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Rural Bridge Collapse Immediately After Opening 16

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Shotzie

Structural
Feb 12, 2016
156
CA
Link, the article claims that excessive pile settlement caused one of the spans to collapse.
 
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"it wasn't structurally faulty." So was it sub-structurally faulty?

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. -
 
>>>Hicks called it an “act of God,” insisting the bridge was built to standard.

“Something underneath the riverbed just gave way,<<<

“It wasn’t structurally faulty. The fault is in what God did under the river.”

I don't think God had anything to do with it. Sounds like someone didn't bother with drilling any boreholes to find out what they were founding the piles on...

"It would appear that the visible piling shifted away from the joint it was supporting."

The pier seems to have sunk several feet, so the center span wasn't long enough to reach the pier cap anymore.
 
Root cause found:

“They (the engineering and construction contractor) don’t know if there’s an air or gas pocket or underground river or whatever,”
 
You can almost see them Duke boys coming down the road :D

bridge1.jpg


Seriously though. Those steel girders look a bit narrow. Should an old multi-span bridge like that rely on the shear strength and integrity of the beams at the supports?
 
Those look like concrete box beams to me.

Edit: Sorry, were you referring to the pier caps? Those do look a bit narrow as a seat for the beams.
 
I was sure it's not April yet.

That sure looks like the old bridge. "Timber substructure with concrete girders" is how the old structure is described on the demolition site and that description fits the picture.


 
Article says a 15 foot span?

BS. The writer's dyslexic!

I see what l;ooks like wood framing, but can't be sure... and would not make sense. Must be the coloring.


Mike McCann, PE, SE (WA)


 
The RFP stipulates that the roadway could potentially be reused, while the main objective was to replace the wooden pilings

In any case, sounds like there's at least one PE about to lose their license.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
I don't see anything that suggests the road or bridge deck was touched in any way recently.

How do you drive a pile from under an existing bridge?

Or do you think they just rested the thing on the creek bed and called it good?

 
"How do you drive a pile from under an existing bridge?"

Maybe that is the problem; if they left the roadway in place, they couldn't have driven any new pilings and everything might possibly be sitting on the original, wooden pilings, and the new ones slid off the old ones. That would a bankrupt-inducing suit in the making. If they removed the roadbed and drove new pilings, that would be different.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
It sure looks like something shifted the bottoms of the steel pilings out farther into the stream - they don't look vertical anymore, as if they were set on a single submerged block that rotated. I am impressed that the diagonals held them all together and they remained in one plane.
 
bridge1-1_hvo5ps.jpg


The photo shows a ridiculously undersized pile cap. Not saying it isn't "strong" enough... it is too small, specifically the flange width of steel section. A (concrete) pile cap for a bridge of that size should be double or triple the width of that flange. The end of the span that fell is likely the expansion end and was not anchored (by design) to the pile cap. Probably slipped off, perhaps bending the flange, got wedged in place, slowly "pushed" the pile bent out of the way, then collapsed.

Steel section was probably used for the pile cap, instead of concrete, to lower costs.

[idea]
[r2d2]
 
Is that a layer of gravel on top of the concrete?
If so, that could have increased the loading on the piles.


Bill
--------------------
"Why not the best?"
Jimmy Carter
 
It looks to me like the remaining section of roadway on the far side of the creek is hanging out over the pilings cap (toward the middle of the creek, where did the piece that fell sit) on the down stream side. ???

Although the second pilling from the left looks as if the concrete roadway beam slide down the pilling possible pushing it outward toward the creek bank. Same for the far left one.
 
It seems to me that both piers shifted sideways, but that could have been the result of the collapse of the center span, rather than the cause of it. Extrapolate the line of the top of the deck for the near span in the picture, and it becomes obvious that the near-side pier is a few feet lower than where it should be, as was stated in the story (granted, that may be the only thing they got right). When it sunk, the distance between the pier caps increased, and the beams slid off the seats.
 
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