Is it just me or is the far crane's barge listing heavily in the direction the crane failed? Otherwise I couldn't see any reason for the crane to seem to uncontrollably swing to that side and ultimately fail.

Maine Professional and Structural Engineer
American Concrete Industries
www.americanconcrete.com

That is what it looked like to me.

See this https://www.youtube.com/watch?v=LyvkUAQ3gHI which is more complete footage.

It seems they're trying to first lift then rotate the bridge section 90 degrees which is when it stats to go wrong. Not clear if the far crane failed or moved due to the lean of the barge, but as it rotates it can be seen that the bridge element is no longer level and then it all starts to go wrong.

The movement of the bridge section looks quite fast to me, especially with a 90 degree turn involved when the cranes are sitting on barges which are far from steady.

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Looked like the CG shift flipped the first crane, the bridge beam hit the second crane and flipped it.

A little bit of barge tilt, a little bit of P-delta, repeat.
There are indeed flotation calculations available to present just this sort of thing. Insurance works also.

A crane is typically is lashed to a barge very securely with wire rope. The worst case should be:

The barge lists, the load swings away from the crane's cab, boom angle with the horizontal decreases. The crane's lifting capacity for this new geometry is lower than it was. The lashings keep the crane in place on the listing barge until the crane boom "folds" which causes the load to fall to earth (or the bottom of the water). Of course this removes the load allowing the barge, with the crane lashed to it, to right itself. But that is with one crane doing all the lifting - using two cranes complicates matters. In any event, the crane operator(s) need experience and "nerves of steel" to manage this fast-moving, controlled failure - it can be done.

For this accident, both of these cranes appear to be undersized truck cranes with hydraulic booms greatly extended. The outriggers on both cranes appear to have been properly extended, but there is no visible indication that either crane was secured to the barge(s). A crawler crane with a fixed-length lattice boom is a better choice for barge work - boom action is more predictable, especially under emergency conditions.

To me, it looks like each crane was on its own barge... as it should be. Also, the cranes appear to have been positioned at the "back" end of the barge... again as it should be. The barges were butted up to each other. Crane work should be performed, as much as possible, over the back of the barge not the sides - minimizes the listing problem. Ideally, the back end of the barge is blunt, not "raked". This gives maximum flotation where it is needed most. On this project, it looks like there was no choice in the narrow water way but to work over the sides.

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Here's an aerial view from the link:

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Nice analysis SlideRule.

Maine Professional and Structural Engineer
American Concrete Industries
www.americanconcrete.com

Thank you, TME.

Here is a link to a follow up story that includes these statements:

Quote:

...called the crane operators “very unprofessional and ridiculously amateurish“, adding that the operation was “doomed for failure”. “Too much risk was taken and bizarre decisions were made.”

Quote:

...the crucial mistake was that the used cranes were not suitable for placement of pontoons. “These cranes are rudderless when the ground is not level. Then the operator can no longer correct the crane.”

http://www.nltimes.nl/2015/08/05/experts-crane-col...

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You can also - in very shallow water like this, simply run pylons (outriggers essentially) down from the barge to the bottom of the canal/river/swamp.

I agree with above: Barge listed as the first and second crane rotated the load from viewer's left towards viewer's right (load passed between the two cranes); the listing (sloped deck) rotated the first crane too far, so it failed (was pulled over) AND slid off of the sloping barge deck; which dumped excess load on the second crane; which then failed.

As the bridge section starts to fall, part of the rigging from the second crane pulls free (top edge). As the bridge section is dropping, you can see the rigging to the second crane come taut. This is when the second crane starts sliding and tipping.

Bill
--------------------
"Why not the best?"
Jimmy Carter

Yeah, the second crane appears to fail mostly due to the impact and eccentric load of the falling bridge piece suddenly engaging the rigging.

Maine Professional and Structural Engineer
American Concrete Industries
www.americanconcrete.com

I realize that analyzing after the fact has its drawbacks, but it seems like it would have been prudent for the contractor to install two or three properly braced outrigger pile off the side of each barge to take any overturning (keeping clear of the pick and swing area). These attachments are used on dredges all the time to keep the barge in place in wind or a current. They could have functioned as outriggers here, bearing on the bottom of the channel (hopefully).

Mike McCann, PE, SE (WA)

I've been trying to work out what they were meaning / trying to do. Looking at a number of other videos on YT, it looks like they meant to keep the bridge deck in its original orientation, then move the two barges, with those two tugs you can see, approx. 200m down the canal ( away from the video location) to where the lifting bridge is. What seems to happen is that the rear crane rotates too early and not in sync with its compatriot leading to imbalance of the load.

The actual error occurs some 10 seconds before you start to see the rear crane move but in actual fact it has been sliding sideways on the rather narrow pontoon until my suspicion is the out rigger fell off the deck causing a sudden movement , but in fact the collapse started inexorably some time before that.

It seems no one has actually died, but no mention of injuries and several buildings and businesses are affected.

The fact that the barges needed to move, with this deck held between the two gives us a bit of an idea as to why the barges weren't fixed in place, but this seems to be a poorly thought out and executed lift, with no real consequence planning

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This video https://www.youtube.com/watch?v=hNq2qbf-RY8 presumably by a drone is taken beforehand, but shows the initial position and the bridge in the back ground. It looks like they meant to lift the bridge section into the middle of the barges then move it with the cranes and lift into place.

The rear crane looks much weedier than the near one which maybe explains why it is so much closer to give it less jib angle??

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LittleInch's video helps allow better speculation:

The bridge component being lifted is the movable "leaf" of a single leaf bascule bridge (drawbridge), similar to this one:





In the videos, the barge away from the camera is narrower and more likely to list than the barge in the foreground.

The crane on the distant barge appears to be smaller (lower lifting capacity) and the outriggers are not deployed as far out as the foreground crane.

The right, back outrigger of the crane in the foreground is almost off the barge deck before the lift began. At the 20 second point in Longinthetooth's video you can see this outrigger fall off the barge deck, accelerating the collapse sequence.

In my opinion, this lift was already out of control in the first frame of the collapse video and should already have been terminated. The distant barge is listing significantly. Because of the distant crane's positioning, this puts side forces on the boom which they are not designed for.

An aside comment: On a barge of dredge the members that go straight down from the vessel to the bottom are called "spuds". They are typically used to position the vessel horizontally, but be cause of tide, current, wave action, change in vessel displacement, etc. allow the vessel to move freely vertically. For special purposes they can be used for vertical support.

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Looking at the drone video, it gives me a "What where they thinking" impression.
On a big crane like that, you expect to have major imbalance in one direction prior to picking up the load, then in the other direction when it's lifted. And you assume that the ground is stable enough to support all that. Generally, the crane load charts don't tell you how tilted the crane can be, and still be stable and swing around and all that. So it looks like somebody maybe just assumed those barges were stable and didn't think to check for tilting there at all.

Slide Rule Era:

I assume the plan was to move up the canal and install the bridge section. How could this have been done differently? Such as not carrying the section vertically? Maybe laying it down on a barge from shore mounted cranes? Then lift to position again by shore mounted cranes?

Quote (oldestguy)

I assume the plan was to move up the canal and install the bridge section.

Agreed, that certainly had to be the intent.

The bridge is located in an urban area. Using crane(s) from the canal bank does not look like an option. Here is a satellite photo:



Other methods that could be reviewed may be:

1. Assembling the leaf in place. That was done decades ago, before very large cranes were common. Probably not cost effective now.

2. Build temporary trestle(s) adjacent to the bridge and use them to support crane(s). Again, being in an urban area limits space. Also, the waterway traffic likely has to be maintained.

3. Reinforce the adjoining bridge spans to support sizeable crane(s). Probably not cost effective.

This brings you back to barge mounted operations. I believe the Contractor was using a workable approach, he just did an unacceptable job of equipment selection and preparation. Each crane was on its own barge, the leaf was on a third barge. Failure appears to have happened when the cranes were lifting the leaf off its barge and standing it vertically on the same barge with the crane in the video background. If the leaf had been horizontal on a barge, it would be too big to maneuver into position. At some point the leaf would have to lifted to a near vertical orientation to be installed anyway.

Barge width is limited by bridge dimensions on the canal. More consideration of existing project site limitation may have allowed smaller modular leaf components to have been designed and assembled on site. Then smaller cranes could have been used - but that is hindsight.

This job, as fabricated, could have been accomplished in the way the Contractor planned. It would require much more attention to detail and careful execution.

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Longer video of the collapse: https://www.youtube.com/watch?v=8_nTLIuk6Hk

Maine Professional and Structural Engineer
American Concrete Industries
www.americanconcrete.com

After looking at both the video taken an hour before the accident and the longer accident video, it appears to me that someone didn't properly determine where the center of mass of the combined cranes and the suspended load was going to be after the bridge section was moved onto the barge, which apparently was going to be used to move the bridge section, while suspended in what I assume was going to eventually be a horizontal orientation, to the bridge site. Once the section started to twist you could see the guys holding the guide stays suddenly turn and run back away from the moving load. I think that was the point-of-no-return and momentum simply took over as the center of mass moved past the center-line, and even before it bumped the boom of the far crane, the barge began to list which condemned the entire operation.

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To an Engineer, the glass is twice as big as it needs to be.

The boom for the first crane seems to be moving way to fast, just prior to the load tipping over. I would think that something broke in the crane. You can see that the body of the crane is quite stationary while the boom is moving a lot, and the body doesn't really start sliding until the orange pieces of the load hit the deck of the barge.

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There is another video on U tube showing the removal of the old lift section from this same site. The old section was blue-green color and no counter weight. Work was very slow, placing on a temporary support as it sat inclined. No barge tilts then.

It would appear that the intent for the new section transport to the bridge site would be with the section sitting in exactly the same leaning position as it sat on its
first barge, probably with a re-use of its temporary supports, out in front of the far crane, parallel to barge.

Here is the link:


https://www.youtube.com/watch?v=jSh8CYSYEAc

This cell phone video shows what I was talking about: https://www.youtube.com/watch?v=n5fyE_TiP0s Since the barge doesn't yet tip until the boom is mostly all the way down, I think something actually broke in the boom.

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IRstuff - I agree with you about the boom collapse while the crane body remains upright. A crane boom can resist very little side force. The unanticipated geometry of the loading probably caused the side forces. See this video of the collapse, taken from another angle. At the 41 second point of the video the sideways boom movement that you noticed really accelerates. At that time it looks like the barge is listing, maybe 20 degrees:

https://www.youtube.com/watch?v=rXv5cfX3rbg

oldestguy - Nice video. There is another video of that 2011 lift that shows one crane on a barge, the other on the bridge deck. Note that the barge mounted crane works almost exclusively over the length of the barge, not the sides. At one point the barge crane does swing horizontally to about a 45 degree angle, but that is all. As you noted, without the bridge counterweight the load would have been much lighter.

https://www.youtube.com/watch?feature=player_embed...

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That's funny I think. the first link is the actual first video right-left reversed, so it's not really a "new" angle...

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Those 2,000 EUR of "pre-compensation" per damaged/demolished house are simply amazing. Are they joking? It's as if they hit the house(s) with a collapsing crane once again.

Dejan IVANOVIC
Process Engineer, MSChE

Interesting analysis here http://youtu.be/7CfeRBGKMjM pt 1 and here http://youtu.be/FClRoFJ7Xco pt 2

Couldn't find any news on repairs or what has happened since. If anyone has anything it would be good to see what they've done.

also if your interested in crane accidents there's always this to keep up the attention: http://www.craneaccidents.com/

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The Dutch Safety Board is conducting the investigation. It could be a few months before a preliminary report is released.

Here is the link: http://www.onderzoeksraad.nl/en/onderzoek/2143/top...

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