Structural and blast engineering for vertical “top hat” addition to embassy office building with stringent security requirements. 205,000 sf.

Weidlinger Associates provided structural design and blast engineering services for the design of a top hat addition to an abandoned embassy building to create a new 10-story, 205,000-square-foot US embassy complex in Moscow. Construction on the original eight-story building was nearly complete in 1985, when it was discovered that foreign workers had installed electronic listening devices throughout the building. The structure was subsequently abandoned and operations continued in the overcrowded former apartment building that had housed the embassy's offices since 1953. Dubbed “Operation Top Hat,” the new four-story vertical addition, a steel structure built without the use of foreign workers or materials, was constructed atop the foundation, columns, and first six floors of the previous building, now used for unclassified diplomatic business.

The red brick facade and walls that formed the original shell were removed and replaced with a white limestone facade and sweeping curved glass curtainwall that overlooks the Russian parliament. A vertical recess above the main entry reveals a distinctly different inner skin. The complications of designing a new structure to be placed atop an existing building were compounded by stringent Department of State site security, blast resistance, and progressive collapse requirements. Weidlinger succeeded in meeting the requirements without altering the original architectural concept.

Completion Date: 2000
Location: Moscow, Russian Federation
Owner or Client: Department of State, OBO
Prime Consultant(s): Hellmuth Obata & Kassabaum (HOK)