| by Janie Rosman |
Another page of bridge history took place last week when the I Lift NY fitted a 600-ton precast concrete pile cap on a set of piles. It was the super crane’s first of many placements and future lifts.
“You have this tub that is sitting over four piles that are accepting the load, so precision is key,” explained Prof. Ted Zoli, HNTB National Bridge Chief Engineer on the bridge project.
Strong winds and choppy waters were no match for the crane’s precision and zero margin for error.
“You’re surveying it, and you want to hold the tub vertically so you’re not changing the position of the load,” Zoli said. Having cleared around the piles, the arm began lowering the tub carefully, slowly, within that allotted clearance.
The piles are supported on four adjustable beams “….that will support the pile cap once the crane lets go,” Zoli said. The cap will be lowered into position, and each beam will be wound down to the top of each pile to support the pile cap on them. “Once contact is made, and the load is taken off the crane, the four beams are used to continuously lower the pile cap to its final precise place.”
Tubs will then be filled with rebar and concrete. Perched on a 384-foot barge, the lifter was anchored by spuds, which are like parking brakes, plunged 60 to 70 feet into mud (depending upon floor elevation). With neither a steering system nor self-propulsion, it was moved and positioned by tugboats, and then maneuvered by anchors running out 600 feet from the sides once the spuds were pulled up. The crane’s power comes from three diesel-powered main generators and one auxiliary generator incorporated into the barge.
“We brought in the I Lift NY super crane to reduce construction time and cost, and this first lift is another symbol that the New NY Bridge is officially on the way,” said Thruway Acting Executive Director Robert L. Megna.
Following a six-week journey from Oakland, CA, days before Christmas 2014, escorted by tugboats Lauren Foss and Iver Foss, the super crane arrived at The Port of New York and New Jersey. It was sent to a private facility in Jersey City where it was prepped and did test lifting before traveling to the project site.
Owned by bridge builder Tappan Zee Constructors, LLC (TZC), it sits high in the water, reducing the project’s dredging needs by 50 percent.
The crane’s lifting power (1700 metric tons or 1929 U.S. tons) will hoist and place sections, some weighing 900 to 1,000 tons, of the new twin-span bridge and will assist when the current bridge is dismantled.