十万个为什么·科学启蒙30篇（2）

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为什么桥梁不会在重载车流下坍塌？

Engineers carefully calculate how much weight a bridge can safely hold.
They use strong materials like steel and reinforced concrete to handle heavy loads.
The shape of the bridge—such as arches or suspension cables—helps spread force evenly.
Wind, temperature changes, and even earthquakes are tested in computer models before building.
Regular inspections check for tiny cracks or rust that could grow over time.
Expansion joints allow bridges to safely shrink or stretch with temperature shifts.
Each part of the structure shares the load so no single point bears too much stress.
Modern sensors now monitor vibrations and strain in real time during rush hour.
Even a small design error could cause failure, so safety margins are always built in.
That’s why well-designed bridges can last over a hundred years without collapsing.