Crane collapse in NYC 1

[TehMightyEngineer]

[URL unfurl="true"]http://gawker.com/a-huge-crane-just-fell-down-in-lower-manhattan-1757291101[/url]

At least one fatality so far, definitely going to be a high profile case.

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[BUGGAR]

You have to lower the boom to counteract the counterweight. There is a "sweet spot" here. A crane is designed to be overloaded by it's counterweight and the load lifted balances everything out and gets the load up. You have to lower the boom just right the right amount to help balance the "dead load" of the counterweight so it is as stable as you can make it. And miss any nearby lawyer schools.

 

[BUGGAR]

I should have mentioned that this is general crane stuff and may not apply to this accident.

 

[itsmoked]

oldestguy, I would expect the whole thing to be assembled off of a bunch of flatbed trucks. Still doesn't answer my question though, how could they ever lower it without completely clearing the blocks and blocks and blocks it would cover?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Hi Keith I agree that it is unwise to allow anyone under the working area of a crane.

Workers were in the process of lowering and securing the 565-feet-tall crane this morning before it was toppled over by 25 mph winds. "The crew was directing people away from Worth St. as the crane was being lowered," according to de Blasio.

I'm thinking that the jib should have been luffed or lowered first. There appears to be a large wheel or wheels at the end of the jib.
These are common on large cranes of this type.
As these cranes are errected, the main boom is lifted first and the end of the jib is allowed to roll along the ground. When the main boom is near vertical, the jib may then be safely raised.
I susspect that they did not intend to lower the crane all the way to the ground.
They may have been intending to only lower it enough that there was no danger of the wind blowing it over backwards, as in Mecca.
That would explain lowering it with the jib in the working position.
A combination of ice build-up, the extended jib and gusting wind may have moved the center of gravity out past the end of the tracks.
Once the crane starts to fall, the radius of the boom CG increases and continues to increase and the radius of the CG of the crawler part complete with counter weights decreases and continues to decrease. From that point, there is no going back.

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

 

[bridgebuster]

Surprisingly not much coverage in the local press about the accident. There was more interest about the city council voting itself a $36K pay raise. If I didn't read the posts here I probably wouldn't have realized my first engineering job was in the building to the left of the wreck; back then it wasn't called Tribeca.

 

[itsmoked]

Thanks Bill. Your theory holds water for me at least.

Keith Cress
kcress -

http://www.flaminsystems.com