Construction on the New NY Bridge project has entered an exciting new phase with the installation of pile caps and the first vertical steel sections of the new span’s piers starting to rise above the Hudson River.
The team’s focus for the past year has been on installing the pilings below the river to form the strong base needed for the Tappan Zee replacement. Now approximately 60% of the pilings are in place and the giant steel tubes are being cleaned out. Once that happens, 300-ton pre-cast concrete “pile caps” are slowly lowered into place and serve as foundation platforms for the bridge’s approach span piers. Dozens of the approach span pile caps will be built and installed between now and the end of the year.
The pile caps—the size of tennis courts—are prefabricated at an offsite facility and resemble concrete tubs with holes at the bottom. Following a thorough inspection, the caps are moved onto barges and transported to the project site.
The project’s reinforcing steel, all sourced here in the United States, is specifically engineered to ensure that it can be precisely formed and positioned. In order to protect the steel, it is also coated with a corrosion-resistant layer of zinc through a process called galvanization.
Next, the piles and tubs are fitted with a labyrinth of these steel-reinforcing bars, or rebar. The tightly-hewn network of rebar is then enclosed with up to 750 cubic yards of concrete, from the project’s floating batch plants. The resulting composite material, steel-reinforced concrete, combines the strengths of both materials.
The end product: incredibly strong foundations that will support the new bridge well into the next century.
Once the pile caps are in place and inspected, vertical steel rebar cage columns begin to rise overhead. The first of these can now be seen rising about 40 feet above one of the pile caps at Pier 39 near the Tarrytown shoreline.
To learn more check out the “Bridge Rising” video at NewNYBridge.com.
Brian Conybeare is the Special Advisor for the Tappan Zee (New NY Bridge) Project