Abstract
In bridge structures, concrete decks have a higher risk of damage than other components owing to the direct impact of traffic. This study aims to develop a comprehensive system for bridge inspection using passive infrared thermography (IRT). Experiments were conducted on a concrete specimen (assumed as the surface of the bridge deck) embedded artificial delaminations with different width-to-depth ratios (WTDRs). Both professional handheld IR camera (H-IRC) and a UAV mounted with an IR camera (UAV-IRC) were employed simultaneously to capture the surface temperature of the structure. The present work indicates that the passive IRT technique with an H-IRC can be used to detect delaminations located at depths of 4 cm or less from the structure surface if the WTDRs are not lesser than 1.9 for daytime and 2.5 for nighttime when testing on a sunny day. In addition, the larger the WTDR, the higher the temperature difference can be produced, thus delaminations could be observed more clearly. Furthermore, our study suggests that the concrete bridge deck inspection using passive IRT can produce appropriate results if the inspection is performed from 10:00 to 15:00 or from 19:30 to approximately 2:00 on a sunny day. Good agreement between the results obtained from tests using H-IRC and UAV-IRC was observed, which validates the application of UAV-IRC in real structure inspection.
Highlights
In bridge structures, compared to other components, defects occur more frequently in the concrete deck because it is directly subjected to traffic loads [1,2]
If delaminations/spalls occur inside the concrete bridge deck, it means that it does not does not belong to the condition state 1
An effort was made to consider the possibility of simultaneously using the results from the handheld IR camera (H-IRC) and the IR camera hanged on a unmanned aerial vehicles aerial vehicles (UAVs) (UAV-IRC)
Summary
In bridge structures, compared to other components, defects occur more frequently in the concrete deck because it is directly subjected to traffic loads [1,2]. Materials 2019, 12, 3996; doi:10.3390/ma12233996 www.mdpi.com/journal/materials a few hours should be spent to inspect just small regions of structures that are not exposed directly to the sun because the structure surface must be heated by an artificial heat source [15,16,17,18,19,20,21,22,23,24,25,26,27]. In active IRT, several minutes to a few hours should be spent to inspect just small regions of structures that are not exposed directly to the sun because the structure surface must be heated by an artificial heat source [15,16,17,18,19,20,21,22,23,24,25,26,27]. The information related to potential delaminations can be extracted accurately without using extra artificial heatstructure
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