Page 364 - Forensic Structural Engineering Handbook

TEMPORARY STRUCTURES IN CONSTRUCTION 10.51

The following description of the incident is from the July 14, 2004, four-page memo-
randum by OSHA, Investigation Report of the February 17, 2004 Fatal Crane Incident at
Sikorsky Bridge, Stratford, CT
The incident occurred on February 17, 2004, at approximately 12:00 PM. The contractor
decided to employ two cranes, each mounted on a barge, to hoist the north girder [in Span 8]
after removing the bridge deck, stringers and floor beams. The contractor removed the metal
deck and stringers. But before the floor beams could be cut from their connections to the north
girder, the girder was rigged to the two cranes. The American crane had applied a lifting force
of 70,000 pounds at the east [cantilever] end of the girder, while the Manitowoc crane applied
a force of 68,000 pounds at the west end [over Pier7]. At this moment, the girder was still par-
tially supported and seated on the piers in Span 8. The contractor then cut the remaining four
floor beams from the north girder and the cranes were ready to perform tandem lifting.
According to the interview statements, the last floor beam was cut near the west end of the
girder. Both cranes were directed to lift the load. The Manitowoc crane was directed to lift the
load slightly. However, before the Manitowoc crane operator could lift the load, the operator
of the American crane had already lifted the east [cantilever] end of the girder between 6 in to
2 ft above the pier cap. The girder reportedly oscillated in the north-south direction and then
buckled at a point near the east [cantilever] end. The boom of the American crane buckled and
failed, dragging the crane off the barge and plunging the crane into the river. The crane oper-
ator was killed. The west end of the Manitowoc crane tilted up 4 to 5 feet from the barge.
Fearing that the crane could overturn, the Manitowoc crane operator immediately released the
load. The load dropped and the boom snapped backwards overtop of the crane.

The OSHA memorandum did not include illustrations.
A similar description and additional details of the incident are in the illegibly-dated untitled
seven-page accident investigation supplementary narrative report of the State of Connecticut
Department of Public Safety. Of particular interest are the following two paragraphs:

Prior to the accident which occurred on February 17, 2004, [the contractor] had a demolition
crew remove the necessary steel grid deck, stringers and some of the floor beams in prepara-
tion to removing the north girder of span 8. On the morning of February 17, 2004, two cranes
were employed to lift the 192 foot long north girder. An American 931 OA crawler crane
equipped with 180 feet of lattice boom was positioned on a barge by the east [cantilever] end
of the north girder. This American 931 OA was rigged to the north girder by a shackle and a
20 foot endless sling approximately 10 feet, 6 inches from the east [cantilever] end. A
Manitowoc 4100 W crawler crane equipped with 200 feet of lattice boom was positioned on a
barge by the west end [over Pier 7] of the girder by a shackle and a 20 foot endless sling about
3 feet in from the west end of the girder. Both cranes were equipped with a load cell which
enabled each operator to know the load or force that he was applying to an accuracy of plus or
minus 1 percent as stated by the manufacturer.
With both cranes rigged to the 192 foot long girder, a lifting force of 70,000 pounds
was applied by the American crane positioned on the east [cantilever] end of the girder,
while the Manitowoc crane applied a lifting force of 68,000 pounds at the west end [over
Pier 7]. At this point in time, both cranes were just securing the girder so that the demoli-
tion crew could complete the remaining cuts on the four floor beams. With this force
applied by each of the cranes, the girder was still resting on its bearing seat. Iron workers
of the demolition crew had severed the last floor beam which was attached by the west end
of the north girder [over Pier 7]. The iron worker who made the last cut on the floor beam
maintained radio communication with the crew (which included both crane operators).
Upon finishing his last cut he made his way to a safe location and instructed the
Manitowoc crane to “cable up” (to lift). However, this ironworker noted that the American
crane [at the cantilever end], not the Manitowoc crane [over Pier 7], had lifted the girder
by the east [cantilever] end off its seat or pier cap. It appears that the operator of the
American crane [at the cantilever end] acted on the ironworker’s command meant for the
operator of the Manitowoc crane at [Pier 7].