New NY Bridge Project: New Bridge Towers Rising
Courtesy of New NY Bridge Project
Tappan Zee Constructors, LLC has begun creating the new bridge’s iconic 419-foot main span towers by utilizing self-climbing concrete jump forms which, along with climbing tower cranes and catwalks, will allow crews to assemble the rebar (steel reinforced) cages and pour concrete into the towers in segments, staring from the bridge’s foundations and slowly working up to the towers’ full height.
See it on the New NY Bridge website or here:
Four towers will be built on each of the two main spans pile caps (eight towers each) with the individual jump forms atop the approximately 25-by-26 foot base (650 square feet).
As crews complete segments of each tower, the jump forms are raised through a screw jack system to move higher into the air so the next segment can be built upon the one under it. Each of the eight towers require 26 lifts from 12 to 18 feet high and will follow the outward angle of the towers, and their decreasing areas, as they rise higher.
When they’re more than two-thirds complete, cable anchorages will be installed.
As the towers rise, temporary vertical and horizontal catwalks will extend to connect them so crews can easily access them along with stairs and temporary elevators.
An internal and external frame system comprises the forms: the external form moves with the crew as it installs steel reinforcements, and the internal form remains with the previous segment of the tower, until the reinforcing steel is installed, and the new segment is ready to be filled with concrete, acting as a casting mold to form the shape of the towers as the concrete cures.
Once complete, a series of rails raises to the next level with the external frame, and the process begins anew.
Crew members’ safety is ensured by fall protection lines around the external frame. TZC personnel trained for this process by created a full-size tower base mock-up offsite in July 2015 to prepare them.