On March 15, a 200-ft (61m) Favelle Favco 440 tower crane collapsed after it had been climbed. Riggers were attaching a collar on the upper part of the crane’s mast to tie it into the building. The collar slipped, and knocked out two collars that were tied below. Without any connections to the building, the crane toppled on top of nearby buildings on 50th Street.
OSHA wants to replicate the exact site conditions. It has specified the contractor to rig one tower section with four polyester slings choked around a leg of the tower, inclined diagonally by 40 degrees. OSHA will supply the tower and the slings.
OSHA has tendered for the load on the slings to gradually increase until they destroyed.
According to the tender, the tower section weighs approximately 11,500 lbs (5t). The slings’ ultimate capacity in tension (gravity direction) is approximately 20,000 pounds.
The contractor is to replicate the test three times and produce a written analysis with photographs and video. Testing and results are to be kept confidential.
The tender closes 21 July, and is expected to be awarded the same day. The final report is due August 27.
