Based on observing photos showing the abutments on the east end of the collapsed span, Professor Tom Bible noted that a track hoe loaded with removed beams was sitting on the eastern edge of the span, adjacent to where the eastern beam had been removed.

“The photo indicates that the track hoe was carrying five beams from the 90-foot span,” Bible says. “What was the design load for the bridge span, and particularly what was the wheel load for that design? The track hoe had the effect of concentrating all of the load into one point rather than spreading it out over a series of axles.”

He noted that the photos that show the connections at the west end of the collapsed eastern span show a “precise straight break. This indicates that either there was an expansion joint at this point or that the two spans had been cut apart in anticipation of the demolition. If the two spans had been cut, the lack of continuity would force each span to operate as a simply supported span rather than as two continuous spans.”

Among several conjectures, Bible says: “I would search for evidence to corroborate the conjecture that the load was excessive and that removing adjacent spans caused the structure to behave in ways that were not anticipated or designed for.”