Protective Design - World Trade Center Towers

Overview

Protective Design & Security provided blast resistant design services for the World Trade Center Towers 1 (also known as the Freedom Tower) through 4. We worked closely with the developer, security consultant, project design team and state and city officials to establish the appropriate level of protection required for these buildings and determine the associated operational security measures.

Highlights

• We performed high-fidelity finite element analyses of the primary structural elements of each building to determine their responses to extreme blast loading. Our team used the results to determine the most cost-effective combination of blast-hardening upgrades that satisfied the design criteria. We also performed similar finite element analyses of the façades to determine curtain wall design requirements.
• In addition to integrating new safety designs, the building has expansive open public spaces, which needed to be designed without columns. This was achieved by 15-story tall vierendeel trusses. A nine-story glass winter garden leads to a three-story lobby and atrium that is 90-foot column-free span. In addition, a tuned liquid-column mass damper — a 300,000-gallon reservoir of water — is installed at the top of the building to increase the comfort of the building occupants by limiting its wind induced accelerations.
• The structure achieved LEED Gold Certification under the LEED Core and Shell Pilot Program by the US Green Building Council and uses 40% less water than characteristic office buildings of this size.