https://www.tn.gov/tdot/news/2021/5/17/tdot-awards-contract-on-the-i-40-hernando-desoto-bridge-repair.html[/URL]]We now have a webpage dedicated to the bridge repair:
First thing I would do is to find the cause, and if there are other locations where this could happen. I've not seen a failure like this and I'm not sure why it happened. Then I consider the manner of fixing it.
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
Per one of the TNDOT press releases, sequence is something like
[ul]
[li]Stabilize the crack[/li]
[li]Design permanent repair[/li]
[li]Install jig to allow installation of replacement beam[/li]
[li]Install replacement Beam[/li]
[/ul]
If more cracks are found - repeat as many time as necessary.
Reopen for traffic
Design of the permanent repair should take into account understanding the cause of the crack, to prevent a repeat.
I'm not into bridges, but the crack is very unusual IMHO; it should have cracked at the first line of bolts. It's odd that there would have been a joint at that location. Other than making things temporarily safe, my first objective is to find out why it cracked, else repair may only be temporary. I'm surprised there wasn't a catastropic failure.
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
Is this beam two C-sections with plates welded top & bottom? Given the photos by IRstuff & the ding in the drain pipe noted by SparWebl, what are the chances that during a past inspection, the snooper truck smacked the beam while looking at the beam splice and initiated the cracked weld shown in IRstuff's photos?
^ based on the box beam having 1-3/8" (35mm) vertical plates and 1/2" (13mm) top and bottom plates, it takes away from the theory the shear lag is the culprit (with the connection on the vertical plates only.
The source is more likely the weld that formed the box. By the 1970's, they should have been smart enough to not have stitch weld connecting members on a cyclically loaded structure. There is a close up photo above, it looks like the thinner top plate runs over the vertical plate about half way, and it's connected by a fillet weld. That shouldn't be a too bad fatigue category.
Or it's more likely to be stationary or slow moving on one carriageway and moving freely on the other?
The original Severn bridge had that issue when the queue for the toll booth backed onto the bridge on a regular basis on one side. They worked out that in strong winds the thing could fail. They partly solved it by making the tolls one way, hence the issue that you paid to get into Wales, but it was free to escape. tolls all gone now.
But uneven loading probably wasn't thought about in 1970...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
yep that's what my theory revolves round. Basically one side is different loading to the other possibly including ROT degree of freedom as well as the main axis. Condensed traffic heading into town slowing down, Out of town everything accelerating and much lower load density.
Severn this bridge and KGV all built in the same period.
The Patroon Island Bridge (Interstate 90 over the Hudson River in NY) opened in 1968. It has interchange ramps just west of the main span. It's also downhill approaching the ramps.
Cracking in the floor beams was attributed to trucks braking for the westbound offramp. IIRC, braking forces were twisting them.
My glass has a v/c ratio of 0.5
Maybe the tyranny of Murphy is the penalty for hubris. -
So it could have been fatique... could the clamping forces from the bolts on the plate have attenuated the stress to cause the failure to occur outside the bolt holes... I would have thought the crzck wouid be at the first line.
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
I don't think uneven loading would be the case but I definitely could be wrong. This is an arch tie and should be absorbing the majority of its vertical force loads from the arch bearings. By the time live load makes it to the bearings, I suspect there has been adequate redistribution through that truss arch.
My thought is that since the tie is also the chord member for the lateral system, the design didn't account for lateral forces in fatigue stresses. AASHTO Bridge Design Spec really only evaluates truck loads in fatigue. But with this being a long span and susceptible to large wind loads - there is a stress range there as well. That's where my guess is without having ANY knowledge about bridge design standards in the 60s.
