CN Tower: Concrete Telecommunications & Observation Tower

Structural Classification & Design

The CN Tower is a concrete telecommunications and observation tower—not a habitable building. At 553.3 m (1,815 ft), it was the world's tallest free-standing structure (1976–2007) and remains the tallest in the Western Hemisphere.

Structural System

• Core: Hexagonal concrete shaft (0.9 m thick at base, tapering to 0.3 m)
• Legs: Three curved concrete "legs" forming a Y-shape, post-tensioned
• Radial Trusses: Steel, connecting core to legs at intervals
• Foundation: 6.7 m deep, 22 m diameter, massive concrete raft
• Antennas: 102 m steel mast atop concrete pod

Strength Features

• Designed for 418 km/h (260 mph) winds (Category 5 hurricane)
• Seismic resistance to 8.5 Richter
• Sways up to 1.5 m at top in extreme winds
• Height-to-width ratio 11:1—extremely slender
• Post-tensioned concrete handles tension; massive compression capacity

Functions

TV/FM/Cellular broadcasting, tourism (observation decks, EdgeWalk, revolving restaurant), lightning research, iconic landmark.