Sunday, April 26, 2009

April 26th, 2009


The initial reports on the cause of the Taipei accident is overload and weather. The crane was rated for 3.2 tons at the working radius and the load picked was 4 tons. Additionally it was windy during the lift. Wind loading is all too often neglected. The most common number for maximum wind loads on tower cranes is 70 kph or 42 mph. You need to heed the manual in the crane. Pressure to make picks has killed before, it will kill again, just don't let it be on your crane. The most famous case of wind overloading is the Big Blue Crash at Miller Park in Milwauke that killed 4 Ironworkers.
Why is it that this crane didn't have it's load limits set as well? I always thought that was the beauty of being a tower crane operator. The crane can make the pick or it can't, period. There is no turning of the key and puching the limits into your safety factors.

In Singapore the collapsed luffer has been safely dismantled. A 800 and 600 ton crane was brought in and operated for 22 hours to get the crane down. Anyone who has been involved with a fallen tower crane can tell you that it's a delicate operation to dismantle it. Pick points are not what you would always hope and you are torching metal apart and uncertain of weights. I don't envy that work and applaud their ability to get the crane safely apart in mid air.

The openess of the recent accidents is refreshing and helps us all as good reminders to use proper and prudent practices.

Friday, April 24, 2009

April 24th, 2009

Taipei, Taiwan At approximately 1:40 in the afternoon the boom of a crane on the 37th floor broke away from it's mounting and "went to the street". It landed on a passing tourist bus killing 2 or 3 people depending on what report that you read. The picutre doesn't show much in terms of the crane, so it's hard to have any idea of what's happened as of yet. The boom is square and without apparent catwalks, so it's even possible that it's a derrick boom. I'll post it here until I hear anything else differnet . As a Note, Taipei lost two luffing tower cranes back in April of 2002 due to an earthquake during the construction of Taipei 101. Those cranes came down from the 56th floor and killed 5. The link to the video of that accident can be found by searching Taipei on the blog. Additionally, this is the 5th major tower crane accident worldwide in the last month.

Another view

Thursday, April 23, 2009

April 23rd, 2009

Admore Park, Singapore Potain Luffing tower crane has suffered a structural failure at 30 stories. The accident happened at 11:20 pm due to high winds. Luffers are partifularlly suceptable to failures in the winds. Depending on the length of boom, the boom angle needed to allow for proper weather vaning at night is critical. If the winds start and hit the boom dead on and surge it would be possible to blow it over backwards. If the swing braes were not opened or dragging too hard then the same thing could happen, the boom gets blown over backwards. About eight years ago there was a story locally of high winds coming up during a dismantle of a old Pecco 280. The counterjibs were solid diamond plate 6 plus feet wide sitting in I beams. To dismantle the counterjib you hoist up the counterjib to maybe 15 degrees from the horizontal. Winds started coming in hard and fast and hitting 70 mph while they were elevated. The counterjib started lifting off of the mobile cranes rigging and changing from loose to tight to loose. The mobile crane was now ending up over capacity at times and so the decision was made to put the jib back together and in a horizontal condition rather than taking the chance to collapse the mobile crane too. The point, winds can be fierce and they must be respected. Wind loads grow exponentially on structures so mind the boom angles and if you are on a luffer with the brakes dragging, remember this accident they go through the blog. It's all too common.  

Monday, April 20, 2009

April 20th, 2009

Bellevue Washington. The November 2006 crane collapse caused the death of Matthew Ammon. I was a crane erector on that crane. I/we complained of the problem that led to the collapse of that crane and have been subsequently deposed. I was set to give testimony in the Ammon Trial. Matthew's family had sued two companies involved with the crane, the general contractor, Lease Crutcher Lewis, and the engineering firm that designed the steel base for the crane, Magnusson Klementic. During the crane erection we noted movements in the base of the crane exceeding normal acceptable tolerances. We stopped, huddled at the base of the crane, got the measurements, informed the general contractor of the problem, calls were made then we were told to proceed, this had been planned for. 
Reality... Tower Cranes must be erected to a deviation of plumb not greater than 1 inch of deviation for every 40 feet (more accurately 1:500). The same is true for the horizontal plane. Normally when we set a base we allow an 1/8th inch of deviation in the 8 foot span which will keep us well within tolerance. The deviation that day was 1 inch in the 8 foot span. That equates to >5:500 which is well beyond nationally accepted design standards established in ASME B30.3 2004. The crane base was deflecting to this deviation over and over depending on the moment load of the crane at any given time. Metal Fatigue set in and the crane eventually ripped one of the beams it was mounted to. The design or the execution of it was effed up from the begining as I had stated during the crane erection. 
Attorney's and the system that we have doesn't ferret out any better truth than we had the following day. No one has earned more by hiring attorney's with the possible exceptions of MKA and LCL. It's too bad that we live in a system where it takes 2.5 years for obvious truth to be owned up to. I hope that the Ammon Family finds peace and they know that we have improved as an industry. I will see to it that we continue to improve nationwide as well.  

Saturday, April 11, 2009

April 10th, 2009

Manama Bahrain A crane collapsed that appears to be some form of a tower crane. You have a base that is knee braced, a upper rotating super structure, a platform on a jib section, and triangular jib. One article states that 3 were injured with no deaths. The accident occurred during testing, but the next sentence is that the crane is capable of 35 tons so it could not have been an overloading accident. Information is missing and the next article that I found was in Arabic. If anyone has anything to add, please feel free to do so.

انهيار رافعة برجية

Friday, April 10, 2009

April 2, 2009

Qingdao City, China Tower crane collapsed last week that I am just now catching. The article is light on content. The picture on the top with the platforms is a climbing section. I don't know that it was being used but the number of the dead suggest that it may have been in use. One operator and four guys on the climber would be very common. The top tie in is demolished as well which does make me ask why? Most climbing accidents happen due to a bad move by the guys climbing the crane. Is it possible that we have a structural failure on the tie in say at the building? Of course I don't know, it's just a question. The tower having broken right at the collar could suggest there there were no internal braces used. The collars put a tremendous amount of stress on the tower, squeezing it and creating a fulcrum point. Most manufacturers use braces internally to resist those forces by pushing back out.
Interesting pictures with a total lack of information. China news... Crane parts fell.... 5 dead... Qingdao City China.