Who Broke The Bridge?

[Diggin It]

Cracked Memphis Bridge Indefinitely Closed, Disrupting Supply Chain

Arkansas officials said it had the potential to become a "catastrophic event," adding, "The bridge was closed to vehicular traffic and the river was closed to barge traffic as a safety precaution."

www.npr.org

Will some of you blame the Russians? Or the Chinese? Iranians?

Or maybe the three legged, eight eyed space aliens from the 17th realm?

 

[BravoXray]

Who to blame? Probably whoever was supposed to inspect it on a regular basis, or did not inspect it in a thorough manner and missed the impending signs of failure.

Probably a combination of corrosion and metal fatigue.

At least they caught it before it collapsed and killed people.

 

[oosik]

There are people who owe a debit of gratitude to those who finally pulled the plug. Inconvenience tops sudden death every day.

 

[ArlyA]

I can't tell from the photo just where this memeber is located,,, just the same, does not look like it rusted away to me.

 

[oosik]

Right Arlyn - looks more like some type of stress fracture. The bridge is simply pulling apart. What type of construction method relies on rivets and not welds. I wonder - is this bridge old enough that welding was not available when it was constructed.

 

[dusty3030]

Bridge was built late 60’s.
gets inspected every two years.
This is a major headache to trucking. The other bridge here on the TN side leads to a restricted truck route. There is a low overpass (13’ 6”) on the section of I55 right after you cross going southbound. Trucks higher than that are going to have to cross at Cauruthersville MO

 

[ArlyA]

I google it to see its a suspension bridge. Diagnosing the stress on that beam, is above my pay grade..

 

[Diggin It]

With no traffic ON the bridge, I would think there would be less threat to barges passing under it with speed controls and USCG monitoring.

 

[fried1765]

With no traffic ON the bridge, I would think there would be less threat to barges passing under it with speed controls and USCG monitoring.

There is absolutely no danger to barge traffic, with all bridge traffic already prohibited!
Somebody is playing the 2021 game,...... like wearing your mask outside, after being double vaccinated.
2021 is the year of total silliness!

 

[ruffdog]

Right Arlyn - looks more like some type of stress fracture. The bridge is simply pulling apart. What type of construction method relies on rivets and not welds. I wonder - is this bridge old enough that welding was not available when it was constructed.

It seems the rivets held just fine......now, about that weak spot in the beam.....

 

[2LaneCruzer]

Chinese steel...

 

[dusty3030]

Chinese steel...

Doubt that. They started construction on it in 1967.

At this point who knows exactly what caused it. The fracture is near the center pier so right smack dab in the middle of the bridge. The bridge itself is over a mile and a half long. The spans between piers over the river are around 1,000 feet long. So the break is at end of a 1,000 foot span.

We had record cold for an extended amount of time this past winter. They did a ton of seismic retrofitting and upgrading to the bridge over the past 10 years or so. They supposedly upgraded it to withstand a 7 plus earthquake since we are in the New Madrid fault zone. Did any of this contribute to it? Who knows at this point.

Hopefully they'll reopen river traffic this week. I watched the press conference yesterday and the chief engineer for TDOT said they were running calculations to understand just how stable or unstable it is at this point.

 

[ArlyA]

Some engineer my have got a decimal off. Not likely because it was cool for a few weeks. Things do break sometimes.

 

[caver]

They call it a crack...I call that a break.

 

[PILOON]

That beam is 24" X 30" and cut clean thru.
Yet they call it a crack?
That is a break!
Clean one at that.

The sound of that box beam popping must have been heard for miles around.

Also , from photos, there is also a minor gap between the 2 sections as well as some deflection.
That suggests there might be a lack of expansion joints somewhere along the line.
It took some major stresses to snap that huge box beam!
Earthquake?

LOL, next they'll blame bird poop that caused corrosion, but actually not so funny as that has been the cause of some bridge failures. But this structure does not seem to offer bird nest opportunities.
Usage of rivets was common practice and has the advantage of not annealing the metal either.

Guess they would next want to Xray all the other similar locations for safety sake.
But then all those suspension cables did a fine job holding things up.

 

[Larry Caldwell]

With no traffic ON the bridge, I would think there would be less threat to barges passing under it with speed controls and USCG monitoring.

Engineers are working long shifts trying to figure out if the bridge can hold itself up. That fracture is near the center of the span, and it's going to take some work to decide if it can stand repairs or needs to be demolished. It may possibly be able to support reduced traffic, but probably not any truck traffic for months. Barge traffic will resume when they are sure it won't fall down by itself.

It was inspected late last year and the fracture did not exist then. This is a recent failure that may affect other structural members.

 

[dodge man]

Let’s see, I had a structural analysis class in 1983. I think the moment around the pier is = to the dead load + the live load divided by the square root of pi. The answer is 3.

 

[Darryle]

Totally unrelated, but how do they set the rivets on a beam like that?

 

[Streetcar]

I google it to see its a suspension bridge. Diagnosing the stress on that beam, is above my pay grade..

Tied arch bridge not suspension
Bolted not riveted
Failure appears to be fatigue at weld
Beam looks to have minimal rust and section loss

 

[Streetcar]

FYI the last major river bridge that used rivets was completed in 1963