An X-Ray Tomography Investigation of Bond in Reinforced Concrete

摘要在高能x射线ct扫描仪内进行了大量的钢筋混凝土粘结试验。我们的目标是获得一组三维高分辨率的体积图像的粘结区损伤模式的近全尺寸试样加载。这些图像将允许，在前所未有的程度上，观察和量化的临界内部变形和破坏的结合区的启动和发展。它们还将允许验证高保真数值模型，最终支持从肋级模型到杆级模型的可靠升级。钢筋混凝土中的粘结性能是一个具有巨大实际意义的问题，因为它通常控制构件的行为，并暗示着整个结构的行为。然而，在目前的技术水平，键合区损伤的启动和演变的细节，知之甚少。其结果是，当地的数据需要了解的债券机制的细节，必要的发展可靠的数值模型，迄今为止还没有。X射线层析成像，由于其密集，非侵入性，和非破坏性的性质，有可能满足当地的数据和革命性的债券行为的知识状态的需要。所提出的测试的新奇和困难来自于以下事实：（1）规模大，也就是高能量（线性加速器）x射线源是穿透样本并获得高分辨率3d-ct重建所必需的;以及（2）成像必须在显著的负载下执行，因此完整的测试框架（具有致动器、固定装置等）必须放在扫描仪里除了为困扰工程师数十年的邦德问题提供答案外，该项目还将对教育产生深远的影响。数据集的3d-ct存档以及测试的高质量体绘制图将被打包成网络可用模块并在全国范围内分发。它们将使新一代的学生能够看到他们研究的RC系统的内部实际上是如何出现的，以及它们的内部微观结构如何由于开裂而演变，并在负载下破碎。所产生的媒体丰富的数据目录也将提供机会，向k-12学生展示现代技术在解决民用材料设计问题中的应用。

AbstractA number of reinforced concrete bond experiments will be conducted inside a high-energy x-ray ct scanner. The goal is to obtain a set of three-dimensional high-resolution volumetric images of bond-zone damage patterns for near full-scale specimens under loading. These images will permit, to an unprecedented degree, the observation and quantification of the initiation and progression of critical internal deformation and damage in the bond-zone. They will also allow the validation of high-fidelity numerical models that will ultimately support the reliable upscaling from rib-level models to bar-level models.Bond behavior in reinforced concrete is a problem of enormous practical importance because it often controls the behavior of members and, by implication, behavior of the whole structure. Yet, the details of bond-zone damage initiation and evolution are, in the current state of the art, poorly understood. The result is that the local data required for understanding the details of the bond mechanism, and necessary for developing reliable numerical models, have not been available to date. x-ray tomography, because of its dense, non-invasive, and non-destructive nature, has the potential to fulfill the need for local data and to revolutionize the state of knowledge of bond behavior.The novelty and difficulty of the proposed tests come from the fact that: (1) they are large scale, and hence high-energy (linear-accelerator) x-ray sources are necessary to penetrate the specimens and obtain high-resolution 3d-ct reconstructions; and (2) the imaging has to be performed under significant loading, and hence a complete testing frame (with actuators, fixtures, etc.) has to be placed inside the scanner. In addition to providing answers to questions about bond that have plagued engineers for decades, the project will have a far-reaching impact on education. The 3d-ct archive of data sets together with high-quality volumetric renderings of the tests will be packaged in web-available modules and distributed nationally. They will enable a new generation of students to see how the interior of the RC systems that they study actually appear and how their internal microstructure evolves due cracking, and crushing under loading. The media-rich catalog of data produced will also provide the opportunity to demonstrate to k-12 students the application of modern technology to solving civil material design problems.