Grade 8 Reading Comprehension Worksheet

Why Bridges Sway

When engineers design a bridge, one of their biggest challenges isn't just supporting weight — it's managing motion. Wind, traffic, and even the footsteps of pedestrians create vibrations that travel through a bridge's structure. If a bridge were built to be perfectly rigid, these vibrations would have nowhere to go, and the stress could eventually cause cracks or structural failure. Instead, many modern bridges are engineered to sway slightly, allowing built-in flexibility to absorb and dissipate energy safely. This is why some suspension bridges visibly move in strong winds — that motion isn't a design flaw, but a deliberate safety feature. Engineers calculate exactly how much flexibility a bridge needs so it can bend without breaking, similar to how a tree's branches bend in a storm rather than snapping.