How Do Bridges Support Weight?

Every bridge must transfer loads (its own weight, vehicles, wind, earthquakes) from the deck to the foundations and ultimately into the ground. The five main bridge types use different strategies: Beam bridges (the simplest) resist loads through bending — the top surface compresses and the bottom stretches. Arch bridges channel loads outward and downward along the curve into abutments, using compression throughout (stone and concrete are strong in compression). Truss bridges use triangular frameworks of connected members, distributing loads through tension and compression in different members. Suspension bridges hang the deck from cables draped between towers; the cables carry tension while the towers carry compression, allowing spans exceeding 2 km. Cable-stayed bridges use cables running directly from towers to the deck. The Akashi Kaikyo Bridge in Japan (1,991-metre main span) is the longest suspension bridge, while the Danyang-Kunshan Grand Bridge in China (164.8 km total) is the longest bridge overall.