Wednesday, July 14, 2010

October 30th, 2008

Changwon South Korea, A tower crane suffered a wild collapse. The Outer Jib and Counter Jib both collapsed and were effectively hanging by their pendants. 1 was noted as killed and 3 were reported as injured.

The cause of the accident isn't clear in the report. From the translation it would appear that testing was occurring on the crane. I don't see any gap between the turntable and the mast so I don't imagine that it was climbing. I've certainly felt oscillation in climbers before that felt very bad for the crane. Bouncing bad enough to cause the pendants to slacken up. But since there doesn't appear to be a gap there, I wouldn't expect that to be the cause.

Was a keeper missing from a pin at the outer to inner jib connection? That could be violent enough to cause the counter jib to buckle. Was there a structural defect? The joints on the lower chords are welded on. It's a weld that is often ground down so smooth that it isn't visible. Most of the lower chord pins are under compression, most of the time. The joint adjacent to queens posts would have considerable shear added due to the down force of the pendants carrying the load. Certainly a weld is normally acceptable there, but what if there was a defect in that weld? It's a spot that we should be looking at during the pre-erection inspection.

타워 크레인 붕괴

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