族学生参与拟议研究的进行。

Nondestructive Evaluation of FRP-Confined Concrete Using Microwave, CMS project 0324607PI: Oral Buyukozturk, MITFiber-reinforced plastic (FRP) composite jacketing systems have emerged as an alternative to traditionalconstruction, strengthening, and repair of reinforced concrete columns and bridge piers. A large numberof projects, both public and private, have gone after such technology and escalating deployment has beenexpected, especially in seismically active regions. Yet, an efficient and effective structural evaluationtechnology that is capable of assessing the concrete conditions inside the FRP jacketing systems islacking. It is clear that a reliable concrete imaging technology needs to be soon developed to catch upwith the surging industrial applications.The objective of this research is to develop and apply effective nondestructive evaluation (NDE) imagingtechniques to visualize and quantify damages such as FRP delaminations and concrete cracking andcrumbling in FRP-confined reinforced concrete members using wideband radar. To achieve the objective,theoretical models and design of image reconstruction algorithms will be developed for automaticprocessing of measured data in parallel with experimental studies of physical models both in laboratoryand field settings. A database of electromagnetic (EM) properties of various FRP, concrete, and FRP-concrete hybrid media will also be established to facilitate these developments. The research plan consistsof four major tasks: (a) Numerical modeling of wave propagation and scattering, (b) Determination ofdielectric properties of FRP, concrete, and FRP-concrete hybrid media, (c) Physical radar measurement,and (d) Signal processing and image reconstruction. The four tasks are closely knitted in nature and willbe conducted in an iterative and evolutionary fashion.For this proposed work, a novel data focusing methodology using wideband radar is proposed for aneffective detection of various damage mechanisms associated with the FRP bonded and confinedreinforced concrete systems. Owing to the novelty of using wideband radar to detect damages of FRPconfined concrete, a one-year exploratory study has been underway since September 2002 under the NSF Small Grant Exploratory Research (SGER) program to initially demonstrate the potential capability of the herein proposed methodology. From this exploratory work thus far, promising results have been obtained. With this present proposal, funding is sought to fully develop the methodology and perform acomprehensive theoretical/experimental research toward achieving the objectives as stated above.Considering its non-traditional civil engineering nature, this project will synthesize the knowledge andunderstanding that has been developed in the areas of structural engineering, material science, electricalengineering and computer science. This multidisciplinary research project will be performed withcollaboration of Department of Civil and Environmental Engineering, Department of ElectricalEngineering and Computer Science, Research Laboratory of Electronics, and Lincoln Laboratory of theMassachusetts Institute of Technology.It is envisioned that the proposed work will significantly advance scientific knowledge in the areas of computer simulation, innovative imaging concepts, signal processing and image reconstruction, and laboratory methodologies dealing with radar measurements. Development of knowledge as a basis for manufacturing an effective equipment in this field will directly impact the profession, and benefit engineers, transportation infrastructure communities, and decision-making authorities worldwide. Application of the knowledge and technology developed will help ensure public safety against unanticipated failures of structural systems repaired or renewed using FRP composites. Developed knowledge and methodologies will be integrated into education via course curriculums and professional workshops. Every effort will be made to encourage female and minority student participation in the conduct of the proposed research.