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Crane collapse in NYC

Crane collapse in NYC

RE: Crane collapse in NYC

(OP)
Wonder if the snow had anything to do with it? Can slipping of the outriggers occur if you have a poor coefficient of friction under them?

Professional and Structural Engineer (ME, NH)
American Concrete Industries
www.americanconcrete.com

RE: Crane collapse in NYC

Quote (TME)

Can slipping of the outriggers occur ...

The subject crane is a crawler crane - there are no outriggers.

RE: Crane collapse in NYC

Video of the collapse from the 30th floor of an adjacent building:
http://www.nytimes.com/2016/02/06/nyregion/crane-c...

Gothamist appears to be actively updating as information comes in:
http://gothamist.com/2016/02/05/crane_collapse_tri...

Quote (Gothamist article)

None of the victims were workers connected to the crane, which is owned by the Bay Crane company. Four buildings were damaged, including New York Law School on West Broadway. The crane's fall impacted gas mains, and officials say there are gas leaks in the area. Several buildings have been evacuated, but none of them were residential.
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.
The crane was inspected by the Buildings Department yesterday because the company had requested permission to extend it to its current 565 feet height. There are some 376 of this type of crane, called a "crawler crane," in use throughout the NYC, and de Blasio has ordered all of them to be lowered and secured in the wake of today's incident. 76 taller "tower cranes" have also been ordered secured.
The crane operator is being interviewed by the NYPD, but it's currently unclear if any criminality is suspected.

RE: Crane collapse in NYC

Seems to me the operator kept the boom mainly in the roadway, minimizing the damage to the four buildings. It also appeared to happen very slowly...

As it was snowing, I wonder if icing could have been a factor, increasing the wind force and overturning ice load?...

This could have been a lot worse...

Mike McCann, PE, SE (WA)


RE: Crane collapse in NYC

Quote (msquared48)

I wonder if icing could have been a factor, increasing the wind force and overturning ice load?...

Very likely. Lattice boom members have a lot of surface where ice can accumulate. Puts the ice's weight in the worst place for overturning.

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

RE: Crane collapse in NYC

More modern cranes also have load-indicating instrumentation, so I would think they would be aware of any icing and its effect.

With the wind at a certain nominal speed, it could be channeled down through the buildings at a higher speed.

RE: Crane collapse in NYC

Does it look like the boom has a sag in it? I've never seen/been around a crane that large and was wondering if that was normal.

RE: Crane collapse in NYC

BridgeEI - There is a distinct angle in the boom where the "luffing jib" meets the main boom. That is intentional.

I believe the crane is a Liebherr LR 1300...

News reports state the crane is rated 330 tons, the boom length in use is 565 ft. Those numbers are an exact match for the Liebherr LR 1300.

The company that owns the crane, Bay Crane, has at least four of this model: Link

The photo above is a "spitting image" of this model:



Based on the specs for the Liebherr LR1300 (see link below), handling 565 ft. of boom, the absolute maximum allowed, would be a real challenge even under ideal condition, which was not the case this morning.

Liebherr LR1300 Specifications

www.SlideRuleEra.net idea
www.VacuumTubeEra.net r2d2

RE: Crane collapse in NYC

Am I mistaken, but does this seem to be happening more often?

RE: Crane collapse in NYC

Strikingly similar to the dale in Mecca. These cranes are great, but rely on having a load or being tied down. Once they get close to vertical you loose all control and high winds will basically blow it backwards and there's nothing to stop it once it starts.

www.eng-tips.com/viewthread.cfm?qid=394730

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Crane collapse in NYC

But in this case wasn't the boom being lowered and then took off down? Seems like a mechanical failing like a brake couldn't hold it. The relatively slow descent looked sort of like a slipping brake (that keening sound) that couldn't hold but did slow the boom until the crawler tipped. Once the crawler started over the brake could actually hold since the torque load suddenly reduced.

I'm amazed the driver wasn't squished.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Crane collapse in NYC

Sorry, i want able to view the video until now. Looks like a failure or error in the lowering procedure and maybe the extra weight of any snow or ice made the difference. The fact the base unit turned over tells you the brakes were working but clearly not enough counter weight to stop the decent

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Crane collapse in NYC

He damaged the New York Law School.

RE: Crane collapse in NYC

I'm not understanding what they mean by "lowering it". Were they really going to put it on the ground? All 600 feet of it? How could they do that without a completely cleared street? Or do they mean just lowing it to 5 stories or something?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Crane collapse in NYC

It was wet snow yesterday morning in NYC; didn't accumulate on the ground.

RE: Crane collapse in NYC

Mr. smoked: How do you supposed they assembled it and then got it up there? Lowering is done in reverse.

RE: Crane collapse in NYC

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.

RE: Crane collapse in NYC

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

RE: Crane collapse in NYC

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

RE: Crane collapse in NYC

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

Quote (News Report)

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

RE: Crane collapse in NYC

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.

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