I'm not an engineer, but I hadn't seen much like it either. When I first saw photos of the collapsed bridge along with the renderings of that it would look like when completed, I concluded that the architects/engineers had attempted to make a concrete beam with the wrong proportions... this based on what I have read of Victorian cast iron beam designs and modes of failure.
Maybe the schools stopped teaching about empirical dead white guy engineering and the school of hard knocks vis-a-vis brittle materials and tension/compression (Dee Bridge, etc).
Concrete works great with compression loads. It fails easily under tension. The design most likely incorporated cables in the bottom of the beam/bridge that could be tightened to place the bottom of the beam/bridge in compression. I suspect the cables were tightened after the concrete cured and reached a specific strength. The tightening was calculated to allow the beam/bridge to be moved onto the piers. Then additional tensioning was applied to enable the bride to support additional loads other than the dead weight. During that process something got out of sync and the load exceeded what the concrete could withstand.