Wednesday, April 15, 2015

just 23 years ago this bridge was made, yesterday, it fell apart, and killed this young couple and their baby. Can the transportation dept pay attention to our crumbling infrastructure now?


above is the far side, and what it had looked like, notice the top half, which I will guess is the hip high wall to keep vehicles from driving off the bridge sideways... a K Rail is one term for it, Jersey Barrier is another


here you can make your own estimation how much of the bridge tumbled over onto the truck below, at 9.8 meters per second squared... about 1.5 seconds from the instant it parted ways with the bridge to crushing the passenger compartment of the truck.


http://www.dailymail.co.uk/news/article-3037982/Young-couple-baby-son-killed-chunk-CONCRETE-falls-Washington-state-bridge-crushes-pickup-truck.html

Daniel, an construction inspector (who knew one was reading myblog ?!?! ) offered his experience to comment:

I have to disagree with your headline implying that accident was due to structural deficiency.

This looks like it happened during construction of a new sidewalk which was on top of the overhang, adding 532lb +/- per linear ft of bridge (assuming 6' wide & 8" deep).

The contractor had kick braces and overhang forms in place, which is practice for placing fresh concrete.

It also looks like there is a saw cut down the edge of the deck along out side beam and no exposed reinforcement.

My guess is that the contractor expected the kick braces to hold everything up until the could complete the saw cut and crane lift the deck portion and Jersey barrier off the side in a couple of lifts.

To me -this looks like contractor negligence not a rotten bridge. The quoted sufficiency rating of 95.3 is a measure of how well the bridge services the road way, items such as alignment, no of lanes and clearance. The Structural Rating is the number everyone should be concerned about, rating of deterioration of structural members, deck, impact damage and erosion.

I do agree that our highway infrastucture needs a massive amount of attention but that is not what is at fault in this case. 

6 comments:

  1. I have to disagree with your headline implying that accident was due to structural deficiency. This looks like it happened during construction of a new sidewalk which was on top of the overhang, adding 532lb +/- per linear ft of bridge (assuming 6' wide & 8" deep). The contractor had kick braces and overhang forms in place, which is practice for placing fresh concrete. It also looks like there is a saw cut down the edge of the deck along out side beam and no exposed reinforcement. My guess is that the contractor expected the kick braces to hold everything up until the could complete the saw cut and crane lift the deck portion and Jersey barrier off the side in a couple of lifts. To me -this looks like contractor negligence not a rotten bridge.

    The quoted sufficiency rating of 95.3 is a measure of how well the bridge services the road way, items such as alignment, no of lanes and clearance. The Structural Rating is the number everyone should be concerned about, rating of deterioration of structural members, deck, impact damage and erosion.

    I do agree that our highway infrastructure needs a massive amount of attention bu that is not what is at fault in this case.

    Sorry to be so wordy, I do construction inspection and maintenance inspection of bridges for a living

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    Replies
    1. no! Don't apologize, you're welcome to weigh in, and I'm glad you have. Your knowledge of this stuff far exceeds anyone else reading along, and this blog is better off with your input

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    2. Following up on your info then, with no flagman controlling traffic, this is going to be a manslaughter charge real quick.

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    3. I kind of doubt it. You are allowed to work over live traffic, so long as pretty strict safety safety guidelines are observed. You are not allowed, under any circumstances, to crane lift any thing over live traffic, ever. Which makes me wonder if the contractor had installed the braces and made the saw cut ahead of time in order to reduce his cost in renting a crane and maint of traffic. The part I can't figure out though, is why they cut the edge of the deck off just to add a sidewalk. A full depth saw cut, cuting off all the reinforcement doesn't leave anything to lap new reinforcement with for a new deck overhang.

      Please keep in mind that all of this I've said is just speculation based on experience and some grainy photos

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    4. - just figured out that whole saw cut thing! The contractor made the saw cut, at the base of the barrier, parallel with the top of deck to remove the existing barrier. Contractor likely had completed the saw cut down most of the length of the bridge and then bumped the now unattached barrier with a piece of equipment. . . . over it went.

      Why remove a perfectly good barrier? -The exist barrier would have to be removed due to the addition of sidewalk, the Jersey barrier shape starts 2" above surface & would need to be raised, along with the min height at top, to compensate for the 8"+/- higher surface of the new sidewalk. new reinforcement would be dowled into deck for securing new barrier to deck.

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    5. I repeat, thank you for your expertise! The rest of us are guessing and shaking our heads. I still think they'll get sued for involuntary manslaughter: Involuntary Manslaughter
      Involuntary manslaughter is the unlawful killing of another human being without intent. The absence of the intent element is the essential difference between voluntary and involuntary manslaughter. Also in most states, involuntary manslaughter does not result from a heat of passion but from an improper use of reasonable care or skill while in the commission of a lawful act or while in the commission of an unlawful act not amounting to a felony.

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