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

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