SGER: Ultrasonic Imaging for Concrete Structural Elements

描述嵌入缺陷的位置、大小和形状的视觉图像提供了有关结构状况的直接信息。然而，构建有效的图像需要许多单独的数据，并且混凝土结构固有的大尺寸导致构建足够的图像需要巨大的数据量。一种增强超声成像应用的方法是消除传感器和被测结构之间物理接触的需要。PI最近完成了混凝土空气耦合超声检测的研究。研究结果表明，通过空气耦合传感器的完全无接触配置可以检测穿过混凝土的超声波。本课题将探讨空气耦合超声层析成像的有效性。这些方法将首先使用缩小尺寸（五倍尺寸）的混凝土柱样品进行实验评估。对于每个扫描配置，将考虑矩形和圆形横截面柱样本。一些混凝土样品将含有嵌入的人工体积（空洞）和平面（裂缝）缺陷。其他无缺陷的试件将使用伊利诺伊大学的五级测试设备进行模拟地震荷载。然后将其应用于全尺寸混凝土柱，目前正在伊利诺伊大学NEES小组项目的一部分进行测试；作为NEES项目的一部分，在施加机械（地震）载荷之前和之后，将对这些柱进行无损成像。这项工作的成功完成将使混凝土结构的内部缺陷表征成为可能。与此同时，这项工作为PI目前正在开发的一项新兴技术的发展提供了一个独特的机会：混凝土结构的空气耦合传感。

Visual images that describe the location, size and shape of embedded defects provide directinformation about the condition of a structure. Many individual data are needed to construct aneffective image however, and the inherent large size of concrete structures results in an enormousamount of data needed to construct an adequate image. One approach to empower the applicationof ultrasound for such imaging is to eliminate the need for physical contact between the sensorand tested structure. The PI has recently completed research on air-coupled ultrasonic testing forconcrete. The research findings illustrate that ultrasonic waves traveling through concrete can bedetected with a fully contact-free configuration using air-coupled sensors. In this project, theefficacy of air-coupled ultrasonic tomographic imaging will be investigated. The methods will first beevaluated experimentally using reduced-scale (fifth-scale) concrete column samples. Bothrectangular and circular cross-sectioned column samples will be considered for each scanconfiguration. Some concrete samples will contain embedded artificial volumetric (void) andplanar (crack) defects. Other defect-free specimens will be subjected to simulated seismic loads,using the fifth-scale test facility at the University of Illinois. Application to full-scale concretecolumns, which are currently being tested as part of a NEES small group project at the Universityof Illinois, will then follow; the columns will be non-destructively imaged before and after themechanical (seismic) loading is applied as part of the NEES project. Successful completion of the work will enable unparalleled internaldefect characterization for concrete structures. At the same time, the effort provides a uniqueopportunity to extend development of an emerging technology that is currently being developedby the PI: air-coupled sensing for concrete structures.