http://www.nbcnews.com/news/world/least-107-dead-crane-collapse-meccas-grand-mosque-n425891 RIYADH, Saudi Arabia — A towering construction crane toppled over on Friday during a violent rainstorm in the Saudi city of Mecca, Islam's holiest site, crashing into the Grand Mosque and killing at least 107 people ahead of the start of the annual hajj pilgrimage later this month. There is a video there, too.
Oddly enough, it happened on the anniversary of 9/11, celebrated by the attendees. ``The construction giant Saudi Binladin Group is leading the mosque expansion and also built the Abraj al-Bait project. The Binladin family has been close to the ruling Al Saud family for decades and oversees major building projects around the country. The Binladin family disowned one of its many members, late al Qaeda leader Osama bin Laden, in the 1990s.''
And just because I'm an "An ounce of prevention is worth a pound of cure" kind of guy, and I can see an enormous potential for a lot of us to want to somehow connect the dots in a political or religious fashion, I'll just post this simple reminder of the forum rules:
Hell of a storm. Not much information but it looked to me like maybe they had the crane tied off to a load or an anchor point, and when lightning hit it, it parted the hoist line? She went straight back over, her tracks are standing straight up. If it wasn't tied down, I would call that criminal negligence.
What I find odd is that the boom was facing the wind as it went over backwards. The tower cranes we have used for a number of years specify to be not tied off. They are to be stowed with the block pulled up and trolleyed in close to the tower and the machine left with the swing brakes off allowing them to windvane. The last ones I used on a project had a automatic warning system that started beeping at 25 MPH and sounded a long warning horn at 30 MPH wind to give you time to set the load down and unhook. After 3 minutes of steady horn it was designed to put itself in windvane mode to save itself. The wind force on the side of a 250 ft boom is huge. That being said many of our U.S. cranes that do not meet current safety rules here go to other countries for use. The specs on all the newer big Manitowoc cranes are to not tie them off either but to also let then windmill when out of service. I'm not sure if the one in the picture was a true tower crane or a T-series crawler with a tower boom on it but it should have had the long end of the boom facing straight downwind if it was properly stowed. That being said if the storm was violent enough anything could happen. EDIT: At first I thought the upturned tracks were another crane that got caught up in the mess. After watching the video again a few times it appears that perhaps the boom was facing down wind. The luffing jib threw me off. It appears to be just a big crawler with luffer, not a tower crane at all. It appears that it went over the same as if it was overloaded. Wonder what the wind was measured at.
Well done " nuff said"
Please accept my apologies if my post gave a whiff of political opinion. My mind was focused solely on crane safety and the tragedy that, in insurance language, appears to be an "act of God".
No apology necessary. As I said, an ounce of prevention is worth a pound of cure. I recognize that the events of 9/11 still generate strong feelings for many of us, myself included. On the other hand, I also recognize that the rules have served the forum well, and that while a discussion of this accident in terms of the nuts and bolts aspect is consistent with our mission, venturing into political or religious speculations is not.
I'm going to guess 60+ on the wind. From the look of the way she went over and what I could see of the crane laying on her back, the operator almost surely set the house lock with the boom over the front of the tracks.
Even on the ground, people seemed barely able to stand up.
The little bit of video I saw presented a lot of questions in my mind. I saw the back boom and luffer and then another photo that showed the house and carbody. It appeared the angle of the main boom was way low at the start of the video and the question in my mind was with the main boom that low, where was the wheel horse and back weights. I can't imagine a wind by itself being strong enough to blow over a big crawler. I'm sure there is a large human element in this. In any case is a mess that will likely take years to sort out.
This is supposed to be how the crane was configured https://www.washingtonpost.com/worl...c7e0-590b-11e5-abe9-27d53f250b11_graphic.html
With the boom just about straight up and only the weight of the luffer over the front , wouldn't take all that much wind on a couple hundred feet of boom surface to start it moving backwards, and of course once the main boom went past center it was all over. John C., I don't see what you're saying about the boom angle? Only video I saw that showed it still up, it was already past center and falling backwards?
I apologize for the misstatement on the boom angle. I only saw one piece of video on television and didn't look carefully even at that. The boom might have already been in motion at the starting point of what I saw and it appeared to be a single boom going forward. Now that I think about it I didn't see the queen posts, so going over backwards makes sense. That makes the accident even stranger in my mind. There is not much surface area in a lattice boom and a luffer is usually laid out far enough forward that there is plenty of weight over the front of the house. So for wind to push this over backwards means there was some extremely bad luck or serious human error.
Judging from comments in the media a sudden electrical storm with high winds, loads of blown sand, and torrential rain literally came out of nowhere. With the length of boom and luffer on that crane I can see how if it was facing the wind just right it would whip everything over backwards literally in the blink of an eye.
The Binladen group state that all was in order. Shaikh Ahmad Al Gamdi, former head of Makkah’s religious police, told AFP the accident was a “test” from God. Case closed? (info from Gulfnews.com)
I was thinking that the crane was not being used. It would seem very odd that they would be hoisting while the area was jam packed with the public. Normally a luffer setup like shown in the post above would have the luffing jib folder over at least parallel to the ground and often folded almost all the way down. The main would normally be lowered to 60 degrees or so also. I think lantraxco got it right and the house lock was on. A "parked" rig shound be in free wind condition. Maybe so many cranes as close as they were did not allow for proper stowing.
I'm not an expert on those wheeled counterweights shown in the Washington Post article linked by KOR in Post # 12 on Page 1. Do they permit the upper frame of the machine to weathervane in high winds with the swing brake off..? I would have thought there would be too much friction between the wheels and the ground, especially with the main boom almost vertical and the luffer also pretty well up the weight would be biased well to the rear.
I'm not sure how all manufactures accomplish it but I watched Manitowoc test the 21,000 series a number of times during development in 1999 or 2000. ( I lived across the road at the time) Watching them pick 500 tons with 580 ft of boom including luffer, the load would start to lift, the wheels would lift off the ground a ft or so and it always appeared to be balanced when swinging with the wheels off the ground. The wheels were always on the ground when swing with an empty hook. I was to far away to see all the details but I did see the wheels turn 90 degrees and be facing the counterweight a few times. I believe they moved the maxxer counterweight in or out to balance. I am not sure of any changes that may have been made on the production machines. They tipped a luffer and boom over backwards onto the cab once also while working out the erection sequence. No injuries fortunately. As they reported publicly thats why they test in a controlled envirionment.
I've seen them work as old-iron-habit says. Most of the ones I've familiar with used the wheel horse to pick up the boom and luffer and then just left it sitting behind the machine on the wheels or taken it off completely. When a max lift was performed the wheel horse was picked off the ground by the machine for the lift and then set back down when the lift was completed. I don't know about it being moved in relation to the center point of the machine but with today's technology I wouldn't doubt it. I have also seen them parked with the luffer in a storage position pointing nearly down or at least parallel to the ground and the boom angle down some. I've also seen the area under the potential fall area cordoned off. At any rate by the sounds of it, we will never really know what happened .
There is much discussion of the event here: http://www.skyscrapercity.com/showthread.php?t=1437182&page=299 If you look at the photos and evidence presented, it would appear to me that the crane was secured facing away from the building as the work done with it was completed, at least the phase to be done prior to the Haaj, which starts soon. I believe the failure was leaving the boom and luffer at too high of an angle, and the hook was free in the air. IOf the hook was tied off to the ground or even the base of the machine, it may have prevented the boom from going over, but I do not know the proper procedure for securing a crane like this. I am guessing, but from the look of the fences and barriers at the site, the boom may have been left high because it appears the area directly below it was fenced off. If the boom was lower, the fenced area may have needed to be larger, and it seems they were maximizing space for the visitors. Again, this is speculation based on the pictures I have seen. It also seems the storm came in quickly and was much more intense than what was expected. I must say that I am surprised that the graphic in post 12 above is a relatively accurate depiction of the crane as it was sitting, with the exception of the superlift weights not being attached, not that they would have changed the outcome. . That is rare accuracy for any piece of equipment from a mainstream news organization. Despite any differences is beliefs, it is a sad day to hear about a tragedy such as this.
I don't believe any Transi-lift types of any manufacture can weathervane. As you posit, there is just too much work (in the Newtonian sense) in spinning the counterweight around without power.
If you watch the cell phone video of the crane boom going over, you can see several other crane booms behind it in similar configuration, all basically aligned in the same direction. Somebody's idea of a salute perhaps. With thunderstorms and microbursts, I'm not sure even a tower would have time to weathervane fast enough to take the side load off the boom and column, inertia is a bitch and sometimes those winds blow in circles.
The crane that collapsed was a massive crane. You can compare it to the nearby and adjacent tower luffings, which are very big. The boom on the crawler was very much long and deeper.
And a conventional horizontally configured tower has a much greater weathervane moment than a steeply configured crane. There isn't enough leverage on almost any crane with a steep boomangle to weathervane well (or at all).
It appears to me in the first picture I seen that all the other cranes were facing in the opposite direction of the one that went over backwards.The boom of the fallen crane was then pointed in the direction of the other booms. When stowed the boom of the luffer should be level or tilted downward. If the boom was deliberately left that straight up wither the house was locked or not to minimize space requirements, a tragic error was made.
Todays Duluth News Tribune had a short article that stated that the construction company that owned the crane had not erected it properly and that the board members of the construction company were forbidden by the king to travel or leave the country. Stay tuned to see how the justice system works in this one.
I fear there may be more deaths from this accident, executions are still popular there.
That makes sense. I have not run a luffing jib and I don't really want to. So I honestly don't know the manufacturer recommended boom angle to leave it unattended safely. All the ones I've seen, at the end of the day the operator would boom down the main and the jib so that the head of the jib was almost touching the ground. (Or maybe was touching? I don't remember) I am thinking perhaps the high boom angle is how the wind had enough leverage on the boom to push the boom over backward.
The lower the boom angle, the more weathervane forces the crane must resist, and it seems certain that trans cranes can't swing without power. The steeper the boom angle, the higher the chance the boom can topple backwards. As Bucket pointed out, a steep main boom with a very lowered luffing jib would be the best solution.
The wind had a whole lot of help.
Yea that one Saudi guys said that, "the hand of God" so to speak (God's will is what he said and they really believe that for the most part). Yea with them not letting anyone who may be involved it's not a good situation for them. But if they did do something negligent that resulted in 107 dead plus some injured they need to answer for that. Rick
If this company which is reported to be one of Saudi's largest construction company is like most companies, the upper management would have no clue if the crane was properly erected or stowed.
Even more so in the oil rich Arab countries, usually all the real work is done by contract labor from Europe or North America, or at least that's what I've heard. Management position are usually handed out based on bloodline rather than ability and experience.
If I can remember right the same thing happened in NY city about 2 years ago. A tower crane was set with the boom angle set to high and house was locked and could not weathervane. A fast storm came up blew the boom back over. Can't remember any other details. Does any body else???
Other than a Link Belt model that was popular in the 70s tower cranes typiclly to not have a boom that is adjustable up and down. The tower that fell that I remember in New York or somewhere near there a couple of years happened when they dropped the jacking section during a lifting operation. It tore off the guy wires on the way down resulting in the crane going over backwards killing the jacking crew and the operator and damaged to a few other building. I don't believe any one not envolved with the lift got injured or killed.
I don't think that's true today, especially not in Europe anyway. Back in the day everything was fixed boom on tower cranes, today everything seems to be luffing booms on pretty much every construction site I walk past.
You are seeing lufing booms on tower cranes in Europe? I have only seen luffing jibs on large crawler cranes that seem to be poplar on sites today here in the U.S. Tower cranes have remained the traditional hammerhead style.
I would say that well over 50% of the tower cranes I've seen over the past year or so are luffing jibs. TBH it surprised me as well, as I was brought up on the more "traditional" fixed boom style. Maybe the issue is that with urban construction sites becoming more and more restricted space-wise regarding the buildings that surround them then possibly a fixed boom won't work in a lot of cases because you need to boom up to get past certain fixed obstructions then boom down again to reach other parts of the job site. Here's a link to one product line from Liebherr. All the other major manufacturers seem to offer something similar. http://www.liebherr.com/CC/en-GB/region-UK/products_cc.wfw/id-12545-0/measure-metric
You're not thinking of the one in Hurricane Sandy, are you? HeavyEquipmentForums
It's happened in UK also. Safety directive issued by the UK's equivalent of OSHA regarding placing the boom at the correct angle and releasing the swing brake to allow the crane to weathervane in high winds. http://www.hse.gov.uk/safetybulletins/luffing-jib-tower-cranes.htm
The evening news showed video of a tower crane (not a fixed boom) with a 60' lattice boom blow over backwards. After Googleing it, it was from Sandy Oct 2012.
Thanks for that link Nige. They look like the Link Belt we used at Basin Electric power plant in North Dakota in the late 70s. The Link Belt had a sliding counterweight on it that moved in and out about 12 ft. I wonder why they call it a luffer? They appear to have a normal boom configuration with standard gantry and pennant lines. I have not seen any of them in this side of the pond. I can see where one could get by with a shorter tower and if other obstruction exist it could be boomed up to clear instead of having to go higher like a conventual tower crane.
I don't remember this one at all. I was on a 12 hr, 7 day week project for 6 months during which time Sandy hit. That tower still standing shows just how tough they really are. The last tower job I did we had 2 Potains and they were set up to automatically go into weathervane after a warning horn blew for a couple of minutes to allow time to drop the load and unhook.With 260 feet of front boom and a 90 ft tail on a 280 ft tower we were limited to 20 MPH for hoisting and it was supposed to go into auto weathervane at 30 MPH. The operator would get alarms in the cab at a 25 MPH wind. We never tested the auto part as we always had plenty of time to shut down when the wind come up.
Try this. Go into Google images and simply put enter "london tower cranes". I'd say that well over 50% of the images are luffing jib cranes.
Read an article once about a tower operator, talked about how there were times the wind would come up while he was operating and he couldn't get out of the cab, had to ride the weathervane all night until the storm passed. Maybe newer units you can exit while they're turning?
IIRC, the crane was set to weathervane, but a strap or something hanging from the ball got caught so the crane couldn't swing.
Way back in my US Navy days a luffing pic involved two lifts at one time. There was the straight pick and then another set of tackle that would pull the load away from the straight line pick which enabled increasing the radius of movement without an increase in boom radius. Inside a ship there are pad eyes all over the place above where machinery is mounted. We used block and tackle to move that machinery from eye to eye all the time. Large crawler cranes with a luffing boom allow reaching over something and then moving the load horizontally. Say you want to set an air conditioner unit in the middle of a building and you can't get an angle that would allow a single boom to reach the spot . Use a luffer and now two boom angles are available. I always thought a jib boom could fill that purpose and I guess they do but all the jibs I've seen only carry a fraction of the load that a true luffer could do. Jibs also only pick the small loads at high speed straight up and down. At any rate when you look at the graphic loaded early in this thread you can see how complicated those giant crawler machines really are. I have seen tower cranes with a regular crane boom installed instead of the hammerhead. Plenty of shipyards and seaports use them. I don't know if that would be considered a luffing boom though.