Guided Ultrasonic Wave Methodology to Characterize the Performance of FRP Patches in Repaired and Rehabilitated Concrete Components

引导超声波方法表征修复和复原混凝土构件中 FRP 补片的性能

• 批准号: 0201283
• 负责人: Laurence Jacobs
• 金额: $ 15.5万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-15 至 2006-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0201283&HistoricalAwards=false
• 关键词: Guided; Ultrasonic; Wave; Methodology; Characterize

ABSTRACTThe rehabilitation, upgrading and retrofitting of existing reinforced concrete (RC) structures is one of the most difficult challenges facing structural engineering today. One retrofitting method that has gained widespread acceptance over the last decade involves externally bonding fiber reinforced plastic (FRP) patches on to the tension face of a concrete beam or slab, thus increasing the beam's (or slab's) flexural stiffness and loading capacity. The increased usage of these FRP patches in these applications has created the requirement for reliable nondestructive evaluation (NDE) techniques capable of characterizing these bonded patches. Any candidate NDE technique must be capable of providing quantitative and meaningful information (from an engineering design perspective) about the characteristics of an in situ FRP patch. The most critical element from a quality assurance (and thus NDE inspection) point of view is the adhesive bond layer - as opposed to the FRP patch itself. Concrete repair procedures typically use a high quality FRP patch that is manufactured in a controlled environment. This is in contrast to the adhesive bond layer, which is field assembled, often under adverse conditions. There are two important quality assurance/NDE inspection problems for these adhesively bonded FRP patches that can be addressed with guided wave techniques. The first is concerned with the measurement of the material properties of the adhesive layer. Guided waves can be used to determine in situ adhesive bond properties, such as the shear modulus of an epoxy bond. The second inspection problem is the measurement of the adhesion properties, the quality of the bonding at the two interfaces between the adhesive and the adherends. This is a critical issue for bonded FRP patches, especially the adhesion properties of the concrete-to-adhesive interface. The proposed research develops a NDE methodology that uses guided ultrasonic waves to characterize the in situ bond properties of a FRP patch in three tasks: Task 1. Understand the underlying mechanics of the propagation of guided ultrasonic waves in these bonded components. This task examines the behavior of ultrasonic waves in a FRP patch bonded to a concrete component, quantifying the effect of certain bond parameters on the propagation of guided waves in the bonded assembly. This forward problem involves both experimental studies and numerical simulation of FRP patches, concentrating on directly measurable acoustic parameters. Task 2. Interpret the experimental/numerical results from Task 1 in terms of relevant, engineering parameters in order to develop a quantitative relationship between these acoustic measurements and critical FRP patch performance metrics. This task relates these directly measurable, guided wave attributes (such as dispersion curves that provide wave speed/frequency relationships) to material properties that are essential to engineering design. The specific parameters quantified in this research are: the bulk properties of the in situ adhesive layer, including thickness and stiffness; and the adhesion properties of this adhesive layer (particularly the concrete-to-adhesive interface), including detection of any voids, gaps or regions of disbonds. Task 3. Conduct a preliminary study that establishes the effectiveness of an inversion technique for the evaluation of these guided waves. This inverse problem uses neural networks to determine the bulk elastic properties, thickness and adhesion characteristics of an in situ adhesive bond from experimentally measured guided waves. The results of this proof-of-principle study are critical for the development of an efficient, real-time field inspection methodology. This research project operates under the premise that education and research are equally important in developing innovative NDE methodologies for civil infrastructure. In addition to performing basic and applied research, academic institutions have a primary responsibility to train students so that they can meet the requirements of the workplace. With this in mind, an education program is proposed that will educate and train a new generation of engineers to address issues relating to NDE of repaired and rehabilitated RC components.

摘要现有钢筋混凝土结构的修复、升级和改造是当今结构工程面临的最困难的挑战之一。 在过去的十年中，一种得到广泛接受的改造方法涉及将纤维增强塑料（FRP）贴片外部粘结到混凝土梁或板的张力面上，从而增加梁（或板）的抗弯刚度和承载能力。 这些FRP补片在这些应用中的使用增加，产生了对能够表征这些粘合补片的可靠无损评价（NDE）技术的需求。 任何候选无损检测技术必须能够提供定量和有意义的信息（从工程设计的角度来看）的特点，在现场FRP补丁。 从质量保证（以及无损检测）的角度来看，最关键的因素是粘合层-而不是FRP补片本身。 混凝土修补程序通常使用在受控环境中制造的高质量FRP补丁。 这与通常在不利条件下现场组装的粘合剂粘结层形成对比。 对于这些粘接FRP补片，有两个重要的质量保证/NDE检查问题可以用导波技术解决。 第一个是关于粘合剂层的材料特性的测量。 导波可用于确定原位粘合剂粘结性能，例如环氧树脂粘结的剪切模量。 第二个检测问题是测量粘合性能，即粘合剂和被粘物之间两个界面处的粘合质量。 这是一个关键的问题，粘结FRP补片，特别是混凝土粘合剂界面的粘合性能。 拟议的研究开发了一种无损检测方法，使用引导超声波来表征在三个任务中的FRP补丁的原位粘结性能：任务1。 了解这些粘合部件中导波超声波传播的基本机制。 这项任务检查的行为，超声波的FRP贴片粘结到混凝土组件，量化的影响，某些键参数的导波在粘接组件的传播。 这个正问题涉及FRP贴片的实验研究和数值模拟，集中在直接测量的声学参数。 任务2. 根据相关的工程参数解释任务1的实验/数值结果，以便在这些声学测量和关键FRP贴片性能指标之间建立定量关系。该任务将这些可直接测量的导波属性（例如提供波速/频率关系的色散曲线）与工程设计所必需的材料特性相关联。 在这项研究中量化的具体参数是：在原位粘合剂层的散装性能，包括厚度和刚度;和该粘合剂层的粘合性能（特别是混凝土粘合剂界面），包括检测任何空隙，间隙或区域的剥离。 任务3. 进行初步研究，建立反演技术的有效性，这些导波的评价。 这个逆问题使用神经网络来确定体弹性性能，厚度和粘附特性的原位粘合剂结合从实验测量导波。 该原理验证研究的结果对于开发高效、实时的现场检测方法至关重要。 本研究项目的前提下，教育和研究是同样重要的，在开发创新的无损检测方法的民用基础设施。 除了进行基础和应用研究外，学术机构还负有培训学生的主要责任，使他们能够满足工作场所的要求。 考虑到这一点，提出了一个教育计划，将教育和培训新一代的工程师，以解决有关NDE的维修和修复RC组件的问题。