Wanderlust World Wanderlust World Large metal bridges expand and contract significantly with temperature changes. Without expansion gaps (joints), the results are catastrophic:
As temperature rises, steel expands (≈12 µm/m/°C). A 1 km bridge lengthens ~12 cm over a 10°C rise. Without gaps, compressive stress builds until the deck buckles laterally or crushes supports.
As temperature falls, the bridge shortens. Without gaps, tensile stress pulls the structure apart, cracking welds, fracturing bolts, or rupturing members.
Wind induces oscillation. Expansion joints dampen movement; without them, resonance can amplify sway, leading to fatigue failure or collapse (as in the Tacoma Narrows Bridge, though its failure was aeroelastic flutter).
Gaps (typically 25–100 mm) are filled with compressible seals (neoprene, silicone, metal fingers) allowing movement while keeping water/debris out. They are engineered for the bridge's expected thermal range, seismic activity, and traffic loads.
Expansion gaps are not optional—they are fundamental to the structural integrity of every long-span metal bridge.