Great and clear analysis Peter. A contributing factor might have been that there was apparently hardly any safetymargin on the smaller crane. At the boom's lifting angle, the smaller (400 ton-liebherr) crane is rated lift no more than approx 150 ton. The bridge weight is 175 ton. Looking at the crane lay-out, the smaller crane end up lifting more than half of the bridge's weight. Experts say that the crane may have gone in an emergency mode where the operator had no control anymore and the crane computer takes over as a safetymeasure. This safety may have switched on due to the rotation of the pontoons or due to unpredictable and unequal lifting forces. The crane operator had no time to override the safety and to drop the bridge back on its original ponton. Witnesses say the operator left the crane before the bystanders were even able to see something was starting to go wrong. There is one thing that puzzles me, and that is the sharp opposite jerk of the boat at the far end about when the bridge hits the boom of the crane. Did one of the mooring ropes break? Although the ponton was tilting, it looks unlikely that this would give a major additional stress on these ropes the way they were attached. Still there was apparently a (another) force acting on the boat...
+Alwin van Dongen I wondered also, why that boat at first is going with the pontoon and then suddenly is getting upright. But IMHO that had no effect for the cranes themselves.
Is there a load decrease on the left crane instead of the right? Just exaggerate that the left crane turns furher than the load rotates indeed further and further underneath the right crane which explains why the right crane starts to rotate first. Is there by the way any video evidence that the left crane indeed rotates down due to less uplift by its barge?
NIce theory, but the assumption that the excentrically loaded pontoon will lower at the side of the 700t crane is not in accordance with the footage. Further, because of the weight of ballastwater, it is not necessary that the pontoon lowers at the side of the crane. It all depends on the distribution of loads on the pontoon.
+m20anker Take a look at 1:02 - the pontoon in the front sank deeper into the water. Then they did not pump enough ballastwater into the stern, to keep the surface even. Due to the long boom of the crane, the top of the crane will move a longer distance, when the load increases and the part of the pontoon is sinking a bit deeper. What is your theory about that disbalance?
+Peter Randeler At 1:02 things are already gone out of control. The crucial question is why directly after raising of the deck, both crane tend to move. As if there is a lack of stability.
True story. I ve write on you tube the same story in Dutch. my English is not so good. I dont think you can calculete what a pontoon can do. To complicate, because speed is also a factor. It was a stupid idea, the old bridge was removed with a crane on the road. Why they don t do it like that again?
its gone with the wind . wat b the force in tons if a strong gust of wind hit that big steel sail i wonder . maybe 500sg meter sail. once it started moving b like stopping a train. 180 ton weight of bridge part
Also unlike tower or crawler cranes, the booms are solid steel with no gaps or spaces which would make the crane less aerodynamic and thus more unstable. Hopefully no one got hurt.
Great and clear analysis Peter. A contributing factor might have been that there was apparently hardly any safetymargin on the smaller crane. At the boom's lifting angle, the smaller (400 ton-liebherr) crane is rated lift no more than approx 150 ton. The bridge weight is 175 ton. Looking at the crane lay-out, the smaller crane end up lifting more than half of the bridge's weight. Experts say that the crane may have gone in an emergency mode where the operator had no control anymore and the crane computer takes over as a safetymeasure. This safety may have switched on due to the rotation of the pontoons or due to unpredictable and unequal lifting forces. The crane operator had no time to override the safety and to drop the bridge back on its original ponton. Witnesses say the operator left the crane before the bystanders were even able to see something was starting to go wrong.
There is one thing that puzzles me, and that is the sharp opposite jerk of the boat at the far end about when the bridge hits the boom of the crane. Did one of the mooring ropes break? Although the ponton was tilting, it looks unlikely that this would give a major additional stress on these ropes the way they were attached. Still there was apparently a (another) force acting on the boat...
+Alwin van Dongen I wondered also, why that boat at first is going with the pontoon and then suddenly is getting upright.
But IMHO that had no effect for the cranes themselves.
I'm guessing they didn't put the guy in charge of the operation ...in charge of the clean up.
oooo also it high in the air .maybe top of it 20 meters up it will want like a sail turn away from wind
Is there a load decrease on the left crane instead of the right? Just exaggerate that the left crane turns furher than the load rotates indeed further and further underneath the right crane which explains why the right crane starts to rotate first. Is there by the way any video evidence that the left crane indeed rotates down due to less uplift by its barge?
NIce theory, but the assumption that the excentrically loaded pontoon will lower at the side of the 700t crane is not in accordance with the footage. Further, because of the weight of ballastwater, it is not necessary that the pontoon lowers at the side of the crane. It all depends on the distribution of loads on the pontoon.
+m20anker Take a look at 1:02 - the pontoon in the front sank deeper into the water. Then they did not pump enough ballastwater into the stern, to keep the surface even.
Due to the long boom of the crane, the top of the crane will move a longer distance, when the load increases and the part of the pontoon is sinking a bit deeper.
What is your theory about that disbalance?
+Peter Randeler At 1:02 things are already gone out of control. The crucial question is why directly after raising of the deck, both crane tend to move. As if there is a lack of stability.
+m20anker That's what I mean - the ropes were'nt vertical, when the deck came free from it's supports. So it began to move immediately.
True story.
I ve write on you tube the same story in Dutch. my English is not so good.
I dont think you can calculete what a pontoon can do.
To complicate, because speed is also a factor.
It was a stupid idea, the old bridge was removed with a crane on the road.
Why they don t do it like that again?
its gone with the wind . wat b the force in tons if a strong gust of wind hit that big steel sail i wonder . maybe 500sg meter sail. once it started moving b like stopping a train. 180 ton weight of bridge part
Also unlike tower or crawler cranes, the booms are solid steel with no gaps or spaces which would make the crane less aerodynamic and thus more unstable. Hopefully no one got hurt.
eeee u can hear the wind on the recording it saying leave it and run