This isn't Paul Doumer, this is a relatively weak structure with critical load points asking for a TB2 strike or 2.
It is a weak structure as the bridge deck spans are retained by gravity, not hard structure. The steel bridge spans must have a mounting system to allow for thermal expansion and contraction which, with the hot summers and cold winters of the area, is substantial. For example, a 200 foot steel beam will expand about 2 inches with a temperature delta of 120° F (sorry about the imperial units). There are multiple bridge support systems to accomplish this, though from the photos I suspect the rocker and pin bearing system is used; as one can see, the span is held in place only by its own weight.
This seems susceptible to earthquake or explosive damage; it's not surprising the spans fell. Joints would seem a good target for rocket attack.....
Edited for gramma.