Deck construction on the New NY Bridge which will replace the Tappan Zee Bridge in the USA is currently under way with the I Lift NY super crane lifting 125m-long sections of steel and a derrick crane installing hundreds of road deck panels to form the base driving surface of the bridge. The stiff-leg derrick crane uses a system of guy wires, winches, counterweights and a mast to raise materials, and incorporates some modern technology in its hoisting system, which can raise up to 80t at once. The derrick’s real strength is its ability to quickly perform without the need for complex hydraulics and electronics, making it energy-efficient and a perfect fit for jobs that require frequent lifts into a single area over an extended period of time – such as the project’s road deck operations, particularly on the Westchester approach.
This area of the bridge is located more than 30m above the Hudson River – beyond the reach of most project cranes. However, the derrick operates atop a 45m-tall blue tower on a mobile barge. The combination of this perch and a 40m lifting arm allows the derrick to easily reach both of the bridge’s spans on the Westchester approach. Its mobile barge also allows the project team to move the machine to new areas as road deck construction continues.
The road deck consists of nearly 6,000 interlocking concrete panels that are prepared offsite and barged directly to the derrick. After the panels are properly rigged to the derrick’s lifting arm, an operator takes control of the machine from water level. Signal crews, standing at the roadway level, communicate with the operator via radio as the panels are hoisted to their final position. After the panels are safely placed atop the bridge’s structural steel girders, they are connected into a single base surface with steel reinforcement and concrete. The derrick will continue placing road deck panels on the Westchester approach throughout the year. By next year, it will be moved to the Rockland approach to assist with the bridge’s westbound span.
