Mike270412
Golden Boy
Let's hear from all you armchair engineers. What the fawk happened?
The bridge.
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it bent
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What bridge?
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Mike270412
Golden Boy
Thanks for clarification .I Wasn't quite sure.
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Mike270412
Golden Boy
The bent one.
ferniesnow
I'm doo-ing it!
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Was the bend convex or concave?
Lund
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Put together on a Friday afternoon
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tiger666
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It looks to me like crane operator error.But I bet the crew gets there peepee slapped because crap flows down hill and the grunts are always on the bottom.
imdoo'n
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truckers!!!!
turned corner to sharp
turned corner to sharp
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Bigblack
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Installed in cold weather between immovable piles...warms up...bends. Just guessing. Usually single span bridges are only fastened at one side and the other side rides on a bearing plate that allows movement.
maxwell
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how so?
Girder installations are serious business and supreme is the best at it. ( girder supply and erection is typically a one contract item). from the limited details i have and a few photos my conclusion is as follows. This bridge is a single span bridge with 3 girder sections. east west and centre. This means there are no piers for the girders to cantilever and the east and west sections must be temporarily supported past the centre of gravity and chained down at the abutment ends. followed by complete cross brace installation on those completed sections before the centre girders are installed and cross braced. the girders that twisted are in the center section. Steel girders are extremely flimsy in torsion and are designed for only downward force. only when the entire girder structure is cross braced and the concrete deck is cast onto the girders does it become full strength in torsion (earthquake), side load (wind) and down force (vehcles). as girders are installed a team follows quickly behind and installs cross bracing but does not torque all bolts until complete. my "guess" is that the weight of the centre girder sections installed combined with warmer temperatures caused the temporary shoring to sink. This could even be by as little as 20mm to cause this. from the photos you can see the cross bracing team was not able to completely cross brace the damaged section before this occurred. if the shoring did in fact sink this would put extreme amounts of compression on top of the girder and tension on the bottom of the girder causing it to buckle. had they been able to fully cross brace the centre in time this likely would not have happened but it still could have due to the amount of force. In my opinion this is not a matter of poor quality steel ( this is checked and double checked before fabrication and shipping). it is also in my opinion not a fault of the installation crew but more an oversight into the temporary shoring systems in place. i would like to think i am wrong and it was something else because typically all things are considered such as temperature while the contractor and engineer are developing and approving a girder erection plan. I also have a hard time thinking this is a design flaw in the girders for 2 reasons. #1 the girders sitting with no concrete deck or traffic have less than 20% of their design load on them and i dont think they could have fawked that up that bad. #2 the computer software used to design girders is mind blowing. they run them through dynamic and static load tests, wind, earthquake etcetc tests before they are fabricated.
Just my 2c
maxwell
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what do you mean by this? you are correct somesingle span bridges are designed that way but others also slide on both ends. none of us have drawings so its hard to make that assumption.
That is some extremely strong forces to bend those beams.
The above post makes sense, but then why didn't the others bend?? If that lateral bracing held up, then something else would have to break or bend.
I beams aren't meant for lateral forces. But what could push on the side of the beam to bend it like that? They said it bent before their eyes.
Regardless, someone dropped the ball on this one.
The above post makes sense, but then why didn't the others bend?? If that lateral bracing held up, then something else would have to break or bend.
I beams aren't meant for lateral forces. But what could push on the side of the beam to bend it like that? They said it bent before their eyes.
Regardless, someone dropped the ball on this one.
Bigblack
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Why I said "just guessing". I don't live in Edmonton...looks to me from the pictures that there is a steel piling at each end of the horizontal beams...jus' guessin'....
bingo1010
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what about wind and harmonics.....combined with what max had to say about lack of crossbracing during installation??
maxwell
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i forgot to mention this. hard to tell by the photos but those centre girder sections are larger than a greyhound bus. wind was almost guaranteed a contributing but likely not the only factor.
maxwell
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kind of. if you connected all 3 girders east, west,centre and lifted it onto the abutments it could support its own weight. but seconds later the centre section would flop sideways just like in the photos just due to the sheer weight of the girder. like i mentioned earlier these things are incredibly flimsy in torsion by design for weight savings once all girders are cross braced together they become one solid unit which is now torsionally stable. I am not a structural engineer just speaking from my bridge building days as a project manager.
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