Looking at the overhead picture, it's not clear as to why the cross base failed. Did it have a structural failure? Did the ground give way? The ballast is present and the crane was not working at the time of failure so I'll assume that it wasn't a lack of ballast. One thing that I have experienced on a cross base is the ballast attempting to "walk" on the beams. If the ballast is not secured in place somehow, minor flexing in the horizontal beams can move the weights. you would think that it would be impossible, but it happens. Some of the older cranes don't have methods to lock the weights in place, and these are the ones that we really need to be aware of. Most late model cranes have recesses to prevent this walking of weights. If you had a crane that didn't have this, I'd want to mark the weights on the beams and strap them in place just for that warm and fuzzy feeling and as a best practice.
No one seems to track tower crane accidents world wide. Annually we see 30 plus major accidents world wide with around 50 deaths. It's a dangerous game and we all need to be vigilant in the construction world.
Friday, July 9, 2010
April 26th, 2002
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