An X-Ray Tomography Investigation of Bond in Reinforced Concrete

将在高能x射线ct扫描仪内进行钢筋混凝土粘结实验。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在加载下。这些图像将允许在前所未有的程度上观察和量化粘结区临界内部变形和损伤的开始和进展。它们还将允许验证高保真的数值模型，这些模型最终将支持从肋级模型到棒级模型的可靠升级。钢筋混凝土的粘结性能是一个具有重大实际意义的问题，因为它往往控制着构件的性能，进而影响着整个结构的性能。然而，在目前的技术水平下，对粘结带损伤发生和演化的细节了解甚少。结果是，了解键合机制细节所需的局部数据，以及开发可靠的数值模型所必需的数据，到目前为止还无法获得。x射线断层扫描由于其致密、非侵入性和非破坏性的特性，有可能满足对局部数据的需求，并彻底改变键行为的知识状态。所提出的测试的新颖性和难度来自于以下事实：(1)它们是大规模的，因此需要高能（线性加速器）x射线源来穿透样品并获得高分辨率的3d-ct重建；(2)成像必须在很大的载荷下进行，因此必须在扫描仪内放置一个完整的测试框架（带有执行器、夹具等）。除了解答困扰工程师们几十年的有关纽带的问题外，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效果图将打包在网络可用模块中，并在全国分发。他们将使新一代的学生看到他们所研究的RC系统的内部是如何出现的，以及它们的内部微观结构是如何在加载下由于开裂和破碎而演变的。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土木材料设计问题方面的应用。

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.