Description
Infrared thermography (IRT) is a non-destructive technique (NDT) known for fast, contactless, and wide area monitoring of concrete structures like bridges in transportation networks. Dealing with practical challenges of IRT such as the determination of favourable timeframe for data collection, detection of defects of various types and geometry, differentiation of the true concrete defects from environmental and operational effects, and so on by laboratory experiments is time-consuming, arduous, and costly. Finite element analysis (FEA) is an indispensable tool for addressing the practical challenges facing the implementation of IRT for structural health monitoring of concrete structures. This paper presents the analysis of finite element models (FEM) of concrete slabs with subsurface defects in the LUSAS software. Initially, the models are validated based on surface temperatures of concrete slabs measured in the laboratory by IR camera. Then, they are used to estimate the variation of thermal contrast, time rate of thermal contrast, and distribution of temperature on the surface with depth of defect. In addition, the results and trends are compared with the experimental measurements. The validated FEMs are used to estimate the amount of energy required for the creation of minimum safe detectable thermal contrast recommended by ASTM D4788-03 standard and other criteria. Finally, after discussion of results, the conclusions, and recommendations for improved implementation of IRT based on FEA, especially for the detection of defects at rebar depth, are outlined.
