Serious question - do you really think the team of engineers who designed these bridges aren't aware of the existence of solar radiation or climate on planet earth?
Counter question - do you think the team of engineers would scrap their whole, hard-earned design because e.g. they found out that after 20 years it would stain to an ugly yellowish hue in sunlight?
Oooh, they are aware. Keep in mind that Boeing's also was aware about possible issues with the MCAS in the 737 MAX and it went flying (and crashing) anyway.
The list of things that have failed due to "solar radiation or climate" includes many structures designed by engineers.