Vertical lifting... How not to...

[Archer]

This happened a few days ago in The Netherlands. The moving part of a bridge needed renovation and a new section was going to be lifted in. Things did not go as planned.

http://youtu.be/j-MMIWpyTMw

Fortunately there were only minor injuries, no fatalities unless you count one dog. Incredible really. Several homes are wrecked though and it will take a while to clean up. Lessons will be learned from this.

[Vancouver]

It made our local news.

[Airspeed]

Heartbreaking, all the work gone in seconds.

[Dev One]

That surely was always going to end in tears. Just consider the change in C of G on a floating platform & using two cranes that are not fixed to the platform!!!
Keith

[ChrisHunt]

Yep, didn't look good from the start and add to that a reasonably high wind speed...

Whoever signed off the lift plan needs his head examining. The amount of grief I have to go through for lifts a fraction of the weight and complexity of that one. Also not entirely sure what they expected with the weight of the bridge section removed from the barge even if the lift was successful. I noticed that the cranes and bridge section had been positioned so as to cancel each other out weight wise so the most likely outcome would have been very similar.

[Archer]

Sounds like you know a thing or two about it, I don't I'm afraid but my mechanics and logic sense are still trying to make sense of it. I think that the plan was to get the section between the two cranes, then move the barges further back towards the bridge and shift the section to the right into its slot.

When you say that the cranes are positioned to cancel out the weights, how do you mean that? With the section left of the crane bases, wouldn't you always get more weight on one side of the barge?

[ChrisHunt]

Purely from the evidence of the video there seems to have already been too much weight on the RHS side of the barge as we look at it and when you take into account the change of CoG as the lift progresses. The lift was in trouble before the bridge section reached the centre point of the barge. The RH crane was already showing signs of instability fairly early in the lift (excessive movement at the tip of the jib). It was a hugely ambitious lift, it's extraordinarily difficult to get two cranes working in tandem like that - add lack of solid foundations, wind speed (sail effect of the bridge section) and you have all the ingredients for a disaster.

As for post lift stability the pre-lift weight distribution looked to be pretty even (it would have to be) but if you take away the weight of the bridge section then you're left with the majority of the weight on the RHS of the barge - I suspect the cranes would have been in difficulty in any event as soon as the weight of the bridge section came off the barge. They might have got away with it but looks touch and go. The Dutch have some superb engineers but it's difficult to believe they had the right man for the job in this instance.

There's a link on the same page to a whole series of crane mishaps - in the majority of cases the lift was an impossible task to begin with or they had the wrong tools for the job. When your crane jib looks like a fishing rod with a bite you know there's going to be only one result.

[Archer]

I think it is pretty clear that this was the wrong man for the job

Interesting to hear your take on it, thanks. I would have guessed the wind to be pretty mild but now that you pointed it out I agree that the sail effect may well have been more than I would have guessed.