Four super high-rise buildings have been planned for the World Trade Center site, with the first officially opened building named Two Ford. This tower is not only stable and highly functional but also features a distinctive facade that adds vibrancy to its surroundings. Located along Cortlandt Street, this skyscraper rises 977 feet with 72 floors, constructed at a cost of $120 million.
The building offers a total above-ground area of 2.3 million square feet, including 1.9 million square feet dedicated to office space. Floors 15 through 54 follow a parallelogram floor plan, each spanning 44,000 square feet. From the 57th to the 72nd floors, the layout shifts to trapezoidal shapes oriented towards Manhattan’s southern corner. Standing on these floors, visitors’ eyes naturally drift towards the nearby 9/11 Memorial and Museum, a solemn attraction.
One of the primary architectural objectives was to maximize visibility from office floors while ensuring the corners remain column-free. To achieve this, the design team implemented a steel-concrete composite shear wall structural system. This approach optimizes space efficiency and meets stringent building requirements.
On the west, north, and south sides of the office areas, the distance between the inner core and the outer wall measures 45 feet, while on the east side it is 35 feet. The corner areas are column-free thanks to cantilevered steel beams extending between 20 and 45 feet. Along each floor, the outer steel beams span 80 feet between columns. This innovative design expands the architectural perspective and subdivides each floor into six separate office or conference areas, compared to the traditional four.
Additionally, the presence of four frame columns on each side creates a direct and clear vertical load path, eliminating the need for multiple transfer columns and thus avoiding unnecessary costs.
Use of trusses in horizontal structural systems
Steel staircase installation
Different floor levels
Innovative Shear Wall Construction
Traditionally, shear walls are constructed starting with the core walls. However, the general contractor recommended using a composite shear wall system embedded with steel ribs and beams. Structural engineer LERA adopted this advanced design.
The use of steel-concrete composite columns in the outer frame simplifies steel beam construction while offering several advantages:
- Connection nodes between steel beams and frame columns can be placed outside the column’s boundary or at the inflection points of the outer frame beams. This allows for partial bending connections where bending moments are zero, instead of conventional fully rigid connections.
- Strategic splicing points keep steel beam segments under New York City’s truck transport weight limits, improving transport and crane lifting efficiency.
- Locating outer frame steel beams at floor slab edges eliminates the need for costly and time-consuming temporary supports during concrete pumping.
- Coordination with curtain wall installers, concrete pumping teams, and other contractors is streamlined, enhancing installation speed and safety.
This thoughtful design reduces nearly 75% of additional nodes typically required by subcontractors, lowering costs.
Large-span steel beams achieve necessary stiffness using rolled steel sections of model W36. Stiffeners are welded at maximum bending moment points, with reinforcing plates staggered at beam joints. These improvements, based on traditional steel structure techniques, significantly reduce the cost of cantilevered and large-span beams between frame columns.
Core Tube Construction
The structural core tube houses elevators, staircases, restrooms, and equipment rooms. It consists of two independent tubes connected by steel beams, with the central corridor situated between them. Typically, connecting beams attach directly to columns embedded in the shear walls, requiring strong bending resistance at these nodes.
For this project, structural engineer LERA proposed relocating the columns within the shear walls away from the wall surfaces. Although this increases steel beam material costs slightly, it substantially reduces node connection expenses, resulting in overall cost efficiency.
On the equipment floor, where floor loads increase significantly, a full-height perimeter belt truss was designed to carry the loads transmitted by the outer frame steel beams, which span 80 feet with 45-foot cantilevers. The chord members of the belt truss are made of W14 wide flange H-shaped steel rotated 90 degrees. This arrangement facilitates direct load transfer from chord members to main truss nodes while avoiding the need for large node plates.
Additionally, the construction site occupies a limited area accessible only via the church and Liberty Avenue. The ground was specially designed to withstand heavy truck loads to support construction activities.
The 4 World Trade Center Tower is the first super tall building to rise at the World Trade Center site, utilizing nearly 24,000 tons of steel. To this day, it remains a prominent landmark in the area.
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