Towering at 975 feet, Tower 4 will be the fourth tallest skyscraper on the new World Trade Center site. Designed with two distinctly shaped floor plates, the 63-story tower will be home to retail space on the first five floors and office space on the remaining 56 levels. For the lower- and mid-rise sections—floors 7 to 46—the floor plates are in the shape of a parallelogram, echoing the configuration of the site. The high-rise section, floors 48 to 63, will feature a trapezoidal floor plate. According to the architect, Fumihiko Maki, Maki & Associates, Tokyo, Japan, “The fundamental approach to the design is twofold—a minimalist tower that achieves an appropriate presence, quiet but with dignity, becoming a tribute to the Memorial, and a podium that becomes a catalyst in activating and enlivening the immediate urban environment as part of the revitalization of downtown New York.”
The design of the tower poses many challenges for the concrete contractor, Roger and Sons Concrete Inc., Lagrangeville, N.Y., however, those challenges are being met by formwork supplier, Doka USA Ltd., Little Ferry, N.J.
The formwork supplier combined the efforts of two of its departments: the Self-Climbing (SKE) Department that will work on the tower’s 90x90-foot main core, and the Shoring Department, which is involved with the design aspect of the slab formwork. To climb the inside of the main core as well as the concrete mega-columns, the SKE department is using a combination of SKE 100 climbing system and Xclimb 60 formwork. The modular climbing system offers flexible positioning, automatic climbers as a single-section climbing scaffold, and lift heights of 18 feet. The formwork, designed for safety in small- to mid-sized climbing applications, will be used on portions of the project that require vertical transport on each level.
The contractors chose to hand set the outside formwork under the slabs. The building has four structural concrete levels belowgrade with slabs up to 36 inches thick and columns up to 7 feet in diameter and 6x6 feet square. “We also are using preassembled tables for the structural concrete slab belowgrade,” says Mike Schermerhorn, Doka’s senior account manager for Tower 4. Structural steel framing the building at street level will take place six to eight stories above the pouring of the concrete core and the mega-columns. A series of material-loading platforms will be used to move materials inside the structure and a table lifting system for the exterior.
The Shoring Department designed a combination of tables, shoring and formwork for the concrete slabs and beams. Meeting the different shoring heights, often reaching 24 feet high, is solved by combining the tables with prop extensions and table frames.
The concrete work is scheduled for 2011, and the completion is slated for 2012. According to the Alliance for Downtown New York, “In just a few years, Downtown will become a showcase for the latest innovations in architecture, design, and urban planning. When all of these momentous projects are fully realized in 2012, they will stand as magnificent symbols of renewal.” Doka USA Ltd. 877-365-2872. www.dokausa.com.