Saturday, October 23, 2010

July 17th 2009

Bellach Switzerland. I got some updated information about a self-erecting tower crane that went over. The internet was kind enough to send me some pictures that really show the story. In the original story I was concerned about the ground and support under the crane. It turns out that was exactly it.

Rather than building up the ground and compacting then using matting, they chose to span over a void to sit on a pre cast concrete vault or man hole. Who made this decision? I find it hard to believe that they could move over 5 feet or even just rotate the base to avoid the void. Sometimes we get focused on doing something one way and we fail to see options. In this case it was to the crane's demise. Was it a $100,000 mistake? I often see self-erectors on buildings. Frankly, if no one were to provide me a engneer"s drawing, I'm out. In this case, I would have required that the void be filled in and substantial matting be implemented. You can't reliably rely on pre-cast with unknown reinforcement.

You have to see one more photo in here too. Not only did they come up with their own bridge design, but they used inferior materials. Look at the quality of this wood at the break. It's split along it's length due to age and at the fracture you can see the dry rot. There were other pieces where the dry rot was clearly evident where there were no fractures. If you are going off the script for what would be sound practices, at least use sound materials. 

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