How the Willis Tower Was Built — And Why It Sways 6 Feet

The Willis Tower became the world's tallest building using a revolutionary design that structural engineers called "su1c1de" - nine hollow tubes bundled together like drinking straws, creating a 110-story structure with no interior support columns. The technique terrified experts because it had never been tested above 40 stories.

Fazlur Rahman Khan's "bundled tube" theory defied everything engineers knew about skyscraper construction, eliminating the traditional steel skeleton for a completely hollow interior. The building was designed to sway up to 6 feet in Chicago's notorious winds, causing motion sickness among occupants who could feel the structure flexing during storms.

Despite predictions of catastrophic failure, the building not only survived but revolutionized tall building design worldwide. Khan's techniques enabled every supertall building constructed since, from the Burj Khalifa to modern mega-towers. The Willis Tower proved that sometimes engineering breakthroughs require accepting risks that seem impossible.

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