Live and Dead Loads on the Eiffel Tower: Engineering Analysis

The Eiffel Tower (324 m, 7,300 tonnes puddled iron) is engineered to withstand a complex combination of permanent and variable loads:

Dead Loads (Permanent, Static)

• Self-Weight: **~7,300 tonnes** (iron structure). Distributed non-uniformly: massive lattice base (4 legs, 125 m spread) tapering to unified column. Foundation pressure ~4.5 kg/cm² — remarkably low.
• Non-Structural Elements: Paint (60 tonnes, reapplied 19x), elevators (hydraulic → electric), restaurants (58 Tour Eiffel, Jules Verne), antennas (TV, radio, 5G — added 24 m height in 2022), lightning protection.

Live Loads (Variable, Dynamic)

• Visitor Loads: **Max 5,000 people** simultaneously (2,500 per level historically). Dynamic crowd loading → vibration serviceability checks. Current limit: ~3,000 for comfort/safety.
• Wind Loads (Dominant Lateral): Designed for **2,500 Pa (2.5 kN/m²)** at top — equivalent to **~200 km/h (125 mph)** gust. Lattice geometry **reduces drag 80%** vs solid surface. Sway at summit: **≤ 15 cm** (designed).
• Thermal Expansion: Iron expands **~15 cm** height increase on hot summer day (ΔT ~40°C). Base pins allow radial expansion; structure "breathes."
• Snow/Ice Loads: Wet snow accumulation on platforms/lattice. Designed for **~100 kg/m²** on horizontal surfaces. Asymmetric shedding → dynamic imbalance.
• Seismic Loads: Paris = low seismicity (Zone 2/3). Designed for **PGA ~0.1–0.15g**. Lattice ductility provides resilience.
• Maintenance Loads: Cranes, gondolas, scaffolding, abseiling teams — temporary but heavy. Strict load plans.
• Elevator Dynamic Loads: 5 lifts (2 double-deck to 2nd floor, 2 to summit, 1 service). Inertial forces during acceleration/emergency stop.

Load Combinations (Eurocode / CM66 Legacy)

Ultimate Limit State (ULS): 1.35G + 1.5Q_wind + 1.5Q_thermal + ...
Serviceability (SLS): Sway < H/500 (324m/500 = 65 cm) — actual < 15 cm.

Eiffel's genius: **Wind permeability + material efficiency** → minimal dead load, maximal wind transparency. The tower's weight (7,300 t) is less than the **air displaced** (7,800 t) — it would float if sealed!