The goal of the condition assessment of concrete structures is to gain an insight into current condition of concrete and the existence of defects, which decrease durability and usability of the structure. Defects are quite difficult to detect using infrared thermography when concrete elements cannot be thermally excited with the Sun, together with unfavorable thermophysical properties of concrete structures. In this paper, principal component thermography (PCT) is applied as a post-processing method to a sequence of thermograms in order to enhance defect detectability in concrete structures. Defects are detected by analyzing a set of empirical orthogonal functions (EOFs), which were acquired by applying principal component analysis to a sequence of thermograms. The research was performed using concrete samples containing known defects, which were tested using a step heating thermography setup. The results of presented research show that PCT is an effective post-processing method to improve defect detection in concrete structures. By effectively improving the defect detection, PCT has a potential to improve the non-destructive testing (NDT) accuracy of using infrared thermography (IRT) on concrete structures, especially in shaded areas of such structures. The research also shows the defect detectability depending on concrete type thermal excitation setup and defect geometry.

中文翻译：

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用于混凝土缺陷检测的主成分热成像。

混凝土结构状态评估的目的是深入了解混凝土的现状和缺陷的存在，这些缺陷会降低结构的耐用性和可用性。当混凝土元素不能被太阳热激发时，使用红外热成像技术很难检测到缺陷，同时混凝土结构的热物理性能也很差。在本文中，将主成分热成像（PCT）作为热分析图序列的后处理方法，以增强混凝土结构中的缺陷检测能力。通过分析一组经验正交函数（EOF）可以检测出缺陷，这些经验正交函数是通过对热像图序列进行主成分分析而获得的。该研究是使用含有已知缺陷的混凝土样品进行的，使用步进加热热成像设置进行了测试。已有研究结果表明，PCT是改善混凝土结构缺陷检测的有效后处理方法。通过有效地改善缺陷检测，PCT有潜力提高在混凝土结构上，尤其是在此类结构的阴影区域中使用红外热成像（IRT）的无损检测（NDT）准确性。研究还表明，取决于混凝土类型的热激励设置和缺陷几何形状，缺陷的可检测性。PCT有可能提高对混凝土结构（尤其是在此类结构的阴影区域）使用红外热成像（IRT）的无损检测（NDT）准确性的潜力。研究还表明，取决于混凝土类型的热激励设置和缺陷几何形状，缺陷的可检测性。PCT有可能提高对混凝土结构（尤其是在此类结构的阴影区域）使用红外热成像（IRT）的无损检测（NDT）准确性的潜力。研究还表明，缺陷检测能力取决于混凝土类型的热激励设置和缺陷几何形状。