One of the concerns about the use of passive Infrared Thermography (IRT) for structural health monitoring (SHM) is the determination of a favorable period to conduct the inspections. This paper investigates the use of numerical simulations to find appropriate periods for IRT-based detection of subsurface damages in concrete bridge slabs under passive heating along a 1 year of time span. A model was built using the Finite Element Method (FEM) and calibrated using the results of a set of thermographic field inspections on a concrete slab sample. The results showed that the numerical simulation properly reproduced the experimental thermographic measurements of the concrete structure under passive heating, allowing the analysis to be extended for a longer testing period. The long-term FEM results demonstrated that the months of spring and summer are the most suitable for passive IRT inspections in this study, with around 17% more detections compared to the autumn and winter periods in Brazil. By enhancing the possibility of using FEM beyond the design stage, we demonstrate that this computation tool can provide support to long-term SHM.

中文翻译：

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红外热像仪检测混凝土板表面下分层的长期数值分析

对于使用被动式红外热像仪（IRT）进行结构健康监测（SHM）的关注之一是确定进行检查的有利时机。本文研究了数值模拟的使用，以发现适当的时间段，用于基于IRT的被动加热条件下的混凝土桥梁板沿1年时间跨度的地下损伤检测。使用有限元方法（FEM）构建模型，并使用一组对混凝土板样本进行的热成像现场检查的结果进行校准。结果表明，数值模拟正确地再现了被动加热条件下混凝土结构的实验热成像测量结果，从而使分析可以延长更长的测试时间。长期的有限元分析结果表明，在本研究中，春季和夏季是最适合被动IRT检查的月份，与巴西的秋季和冬季相比，检测次数增加了约17％。通过提高在设计阶段之外使用FEM的可能性，我们证明了该计算工具可以为长期SHM提供支持。