## 5 Conclusions  
We proposed a numerical simulation for supporting long-term inspection plans using a passive IRT method for the detection of subsurface damages in concrete bridge decks. The model was developed using FEM, which showed promising agreement with the surface temperatures and thermal gradients measured in the experimental tests, supporting the extrapolation to long-term analysis to find favorable windows for inspections. The results verified that IRT inspections performed during warmer months (spring and summer) enable more reliable identification of the subsurface damage in the concrete structure compared to colder months (autumn and winter) in the case of the study.  
The presented research contributes to the field of thermographic inspection of subsurface defects in reinforced concrete bridge slabs in two different ways. First, the computational simulation can support the practical planning of passive IRT inspections in concrete elements for a long period, considering different locations and weather conditions. Second, the use of the developed model can save the time, effort, and resources spent in the construction of the samples and the visits to the structures to find the best times to perform the measurements.  
The number of factors that influence passive IRT inspections can limit this approach and can lead to discrepancies in the surface temperatures obtained in the simulations and onsite measurements. In addition, the research was developed based on a static damage area in this case study, and the specific prediction results are linked to the configuration of the analyzed damage. However, if a user decides to use the model to test the detection of another type or size of defects, the damage configuration can be changed in the geometry of the model prior to the analysis, and the results will be generated according to the new damage configuration. This procedure can also be followed when the user experiences other material (concrete) parameters, geographical localization, or environmental conditions. Further research efforts could use the finite element model updating technique to improve the accuracy of the results and explore the use of long-lasting inspections in real concrete structures using passive thermography to enable advanced image processing techniques. Studies regarding the possible improvement of characteristics of concrete material to face thermal concrete strains using FEM is also a research opportunity in this field, together with the analysis of the steel reinforcement effect in the heat flow through reinforced concrete structures.  
Conceptualization, S.P., F.D.R. and Z.M.C.P.; methodology, S.P.; validation, S.P., F.D.R. and Z.M.C.P.; investigation, S.P.; writing--original draft preparation, S.P.; writing--review and editing, F.D.R., Z.M.C.P., E.R.A. and X.M.; supervision, F.D.R.; funding acquisition, F.D.R. All authors have read and agreed to the published version of the manuscript.  
This research was partly funded by the National Council for Scientific and Technological Development -CNPq grant number 427757/2016-9.  
Not applicable.  
The data that support the findings of this study are available from the corresponding author upon reasonable request.  
The authors are grateful for the financial support from Fundacao Universidade de Passo Fundo (FUPF).  
The authors declare no conflict of interest.