Saturday, December 24, 2011

December 24th, 2011

Essex England. The boom of a luffing crane suffered a structural collapse and has been left hanging while crews assemble to disassemble the structure and make the site safe. At this time, high winds are expected so the nearby flats have been evacuated. Given the fact that the crane is not likely to weather vane properly, this seems like a prudent move.

I have only found one picture on BBC's website. Link The details are sparse at this point but it seems clear that the boom is being supported by the pendant. The cause of this accident could be varied. Structural failure due to weld failures. A pin backing out at a splice connection. Side Loading. Operating in high winds. It's a wide open until more details are released.

Monday, February 21, 2011

February 20th, 2011

Stuttgart, Germany A Tower Crane collapsed inside of a 40,000 seat stadium. The crane was a mere 14 meters high, and the cab of the crane was dislodged in a way that it seapartated from the wreckage which allowed the 31 year old operator to clear himself from the cab with broken ribs. He was immediately taken to the hospital.

The crane appears to have broken away at the Cat Head to turntable connection. Sometimes these connections are made with through bolts. We have seen a number (1, 2)of Comedils come down due to poor bolting and bolts that have never been changed out after being torqued. I have personally found loose bolts on similar connections. I'm not familiar with the particular crane in use here so I can't really know what type of connection it is that we are talking about. Is it a pin that maybe had a keeper missing? A set of shouldered bolts that were not tightened due to being forgotten?

You should be putting your hands on the bolts of your cranes. I can't tell you how often I find hand loose bolts that should be tightened well beyond my physical ability to loosen them without a tool, let alone by hand. This is how we can prevent these problems from getting to the point of failure. Daily Checks should be done prior to each shift. Don't take the extra time your employer gives you to just go up in the crane and get yourself set up, walk that jib. Look at those pins. Put hands on those bolts. It's your life that we might be talking about.

Kran Unfall Stuttgart

Saturday, February 19, 2011

February 19th, 2011

Plymouth, Devon, UK A man in his 30"s fell from a tower crane. The fall was about 200 feet in length and resulted in death.
Vertikal reports the story as a man whom climbed over a security fence then climbed the crane without authorization. When he reached the turntable he found that he couldn't get any higher and then fell or jumped to his death.
The picture shows what appears to be a Liebherr 420 (US designation). These cranes have a hatch door from the turntable to cab transition. If you are the operator, you can place a lock that would prevent a person from getting past this area. The height of the cab and it's sheer sheet metal face would make it impossible to climb around without setting up ropes.
This is one of those things that we in the industry often endeavor to prevent, but it seems like a uphill battle. I've seen cranes with 10 feet of plywood walls built with razor wire at the top. The crazies still get by. People stealing copper show up to take the large power cords that feed 480v with a 200 amp service up to the crane. Operators will show up and find the cord gone. We've seen it where they've just taken bolt cutters and cut right through the live wires. I've heard a story about it happening at a crane service yard where they found drag marks  as if the person who did it was injured and couldn't walk out. Sorry, I find that hilarious. Sometimes justice moves at the speed of light.
You should do what you can to prevent people from getting themselves hurt, but if they are jumping fences, clearing plywood walls while getting through razor wire, they are determined and short of putting a couple of trained pit bulls on the second mast landing, we can't save these people from injuring themselves. Even at that, they would certainly sue here in the US for the bites that they would receive, and sadly they'd often win.

Monday, February 14, 2011

February 13th, 2011

Buenos Aires, Argentina (Palermo Las Canitas) A tower crane on a specially designed pedestal collapsed killing no one. It fell over four buildings, destroyed the ceiling of one apartment, which would have likely killed the occupants if they were in that spot, but everyone walks away from this one.

Looking at the design, I've never seen anything like it. It's a large concrete footing on top of four concrete pillars. At first my thought was that that they were trying to make it easier to finish the building at the end of the job. Normally you would pull the tower sections out, then go back and fill in the 3x3 meter holes in the floors that allowed the crane through. But if you had four concrete pillars close together like that, what could you put in that area of the building? So ease of removal couldn't have been the case. It actually looks like it would make it 100 times worse because you would have to remove all of that concrete. The only thing even remotely close to this that I've ever seen is a crane that was anchored to a large structural concrete beam that then had Aluminium Screw Jack Shoring for the next two floors down.

Looking at the base, I just don't like the way it's set up. You have a crane that is sitting on top of this large concrete block as if it's a raised footing. Then you have two floors of concrete columns. It would be one thing if the concrete portion had something to resist the torsional loading, but I don't see much that would resist that. I see some wood, but a compression or two on soft wood and you simply have wood sitting there and providing no resistance. We've all felt concrete floors move under us when a car drives by in a parking garage, and frankly a crane being loaded and torquing up to swing is doing the same thing to concrete. Since even flexible concretes are terrible in shear, what is stopping this concrete from moving? In the case of the crane on the large structural beam that I've seen, it was all tied into the floor of a building with enough mass to resist it. Here, there is little mass, and the mass that is there, only makes it worse because it's so top heavy.

For us in the field, this strongly points out the need to inspect your cranes, daily, and prior to your shift. Get out that flash light and look for concrete cracks. Don't show up to your crane and just run up the ladders. You might get the odd person whom doesn't understand. But here is the reality. That concrete, it didn't crack overnight. It was moving, and those cracks could have been seen. The same is true with most weld cracks. They spend a while moving and tearing just a bit more each time until enough of the weld has failed that it can't take the stress at all and let's go. Dig around, look. One other important thing, notice that the failure is on the side that would normally be considered loaded because the limited size of the jobsite on that side of the crane? The counterweights load that side of the crane nearly as much as the maximum pick on the jib side. So be sure to look at all sides of your crane thoroughly.

This story was brought to my attention by another blogger. Gustavo with Gruas y Tranportes (Cranes and Transports) alerted me to the story as it was in his home town. He has written a few blogs on it and there is some more information that can be found there. Thank you Gustavo.

This morning a video from inside one of the apartments came out on this website. Can you imagine the fear of watching TV while sitting on that couch! If you were under it, it might be deadly. I also found it interesting to see so clearly where the rebar was helping the concrete hold together.

Colapso de grúas en la Argentina

Wednesday, February 2, 2011

April 18th, 2009

Harbin China. A Tower Crane Collapsed due to a broken bolt, apparently in the mast of the crane. The fracture was 20 meters below the turntable. The mass of the superstructure came down killing 1 and injuring 4 others. This may be a fortunate result considering the fallen scaffolding around the building. Many more could have been on the scaffolding.

Bolt inspection is often overlooked. It's been my experience that this was an area in need of improvement when I got into the inspection side. It has greatly improved since the problems were pointed out. I'll give a couple of examples.

Markings. ASTM standards in the US require that the manufacturer and the grade of the bolt be marked and visible on the bolt. I found some bolts had no markings at all. Over the years some of the bolts would get ruined or lost. Rather than purchasing new bolts which are quite expensive, one company was making their own. I don't know of it being a problem and the machinist whom did it is quite good. The quality of the materials is claimed to be adequate, but if that bolt fails, whom is now responsible? Certainly there isn't a manufacturer to blame or pay for the damages. So I chose to have them removed in every case.

Dings in the landings and threads lessen the cross section of the bolt. This lessens the ability of the bolt to withstand the load. Personally, If I found one, or two, I might not get too excited. But if I found lots of them, I'm going to start rejecting them. These bolts should be handled with a modicum of care.

I don't believe that I have a picture of these, but I found stretch bolts to be hour glassed in the threads once. Any hour glassing is an indication of failure and internal, if not external, cracking. The bolts have been tightened to their yield and cannot be used. In this case, it stopped the crane from being erected as the section with the bolts was not able to be inspected until it arrived on site, the day of the crane erection.

A crazy one that I found was soft washers under hardened tower bolts over a large loop bolt hole. The washers were dished out and collapsed in. Even after seeing the picture, the crane owner asserted that the washers were correct. It pissed me off so I went back with a saws-all and cut a section off. A hardness test showed that it wasn't hardened at all. We eventually replaced them all. The crane in question got so hammered by me that it was never erected again. I may have to blog just about this one crane one day. It was absurd. The tower leg had even been cut into with a torch and it was just painted over as if loosing a 1/2 inch of material was no problem.

Poor Install: Washer @ Yellow Arrow Belongs where Orange Arrow is.

But back to the bolts. Bolts should be periodically NDT tested. They should be cleaned, spin freely and have oil on them when torqued. It's not something to be overlooked.

Original Harbin Story Link 

Monday, January 31, 2011

March 27th, 2010

A forum in French had this photo included. The poster claims that it's the bent lacings of an MDT 178 that bent during a load test. If you look at this post and one at the bottom of the same page, the consensus seems to be that Potain is asserting that the lacings were damaged during handling and exposed by the load test. The point being that the load test itself was not the root cause. Since this happened, Potain has shortened the flattened section in what appears to be an attempt to not have such a long flattened area that would be subject to damage from lateral impacts, or loading, during shipment.

I don't know any of these details to be factual. They do make sense and I think that they are worth talking about and noting for those operating or inspecting the flat top Potains. The jibs are tall and narrow. Given the large flattened area, looking for deformation or any markings indicating a strike in this area would seem prudent. 

Saturday, January 29, 2011

November 28th, 2008

Summerstrand South Africa (Port Elizabeth). A crane being climbed down from the Radisson Hotel was caught in the wind after it was already low enough that it was trapped next to the building. The tower is visibly being worked hard but no injuries were reported and I'm not finding any report of the crane actually coming down. Makes it a bit of a minor scare but the lesson is reportable.

Whenever you are going to climb, erect, or dismantle a crane, it's a good practice to use a reliable weather service. Here in Seattle, Weather Net has always proved reliable area by area. We have hills so and their maps and reports are great by elevation as well as general location. When we built the Narrows Bridge and were trying to get the cranes down, they were able to tell us exactly what the winds were going to be at 660 feet (200 meters) off the water and not just for the Tacoma area over the land. We had a few tight areas to get by that were so tight that we had to reconfigure the climber and it was going to take hours. All of that time was going to include an open climber which is when you are very susceptible to the winds. Find a good service wherever you are and use it. If you are going to put the crane down next to the building, you may want to know what the winds are going to do for the next two days.

If you can see that you are about to be caught, it may be a good idea to secure the crane as much as is possible. The the hook down and tie it off to something heavy at the tip that isn't going to slide. If you can rope the two jibs off to the building like you can in this case, if the wind changes direction, it can come by rather than in a case like this where you have the winds coming into that wedge between the crane and the building which is adding pressure on that tower and collar below. Since the crane can't move from there, the wedge is adding surface for that wind to strike. The height above the collar is allowing it to work that collar like a pry bar due to the leverage. The point on the jib is acting like a pivot, where as if it were tied off on both jibs, you would simply be more likely to have a jib fail ( beyond the tie off) rather than have the whole crane come down.

Having said all of that, the weather is never 100% predictable and we can all get caught. If you can't anchor the tip, get everyone safely away from the building and the crane.

Thursday, January 27, 2011

The Day that Kroll Came to Town

 NOTE: Click on pictures for a larger version

Seattle Washington. No Accident, but a notable crane was erected. A Kroll K1800 was recently purchased and built for JCM Construction. The crane is by far the largest tower crane that has been up in Seattle. In the building of one of our sports stadiums we had a Liebherr 850 up and frankly the capacity at the tip of that crane isn't half of what the Kroll is capable of. It's a monster.

JCM is a joint venture between Jay Dee, Coluccio & Michels Construction. They have partnered up to undertake a tunneling project that is set to provide underground light rail (Subway/Underground) between Capitol Hill (residential area just East of downtown Seattle) to the University District where you'll find the University of Washington. The project has been dubbed the U-Link. It's a 3.15 mile extension set to be bored by a TBM. This is much needed project here in Seattle as our freeway system was not well planned out. We lack public transportation outside of busing. This is another step that is crucial to our city moving forward. When you think of any major city in the world, it must include trains to move it's people. So besides having a giant crane that gets guys like us all excited, this is a historic moment for the city.

On to the crane story. The crane was erected by Northwest Tower Crane Service. The parts started arriving on the 6th of January. Each truck load was an over-sized load. As is typical with many large Kroll's, the jibs are inverted with the trolley running on an I-Beam. Each of the jibs were 12 feet tall which is wider than the lanes of the road. With pilot cars in the lead and tailing, the crane was brought in bit by bit from Vancouver Washington, a scant 164 miles away, and the parts arrived and were assembled on site. The process ended up taking a total of 15 8 hour days to assemble. The crane was brand new and out of the box. If you've ever assembled a brand new crane, you know how many parts we are talking about and the time to locate each bolt and washer. It's IKEA on steroids and from Hell.

After the parts were assembled and staged on site, Ness & Campbell Crane (One Company) brought in their Grove GMK 7550 outfitted with the Mega-Wing. The 550 ton crane was ran by Doug Ukert, whom runs a hook as well as one can be ran. As of the 25th, the tower was stacked and everything else was ready to go. So on the 26th, the 124,000 lb turntable, cab, and tower top were hoisted into place.

Next came the Counterjib. Weighing in at 52,000 lbs with the hoist in place, you can see that the 550 when outfitted with the Mega Wing doesn't even deflect even though the full 197' of boom is out. The process took longer than most counterjibs because of the size of the pendants. There were four connections to make instead of just two. This is no Liebherr 154 where I could move the pendants and make the pins by myself. Then two of the massive 20,000 lb counterweights were put into place. Even at this point the erectors noted that the 100 feet of tower barely flexed. A far cry from 305 feet of PECCO S35 towers with a 400 on it on loose bolts where it looks like you are at the end of long ski jump and looking back up.

To make the 250 foot long jib pick, the 550 moved away from the tower. In the meantime, the crew sent down the load line and fully reeved up the crane. The jib was lifted off of it's dunnage and towers and hoisted into place. the entire process of hanging out the turntable, counterjib, and jib took nearly 11 hours. This is with a crew that when I worked with them we had erected, reeved, and load tested a Liebherr 630 in 14 hours. It's simply a long and slow process. But when you consider that it was reeved already, it's not a bad time frame for a new crane of that size.

The crane is fully erected and only has a few more hoops to jump through. Washington State requires that all cranes are UL (Underwriters Laboratories) Listed. A private company is coming in Saturday to do that work. On Monday, the plan is to load test the crane to get it fully certified. This is where the numbers are impressive. I have to admit that I haven't seen the load chart. So these numbers are my best good faith understanding of what they are. If anyone has more accurate numbers, let me know. The operator, Willie Steinberg, hasn't sent them to me yet. But as I know them, in 6 part operation (corrected from 4 part), it's good for 66 tons (corrected from 60 tons). This will facilitate most of the TBM load out. It's still not enough for the Cutting Head which will require yet another crane. The number that really impressed me was the tip capacity. 33,000 lbs! (corrected from 32,000) Liebherr 420 or Potain 485 maximum capacities... 250 feet out.

The base of the crane is right next to the edge of the hole that will be facilitating the TBM and keeping the work going. The concrete foundation is tied back. It's also been reviewed and accepted by two Registered Professional Engineers. The hole is maintained by lagging and steel H-Beams driven into the soil. The foundation will be tested at each 45 degree position for 10 minutes with the maximum moment load. The code normally reads as at the tip, but the site will not facilitate that and the load would likely be over a live street or apartment buildings. The next best thing is to just hit the Load Moment which induces the maximum overturning moment on the foundation anyways. This test is performed with the weights next to the ground. Once stable, a measurement is taken of the clearance from the ground. After the ten minutes has passed, a second measurement is taken. If there is any deviation, then we have a soils support problem. If not, on to the next point. Normally this is done over a 90 degree arc, but since this crane foundation has been judged to be non-standard, it will be done over 360 degrees as the job allows. In this case it really can only be done over about 180 degrees. Once all of the load tests are complete and the crane is signed off by the technicians, we'll be off and running in catching up to the rest of the world by having some underground service. Many thanks to Kroll and JCM for helping us rise up as a city by providing us a tall crane so that we can go underground.

I hope to get more pictures soon. I hope that you enjoy them.

Added Load Chart on 1.28.2011

Wednesday, January 26, 2011

April 19th, 2009

Suzhou City, China During Dismantling operations a tower crane suffered a structural failure that killed 4 and injured 2.

It seems clear that the climber is on the tower near the top. The counterjib complete with weights hangs. The pendants of both jibs are connected to both the jibs and the tower top. What appears to be missing is the turntable. You can clearly see air between the tower and where the tower top is. There may be the smallest of turntables up there. If it still exists, are we looking at a turntable so thin and old that it is clearly pre-70's? Looking at the tower I don't even see any landings, nor can I make out a ladder which also makes me wonder about the age of the crane. But given the t-shaped counter-weights and the solid steel bar pendants, I would gladly let go of the age concern and assume that what we are looking at is a crane that suffered a bolt failure. Was it caused by the climber pushing into a weakened bolt or were the bolts removed prematurely? Both seem equally dubious claims, but where humans are involved, the likely cause is human err in removing the bolts, which has happened way too many times. This blog alone has it documented as happening as far back as 1985 in country after country. It never ceases to amaze me.

We have a Kroll K 1400 going up in Seattle today. I took many pictures today. The Counterjib was on, but the front jib was going to go up later in the day and I didn't want to wait around 6 hours. I'll be on the site tomorrow and get more pictures. It's a massive crane. I'll lay out the details that I can gather tomorrow, evening time here in Seattle.   

Wednesday, January 19, 2011

September 26th, 2006

Danang, Vietnam. Typhoon Xangsane made landfall in Vietnam late in the evening and made quick work of a tower crane breaking it in the mast. The crane was being used on the Hoang Anh Gia Lai Hotel project. When it snapped it came down losing it's counterweights which landed in a nearby house killing two children and seriously injuring the mother. The story is from a forum, so the details aren't confirmed. But there was a picture found to go along with the story. 

In Hurricanes or tornado's, you can't do much other than make sure that the crane is weather vaned and hope that the winds don't climb over 140 MPH or so because virtually all cranes are in trouble at that point. This particular hurricane was a category 4, which puts it at 131 to 155 mph winds. I don't think that we can fault the crane or anyone when the crane is hit with such unusual winds. Just get back from it and house people away from it. 

Tuesday, January 18, 2011

June 14th, 2010

Lyubertsy, Ukraine. A Tower Crane on a large project fell over backwards landing on a building's roof. Hopefully the building stopped the crane up high enough to prevent the operator from being killed.

The only source that I have of the accident is this video which appears to be from a cell phone. The pictures are terrible so here comes my wild speculation from what I can see. I see a jib laying on the ground in front of where I would normally expect the crane to be standing. It makes me immediately wonder if the jib structurally failed under load and caused the crane to be shock loaded backwards. Imagine being loaded heavily to the front and if the entire crane lets go, no all of the counter weight is on the back side pulling you back but you just instantly released the load on the front jib. This would cause the mast to fail at the base just as it appears to have done so in this video.

Saturday, January 15, 2011

November 26th, 2008

Kaluga, Russia (date listed is the date that the video was uploaded). A crane on rails found a support problem. It's an interesting problem. The crane was working when the underlying support under the bogies with the counterweights gave way. The crane was able to remain standing and I have every confidence that they were able to lift it and get it properly supported again. In the short term they added ecology blocks and wood under the counterweights to prevent it from sinking further.

But what was the cause? I'm actually not going to suggest that it was improper soils, but I'm not a geologist or soils engineer and I haven't seen the ground used because it is covered in snow. I'm going to suggest something else. Water combined with regular freezing and thawing can weaken soils. The water infiltrates the ground, then it freezes which causes the water to expand. As the water thaws and is able to escape,  voids are created. Much in the same way pot holes are created in roads, the freezing and thawing cycles of Russia can pose a real problem to be addressed.

The best solution in climates like this is to have a reinforced foundation under the whole of the tracks. That's a bit of a dream solution for many projects around the world. Under cranes on rails for long term installations, I would certainly recommend a complete foundation under the rails. For construction, we just won't get to that level of spending everywhere in the world. Most contractors will have the supports designed to support the rails adequately for typical scenarios and not worry about the "what if's" as much as a professional complainer like myself.

When it comes to setting up cranes, "what if" should be your motto in the planning phase. Just like construction safety in general, always know your escape route before you get into a bad spot. In this case, you should know what your weather extremes are. The most common failure in tower cranes is knowing that wind maps exist, but putting up max free standing cranes in areas with high winds. It would be more appropriate to build it a bit shorter, tie in and climb it to final height if you are exposed to high winds. The point being, consider the weather in the planning phase and you'll save money over time. Safety isn't a sprint, it's a marathon.

You can see a video of the scenario here.

поддержка Калужской кран

Thursday, January 13, 2011

January 11th, 2011

Ho Chi Minh City, Vietnam. A tower crane collapsed killing it's 24 year old crane operator. The story notes that one person on site is already blaming the height of the crane, the length of the jib, and the soft soils. One part of the picture supports him quite well.

The Original report shows a green arrow with the picture. I'm not sure what they are they are getting at. I want you to see the red arrow. It's pointing at a large concrete base up in the air. One, or multiple problems has happened. The crane base is likely too small. In relation to the size of the tower, it looks very small in width. Not that I haven't seen this before. I had a job once where the base wasn't much wider than the tower itself. but the base was connected to pilings that went 80 feet into the ground. If the base is only 4.5 to 6.5 feet deep, I'm going to suggest that it's just too small and light. The base has to resist not only overturning moment, but torsional loads. If it's small with no surface tension to adequately resist the twisting induced on the tower by the slewing of the crane, the soil will eventually become dislodged and potentially not provide adequate underlying support.

If the base is too small, it might not have enough mass to hold the crane down. The concrete base should be sufficiently large with enough safety factor that it acts as an anchor. An anchor strong enough to prevent that crane from falling over. The only way that crane should fall over is due to structural failure. Good soils on a adequately sized foundation will always cause a crane to break before it overturns. You should never see a crane foundation up like a tree root ball. And we've seen it before in Prague, again with a visibly small foundation.

Cranes are designed to match their bases. Reactionary forces are listed based on height, tower used, and jib lengths. You must match them all together and make sure that you are starting with good soil, or this may be the eventual result.

Updated photos and link

Cần cẩu sập  Việt Nam

Wednesday, January 12, 2011

October 6th, 2007

Russia. A large Self-Erecting crane went down in Russia. The building that it was working on appears to be in the process of being built. I don't see a roof and the adjacent building that is of the same type of construction is a few floors behind it. Notice that there no crane down on that building, and the roof on this one doesn't appear to be complete. Is this just another Russian crane on rails that doesn't have the shut off ramp to prevent travelling too far? Did it hit buffers or stops or just run right off a set of rails? Of course the crane is destroyed, but I can't imagine that the chances of surviving a crash like one are very good. It hit hard enough to bend up a cab simply from the shock.

I don't know the exact cause. There is a video of the news coverage linked here. I wasn't able to download the RUTube video format, so you'd have to check it out there. If you speak Russian, maybe there is more information for you in the News Story.

Русские строительного крана падает в-стрит

Tuesday, January 11, 2011

February 3rd, 2009

Malaysia A luffing Tower Crane suffered a boom collapse while lowering a load. In the report given, no injuries are reported.

The picture leaves the crane a bit distorted, but the lower crane was the Luffer. Apparently taller crane, the Hammer Head swung into the luffer while it (the Luffer) had a load on the hook. The contact caused the boom to collapse. It's not clear if the Hammer Head had a load on the hook and thought that he was clear or thought that just the hook was clear and was swinging past but the hook acted like a wrecking ball on the jib. A solid strike on a loaded boom chord with even an empty block could certainly collapse a boom.

As operators we get into a hurry. There are always pressures. The Hammer Head operator has a to be sure to be clear of the lower crane. He could certainly hoist over the lower crane, trolley out past it, or swing left rather than right. Contacts happen between very good operators. I've made contact with another crane that swung out of my area then back in with out announcing. I got myself in a hurry and I didn't double check. It's like not looking over your shoulder when changing lanes. I was relying on the radio (mirror) and not taking that half second to just look.

Another potential problem goes to job and crane planning. When using Luffers with Hammer Heads, it's important to keep the boom of the lower crane out of the air space of the Hammer Head at the slewing level. It might be difficult to plan around that, but it is a cost of having the two cranes on site. Certainly you can check the clearance on the forward jib, but with counter jib and weights hanging below the jib, there maybe little to not visibility, and even less forgiveness if you were to contact a heavily loaded crane boom.

Sunday, January 9, 2011

December 13th, 2006

Sienna, Italy. A tower crane collapsed killing the operator. The accident trapped the operator necessitating that hydraulic spreaders be used to free the operator.

The details are few and the only picture that I can find is the one included which certainly lacks clarity to help explain anything. For me, the idea of being trapped or crushed by my crane was the worst part of operating a tower crane. It would be one thing to crash due to a problem, it would be another to survive the crash only to be trapped. Maybe it's that I experience some clausterphobia when I'm squeezed and unable to move. For me, the idea of being trapped is ample motivation to inspect the crane.


Friday, January 7, 2011

May 14th, 2009

Crosio della Valle, Italy. While working on a housing project, a Self-Erecting tower crane suffered a structural failure at the base of the crane. From what I can see, it would appear that a outrigger failed while loaded directly over that leg.

The story notes fairly emphatically that that cause is structural failure. On the outriggers, the primary suspect for me is the transition from a box beam to the screw jack. You have a perpendicular structure that is welded on. Poor fusion, inclusions, ignored porosity, etc in this location are definite causes for repair. Unfortunately, any number of these problems could be buried in the weld which would make it difficult to detect outside of using Ultrasonic Testing. The only other things that would stand out to me is the need to verify that the proper counterweights were installed to resist the loading on the jib which would translate over that outrigger and that the load on the hook did not exceed the rating of the crane. This may have been one of those accidents that is not preventable using normal inspection and operating methods.

The original story linked above does have more pictures in case you were interested.

Crosio della Valle crollo della gru

Thursday, January 6, 2011

December 25th, 2007

Xi'an China a tower crane suffered what appears to be a structural failure. The mast has broken and torn just above the collar and landed on the building that it was building. The article doesn't give me good details and since I don't speak Chinese, I don't have any details as to the injuries. The crane appears to have hit the scaffolding so hopefully it was at least clear. I'm not sure if the accident occurred during a storm or during use. Since it's China, and the details are few, I'm not going to speculate any further. Link to story and video.

Wednesday, January 5, 2011

October 10th, 2010

Linz Austria. In what is being shown as a tower crane, the crane operator was thrown from the crane and died of his injuries. The story indicates that the the crane was shock loaded but gives a confusing scenario as to why or how. It could be that the translation is bad or that the reporters understanding is poor. Either way, it would appear that the operator was standing in the crane when the shock load happened and he was tossed out the window. Or at least that's my inference.

I've ran a crane that had no floor window and required that you stand when you are within 50 feet of the tower with a load. If a load was in tight, you were literally required to lean out the window in order to see. Fortunately in cases like that, you aren't likely to shock load a crane. I can see how if a operator had a window open, and they were standing, and you shock loaded a crane you could be tossed out. It fits quite nicely into my argument against old cranes. New Cranes have guards and glass at your feet and up for visibility. They have seat to sit down in. I grabbed a stuck load once that as soon as I realized it was stuck and not just heavy I stopped. I got on the radio and told my bellman and in the mean time it broke free. The load went over his head, I began hoisting up as fast as possible because it was going to be coming back down and I didn't want to hit him. Had I been standing, I could have easily been thrown. This also fits nicely into having a new crane so that you can have a functioning load cell so that you can discuss loads that don't react as you would expect them.

I'm also a fan of the idea of seat belts in cranes. So many operators live with injuries that could have been prevented by not being tossed around in the cab in collapses. I know that they'd never get used, but that doesn't mean that they aren't a good idea. As a kid I never used a seatbelt, but they were certainly a good idea. In the end, this old crane likely doesn't even have a seat and the result is a standing operator. Standing in front of a window on a tower crane that has the potential to shift unexpectedly and without warning.

Source for picture and story.
 Kran Unfall tötet Betreiber in Linz

Tuesday, January 4, 2011

September 23rd, 2008

Italy. Built on the edge of the job site, a tower crane collapsed into the home of three families destroying the home. In the two stories that I have found, neither notes anyone being injured. The cause of the accident is noted at a burst water pipe which then washed out the soils. A second story indicated that a soils engineer says that the  soil was not properly contained nor assessed.

Soils are often overlooked. Putting a crane on the edge of the hole requires that the bearing capacity be assessed. Non-native soils should also be a big red flag. Virtually every job uses a soils engineer, so what's the problem with having them assess where you are going to put the crane? Was cribbing, or matting, used to spread out the load under the pads? It's pretty straight forward that you should take advantage of spreading out the load at every opportunity. If you are putting the crane on the edge of the job site, you should consider reinforcing soils at least around the crane. Soils nails, sheet piling, lagging, air-placed concrete, CDF, etc. Find a way to slope the edge or secure the soil.

Monday, January 3, 2011

January 25th, 2009

Bern, Switzerland. A man working around a Self-Erecting Tower Crane was killed when it "slipped" off to the side. He was killed in the accident.

The information shown doesn't give any clear indications as to potential causes. There is only on brief moment in the news story that seems to show the crane with out riggers folded out as if it were sitting on the outriggers. It's clear that there is considerable snow in the area. As a point of consideration in these scenarios, if you are going to set up over snow, you'll want a shovel. You should not be setting up metal outriggers on snow or even frozen ground. It's important to use wood in these cases. The reason it's important is not for compression, but rather torsion. A metal outrigger on frozen ground will have little resistance to slipping if the ground is not level, or sliding if the crane is slewed. There are torsional resistance requirements on cranes. It's rare that this becomes a problem, but this is a case where it may have been a concern that should have been heeded. So at the time of year when Europe and North America are covered in the white stuff, make sure you take the extra 5 minutes to remove the snow whether it's on a Tower Crane on pads or a Mobile. Do this both under the pads and or under the matting used.

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