The bridge railing collapse in Chattanooga on the morning of April 1 was likely caused by an illegally oversized load, according to the Tennessee Department of Transportation (TDOT).
Last summer, in its bi-annual routine inspection, the Interstate 75 bridge was given an overall rating of “fair,” scoring no lower than six on a zero-to-nine point scale in any category. With the structure passing muster just months ago, officials announced within hours of the collapse that it was likely caused by a collision.
According to TDOT Chief Engineer Paul Degges, five steel reinforcement cables broke in the same place, causing the railing to crumble onto the I-75/I-24 exchange below. According to TDOT engineers, the impact that severed the cables was like from an oversized load striking the bridge, presumably something steel like a crane or other equipment.
“Looking at how the elements failed on [the bridge] and how the pieces fell on the road, we’ve come to the initial conclusion that some type of over-dimensional load hit the bottom of the bridge,” Degges said, adding that it “seems improbable” that they all failed at the same time, in the same place, without some sort of collision or any signs of abnormal wear.
The collapse did not cause any injuries itself, but a motorist hit the fallen debris, sustaining non-life-threatening injuries, according to TDOT.
All lanes at the interchange of I-75 and I-24 closed for several hours, stopping traffic in all directions throughout most of the day.
Though Degges said the cables “[look] like someone took scissors through [them],” there is no available footage of the bridge or witnesses to confirm the collision theory.
While an inventory of American bridges released by the American Road & Transportation Builders Association (ATRBA) on April 1 lists Tennessee as the eighth-best state for bridge quality, TDOT says about 50 such collisions occur with bridges in the state each year.
ARTBA’s analysis also revealed that the pace of bridge repair is the slowest since it began compiling the report five years ago.
“At the current pace, it would take more than 80 years to replace or repair the nation’s structurally deficient bridges,” said ARTBA chief economist Alison Premo Black. “America’s bridge network is outdated, underfunded and in urgent need of modernization. State and local governments just haven’t been given the necessary resources to get the job done.”