We get a bit blasé about modern large scale engineering.
Then I read a sentence fragment like that & get rocked back.
Imagine some construction guy from 1700 or even Roebling in 1850 looking at that whole span while some guy in a white shirt, ugly tie, and hard hat says “So yeah, we jacked it up to slip some new parts under it. No biggee.”
Sacre bleu! Increible!
A unique design makes the bridge more vulnerable.This engineer worked on the Memphis bridge a few years ago. https://www.cnn.com/2021/05/17/opinions/memphis-i40-bridge-crack-future-problems-abdelnaby/index.html
M - for Memphis? Apparently they designed the bridge based on the city’s name?
He’s saying that, but I don’t know enough to agree. Particularly that bit about ‘more vulnerable’. Compared to what?
To me, it appears to be a cable-stayed box-girder bridge. Like the bridges here in Melbourne:
Like all cable-stayed bridges, the ‘cables’ are unequal length, and the support comes partly from the the ‘cables’ and partly from the piers.
It’s unusual in that the support cables come from the arch, rather than from pinnacles, but I don’t know that makes it more vulnerable than any other cable-stayed steel-girder bridge.
The WestGate bridge, linked above, did fall down during construction – and that might be linked to it being a ‘more vulnerable’ design. Or perhaps he just means that most old bridges don’t have this kind of modern design, and it’s uniquely vulnerable by virtue of being a modern design, designed with old methods.
I thought it was just chipped paint along that edge.
ARDOT and TDOT have finalized a repair plan.
I’m impressed they’re scabbing on 30ft plates. That’s just to protect the crews. The bridge won’t reopen for traffic until the beam is replaced.
My local news reported a contractor has been hired. https://www.ardot.gov/news/21-148/
Heh heh. Heh. Heh heh.
ARDOT doesn’t have drone photos that far back so can’t either confirm nor deny.
From the article posted above by @PastTense:
The states are relying on the four-lane, 71-year-old I-55 bridge to get cars and trucks across the Mississippi River and maintain the flow of commercial vehicles. Engineers are inspecting the I-55 bridge to make sure it can withstand the heavier traffic.
Good thinking to inspect the 71-year-old bridge that’s now carrying all of that extra traffic. I hope it wasn’t previously inspected by the same guy who just got fired. I wonder if it was the same guy going all the way back to 2016, or if there’s a more systemic problem.
Yes, The 2016 photo looks very similar to 2019.
It certainly seems like the seismic retrofit put stress on that beam. The retrofit project was from 2000-2015. A photo shows the crack a year later. The engineers will be studying this for awhile.
So, for the engineers…
Supposing the crack had been discovered when it was only 1/4 the circumference or less. Could it have been welded up and/or scab plating attached for reinforcement or would it have still been necessary to replace it as is the case now?
No matter when it was discovered there is still the very big question of what caused the crack. If the answer is poor materials in the beam that cracked then fixing or replacing that beam is the solution. But if the answer is massive forces somewhere then other additional changes would probably be needed–otherwise further cracks could well happen.
This thread got me to thinking. This is never a good idea. The Hernando de Soto Bridge (the I-40 Bridge) crosses the Mississippi River but it also crosses the Arkansas Tennessee border. How does each state allocate the costs and responsibilities for construction, maintenance, inspections, repair, etc. for the bridge? I am now wondering not only about this particular bridge but other similarly situated bridges.
It’s a bridge on an interstate. Doesn’t that automatically make it the Fed’s coin?
Even if that’s true, the actual work is contracted by, and/or performed by, the states’ Departments of Transportation (or the equivalent).
It’s been noted in several of the articles that for the two Memphis bridges the agreement is the Arkansas side is responsible for the inspections and Tennessee for maintenance and repair.
I imagine this particular split came because the Tennessee side is the largest city in the state and the Arkansas side is swamp land for several miles. The wear and tear is due more to Memphis than anything else in the region.
In this case, however, Arkansas and Tennessee will be splitting the costs of the emergency repairs. Considering the inspection failures, this is fair.
They certainly don’t just build bridges and figure those issues out later. Those issues are settled well ahead of construction. There’s not a universal method to split costs but it’s often in both states interests in these cases to split costs as fairly as possible - building and maintaining bridges are no-brainers in economic impact.
I quite enjoy the flat/open terrain of West Memphis and it’s environs. A welcome break from the hundreds of miles of more rugged terrain to the east.
Tennessee may well be my least favorite state to drive through.
Kayaker’s photos show crack in closed I-40 bridge in 2016
This was the highest resolution photo I was able to locate at this time, but it’s likely had the size reduced to make it web friendly. I’m hoping to find the original somewhere to see what it looks like zoomed in.
The best I’ve seen is
Much better. Thanks.
Took me two days each way traveling from Arkansas to New Hampshire. I recall the speed limit was 55 or 65 instead of the Arkansas 75 MPH.