Polyester straps blamed for breaking and spurring a deadly crane collapse held fast during an experiment designed to simulate the disaster, a videotape shows.
The experiment, arranged by defense lawyers and shown Tuesday at crane rigger William Rapetti's manslaughter trial, is meant to counter the heart of the allegations against him: That the crane fell because he took safety shortcuts in using the straps to secure a nearly 6-ton steel collar around the towering rig in March 2008.
Rapetti, 49, didn't take steps to protect the straps against fraying, deployed only four when the manufacturer recommended eight and used one strap that was badly worn, prosecutors say. Under their theory, the worn strap failed, quickly overloading and breaking the remaining straps. That unleashed the steel collar and destabilized the crane, according to prosecutors.
The nearly 200-foot-tall rig toppled onto a block near the United Nations, killing seven people, hurting two dozen others and leaving a swath of destruction.
Defense lawyers say the crane was undermined by engineering decisions and questionable welding — not Rapetti's use of the straps, which they say followed normal industry practices.
The experiment, they say, shows the straps wouldn't have ruptured the way prosecutors envision.
The test was conducted in recent months with pieces of the actual crane and the same kinds of straps, one also used, said Leo Y. Lee, an engineer hired by Rapetti's lawyers.
When the worn strap was cut, the other three held, with one corner of the collar dropping about 8 inches, the video showed.
One of the straps — known as slings — did tear partially during the roughly 15-minute experiment, the video showed.
Still, Lee said, the test indicated that "under the most adverse condition, when we cut (the worn strap) ... the other three slings would have picked up the load."
He suggested the crane collapsed because of cracks and other problems in metal beams that tethered the rig to the building under construction. Under his theory, one of the beams failed, rocking and ultimately tipping the crane. The straps ultimately tore because the crane was falling — not the other way around, he suggests.
The engineer who designed the crane, Peter Stroh, acknowledged in testimony last week that the beams weren't made to his specifications, but he said he ordered them fixed.
Lee said the welded repairs — meant to reinforce crucial pinholes used to attach the tethering beams to the crane — weren't adequate.
Prosecutors were likely to respond while questioning Lee later Tuesday.