I have a question about thermography on bridges. I have a bridge with circular internal cavities. Now, I am examining the underside of the bridge using thermography, and the areas of the cavities appear cooler. I understand that concrete above the cavities cools or heats up more quickly, and that the cavities slow down the heat flow from top to bottom. However, I am unsure how the contrasts of the cavities change throughout the day. What happens when the bridge heats up? How would the contrasts change from morning to afternoon to evening? what happens when sun is directlxý shining on the bridge?
Maybe someone can help me.