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.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA Siemens PLM: UG/NX Museum:
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.
TTFN
faq731-376
Need help writing a question or understanding a reply? forum1529
Of course I can. I can do anything. I can do absolutely anything. I'm an expert!
There is a homework forum hosted by engineering.com:
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.
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:
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.
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.