Looked like an awful lot of concrete for a pedestrian bridge, too. Pretty thick. Come to think of it, decking with non-tensioned rebar might have been best for forms, and a thinner slab.
Also, come to think of it, there was no good reason for that heavy slab on top. That should have been some kind of truss bridge sheeted with lighter materials.
Concrete (especially thin, long, pre-cast/post-tensioned concrete like this deck) is a poor choice for the complex stresses (tension, compression, and moment-resisting at each corner) in a beam truss like this one.
The upper concrete was apparently intended as a sunshade, it has many fewer Post-tensions bars/cables in it than the lower beam.
Apparently cracks were found in the bridge the first days after it was lifted in place, there were people on top trying to adjust/re-tension the cables when it collapsed. But the cars underneath were permitted to drive under anyway - the main intention of the design was “appearance” (the white reflective concrete was a main selling point of the proposal) and “style” and (Obama’s favorite) “ecological minimized impact” - which is why concrete was chosen over “unimaginative” “plain steel” .
Yes there was. Any self-respecting team of feminist engineers wouldn't be caught dead designing anything with a glass ceiling.