They normally have an Achilles heel though: fire. Heat will usually weaken the composite quickly, unless it's a special epoxy and fiber material heat-cured at high temperature. But then your cost will go way, way up. Maybe they have a solution.
I wonder if the sun will accelerate or pull (dry out) epoxy/base liquid used to hold the mix together . I didn’t see in the article where the girders were weather tested (but they must have)
How often do bridges catch fire?
Composites don’t do well with impact damage, especially if the fibers crack.
That's one. Cost is another.
Cheap, high quality, fast - pick two at most.