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The I5 Skagit River bridge just collapsed


tvashtarkatena

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holy shit. I used to boulder on rocks glued to that same concrete wall support. (other side of the river) I remember being kinda freaked out that some security would bust me as some kind of terrorist. Luckily for me and my alibi, it has been 2 years since I was last there.

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there are possible detours both east and west of that bridge. college way on south of the bridge to another river crossing and back on i5 near the costco. And a bit longer in the scenic west side of the town in the tide flats tulip country.

Prolly good ways to go in the wee hours of the night. Jam packed in the day.

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The bridge design is a series of triangular and inverted triangular trusses with low, curved horizontal beams directly above the roadway connecting the two sides. This was the entrance span at one end of the bridge which collapsed. According to a bridge survey of the span it was rated functionally obsolete, in part because of the design due to trucks hitting the low side of the first entrance horizontal.

 

The force of a hit there would be immediately transferred to the beams supporting the roadbed by the second sidewall diagonal beam which terminated at the spot the roadway collapsed.

 

Speculation is that the outboard (passenger-side of the slow lane) of that curved, overhead entrance-span horizontal took repeated truck hits over time, basically jack-hammering the roadway support beams each time and eventually weakening them to the point of collapse.

 

Think carabiner 'micro-fractures', but for real, and probably combined with stress corrosion cracking.

 

 

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Would imagine the first span on the other end of the bridge has also taken hits so it's probably not just a matter of repairing the collapsed span. Even if they attempt to do that I would guess the whole rest of the bridge will have to get a retrofit before they'd let traffic on it again. Does sound likes it's going to be a way extended clusterfuck. At least there's a nearby bridge they can reroute with.

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The Washington State Patrol said the truck driver works for Mullen Trucking in Alberta. The tractor-trailer was hauling a housing for drilling equipment Vancouver, Wash., when the top right front corner of the load struck several trusses on the north end of the bridge, the patrol said.

http://www.cbsnews.com/8301-201_162-57586034/bridge-collapse-in-washington-state-blamed-on-tractor-trailer/

 

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Wow, I hadn't seen pictures of this before clicking on that link. Its remarkable that no one died.

at the least, i suspect target has been able to sell some folks a few new pairs of underwear :)

 

my question: did the truck that struck the upper-supports escape, and if so, why? :)

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The truck did make it across and with only a small dent in its load (impact point circled in blue below). I'd

guess off hand the bridge deflected considerably before the collapse which probably would have given the

whole experience a real 'slo-mo' feel. The roadway also likely 'folded' and 'tore' from the hit side of the

bridge on across the roadway like a zipper which would also have slowed things down a hair.

 

Couple of interesting points from recent photos: first, is the role corrosion played in the collapse,

check out the points where the beams bent - most of them had recently been prepped for painting due to rust (green circles);

second is the fact the bridge had no strap or block siesmic retro-fits of the kind done throughout downtown PDX

bridges after the Oakland quake so the bridge section ends just slid off the piers with no resistance (yellow circles).

 

I-5_bridge.jpg

 

i-5_bridge_-2.jpg

 

i-5_bridge_3.jpg

 

i-5_bridge_4.jpg

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I heard DOT officials are also looking to question two pigeons who landed on the bridge at the same time the trucker struck the bridge, thus ultimately causing the who rotten thing to collapse. The hope is that the pigeons are insured.

No worries though, a cheap third world solution has been found: Sink old semi retired WS Ferry horizontally in the river and secure with sunk motorhomes and rail cars. Attach gang planks to shore and have traffic drive straight through!

 

 

 

 

 

 

 

 

 

 

 

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Actually Joseph, in better photos you will see that the orange areas aren't primer, but where the top coat of paint flaked off when the beams bent. At least that is how it looks to my eye. I drive on the bridge a lot (or used to), and I didn't see any primed splotches in the last couple of weeks, nor crews working on it in some time.

 

Great ideas Scott! Are you a consultant for WSDOT now?

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Jason, great point. If that's the case then it's good to know the original primer did at least work and didn't come off in sheets as the paint did. And if corrosion played no significant role then I guess it does just further point to the basic failure being that the truss beams were way under-spec'd for the job all the way around. At least you look at the first aerial shot, all of the beams look like they were designed 'to the bone' with no margin for anything going wrong.

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This is going to wreak havoc on the State Ferry system in and out of Anancortes, not to mention regular traffic from Mount Vernon, LaConner, and Oak Harbor.

The Skagit Flats roads will be jammed.

 

Also, the Mount Vernon to Everett commuters? Better leave early and come home late.

 

Major trucking corridor for US/Canadian goods, additionally.

 

This is going to be a rough 4-5 months.

 

Glad everyone was OK.

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I've suspected this may be an attempt by the extremist Skagit/Whatcom ski mountaineering cell to initiate jihad on the tribes to the South and interfere with our traditional migration trails to the north just before the summer ski season starts. This "Septula" guy in particular is probably on the Homeland Security watch list. :mad:

 

Why don't they just install a ramp on each end of the remaining span?

 

[img:center]http://fwallpapers.com/files/images/dukes-hazzard-6.jpg[/img]

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