The Hernando de Soto Bridge spanning the width of the Mississippi River near Memphis has flipped the script on Simon & Garfunkel’s legendary song and album, Bridge over Troubled Water. A recent inspection of the bridge revealed a significant fracture on the underside of a beam. A more appropriate song for this bridge would be Troubled Bridge over Water.
An inspector with the Arkansas Department of Transportation apparently overlooked the crack in a 2019 review of the bridge’s structural integrity. The Memphis Blues aren’t over for the inspector yet, as criminal charges could be filed. Let’s take a look at what happened with this important bridge along I-55.
Bridge Background
The de Soto Bridge opened in 1973. This structure is a through-arch bridge with double arched trusses. Because of this design, the cables in a few particular spots that are suspending the steel deck have more stress on them than other cables. The crack in the beam was discovered near one of these shortened cables.
It appears as if the crack is a fatigue fracture, which occurs after numerous stress cycles are implemented on the beam. The inspection conducted in May 2021 showed a surprisingly mature fracture. Eventually, it came out that the crack was missed during inspections in both 2019 and 2020. Drone footage from nearly two years ago shows the relatively immature crack.
What Happens Now?
The immediate effects are that roadway travel across this major artery is temporarily halted. It could be several more weeks before even a temporary fix can be implemented so automobile traffic can resume flowing. Hundreds of barges were forbidden from crossing under the bridge for several hours on May 11.
Phase 1 of the repair will involve 18,000 lbs. Of steel to reinforce the fractured beam. The steel plates will attach to both sides of the beam, which will redistribute forces elsewhere on the structure. While the steel splice will take care of the critical need, it could make other components of the bridge vulnerable to similar structural failures.
The design of Phase 2 is still being drawn up. The purpose of this latter phase is to permanently fix the Hernando de Soto Bridge. In the meantime, one can only hope that inspection protocols are more rigidly followed in the future.
Conclusion
It’s a safe bet that the current deficiency within the I-55 bridge connecting Tennessee and Arkansas would have been a simpler and less expensive fix if it had been identified earlier. A variety of architects and structural engineers will be involved in the ongoing temporary and permanent fixes.
DDA Engineers, P.A. has helped Miami-area construction professionals for more than 50 years. Our team provides professional and expert consultative engineering services. If you have a structural engineering need, give us a call at (305) 666-0711 to see how we can partner with you.
DDA Engineers, P.A.
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