Freedom Tower: A Building as a Symbol for Freedom

Context

Immediately after the events of 9/11, DYWIDAG was involved in stabilization measures at Ground Zero. In 2001 and 2002, the DYWIDAG supplied a wide range of high-quality strand anchors from its factory in Toughkenamon, Pennsylvania, which were used to stabilise the excavation.

Construction of the Freedom Tower began on 27 April 2006, based on plans prepared by Daniel Libeskind and David Childs. Due to the impact of 9/11 on New York, the tower carried a symbolic significance that extended far beyond the city.

The planned height of 1,776 feet (541.32 m) reflected the year of the American Declaration of Independence, reinforcing the building’s symbolic meaning. The tower was intended to become a clear sign of resilience against terrorism, with a spire illuminated at night to reflect the Statue of Liberty’s torch.

Solution

The design placed strong emphasis on security. The structure was built on a nearly 60 m deep foundation using a steel–titanium compound designed to withstand extreme forces, including explosions. The walls were constructed with approximately 90 cm thick reinforced concrete combined with steel armour. Critical infrastructure such as elevators, staircases, and utility shafts were positioned within the building core to maximise protection in the event of structural damage.

The tower houses approximately 250,000 m² of usable space and is limited to 69 floors for security reasons. The outer structure was erected using a steel frame method, while the elevator shafts were constructed using reinforced concrete and climbing formwork techniques.

Due to the structural design, significant forces acted on the elevator shafts. As a result, a large horizontal girder measuring 35.0 × 5.0 × 2.0 m was installed approximately 30 m above ground level. DYWIDAG supplied Bar Tendons for this critical structural element. The 65 mm Bar Tendons were installed in nine layers, each consisting of two tendons.

In addition to these tendons, 96 #20 DYWIDAG bars were installed for horizontal reinforcement, and 168 #20 bars were installed for vertical reinforcement within the girder, contributing to the stability and strength of the structure.