Case Study: Blackstone Group & EQ Office transform Willis Tower with Thornton Tomasetti

Blackstone Group & EQ Office transforms Willis Tower with Thornton Tomasetti’s 470,000 ft² repositioning

The customer, Blackstone Group & EQ Office, faced the challenge of significantly expanding the retail and tourist experience at the base of the iconic 108-story Willis Tower without adding new foundations and while the building remained fully operational. Thornton Tomasetti provided integrated structural engineering, façade engineering, construction engineering and protective design services to realize this complex repositioning.

Thornton Tomasetti's solution involved designing a system of 72 transfer columns and 80 transfer girders to distribute the new podium's load onto the existing, irregular caisson foundations, requiring no new footings. The team also strengthened existing columns, rehabilitated building components, and engineered a complex gridshell skylight. This successful renovation added 300,000 square feet of new retail and entertainment space and created a new public rooftop garden, significantly modernizing the half-century-old landmark.

Blackstone Group & EQ Office