The boom of an All Terrain crane buckled while lifting a rooftop cooling unit onto an office building in Provo, Utah yesterday.
The boom buckled at the base
The crane, a 220 ton Grove GMK5275 (GMK 5220) owned by Arizona based Wagstaff Crane, was working with the second and third section retracted and all smaller sections extended. The buckling occurred at the base of section four. The crane, which has a seven section 68 meter main boom, was operating with the boom at a fairly low angle, possibly around 30 degrees.
If the rest of the boom was fully extended the crane would have been working at a radius of around 44 to 46 meters. The crane appears to have two counterweight sections installed – around 21 tons – if so the boom is limited to just under 50 meters and maximum radius 44 meters, depending on how much boom is out and capacity is in the region of 2.2 tons. Although the outriggers are short rigged so it may be lower.
A close up of the buckled boom
The crane’s swing-away extension has dropped from its stowage brackets on the side of the boom, suggesting some sort of impact or impact. One report said that the crane tipped and then settled back onto its outriggers. If so it is possible that the buckling was caused by a dynamic shock load.