Never seen or heard of anything like this. Wonder if the abutments are too stiff and not allowing thermal movements, causing internal compressive forces in the superstructure. Then once the deck was removed and not there to share some of the compressive loading, the girder turned into spaghetti.
I have seen something similar before, but the beams were in between concrete retainig walls.
The issue was that the beams without composite deck were too weak for thermal compression.
Of course, this should be check before the deck was removed.
As my old professor used to say to some students:
Beekeeping is such a good job. Why are you trying to be a bridge engineer?
Missouri is a good as place for this than many. Right now Missouri is engaged in a large bridge rehabilitation/replacement program, called the Safe and Sound Program. Over 800 bridges are involved and of those about 300 are straight bridge deck replacements. So chances of seeing bridge deck work in Missouri are pretty high right now.
Some observations:
1. Bridge appears to be of some length, more so than typical highway grade separation.
2. Terrain to each side is woody giving way to a clearing in the middle (if there is one) indicating this spans a creek and overflow area.
3. It appears (though my eyesight isn't great anymore) that the bottom flange is variable. This seems particularly so in the second photo, where teh photographer is closer to a pier. You can see multiple bearing stiffeners on the inside right hand girder. Bottom flange coming into the pier appears to be flat and then dips into the pier and climbs back up and away from the pier toward the background.
4. You can see a change in the diagonals over the pier for the deeper web.
5. Lots of intermediate diaphragms or crossframes.
6. Majority of the deformation appears to be in the mid-span where the shear connectors are. An obvious area of compression for the top flange.
7. The abutment is, for all practical purposes, serving it's function of integral nature. Allowing no independent movement or rotation of the girders and abutments.
Back in the day and perhaps still in practice today, the top flanges of composite bridges were made the minimum allowed by AASHTO, usually 12" x 3/4" or 5/8" way back when. It was assumed that due to the composite nature of the deck and girder nothing larger was necessary.
Though there appears to be many diaphragms we're looking straight on and can't really judge spacing. So if the diaphragms in the composite area are greater spaced than in teh foreground (and by design they would be) it's possible that by removing the deck and not allowing expansion, the upper portion of the girders buckled.
I have some contacts in Missouri and will pose this to them to see if it is in Missouri and if so, what the conditions are.
wiktor - I used to have a professor who would staple a KMart application to failing student's exam papers. I don't think that would go over well in today's PC world!!
Regards,
Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
All - I was able to confirm that the bridge is in Missouri and that lack of movement is cause. The concrete diaphragms are being chipped out to provide movement.
Regards,
Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
Intersting...I can tell you the contractor's proposed solution to beam straightening: hook a dozer to each end and pull!
In addition to dealing with the beams, I suspect they will have to cut anchor rods, or other conntections between the beams and substructure, and then reset and reattach the beams.
Can you give me the contact at MoDOT that I can talk to about this particular bridge? I have a colleague who has written numerous articles and books on integral and semi-integral bridges and would like to talk to someone about this particular situation and the possibility of using some of these photos. Thank you!
Looks like the only bracing in the horizontal plane was the deck. The loading could be a combination of thermal and inward deflection at the abutments. Interesting that the beams buckled into a wiggly worm rather that globally.
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