Swaying Bridge

Crossing this new bridge is a thrill! The world’s longest pedestrian bridge recently opened in Arouca (ah-roh-ka), Portugal. The 516 Arouca bridge is 516 meters (1,693 feet) long and stretches over a river valley.

The 516 Arouca is a suspension bridge. It has towers on each side of the valley that hold up two strong ropes, each made of seven metal cables. Thinner cables connect these ropes to the deck, or footpath, where people walk. The weight of the bridge puts tension, a stretching force, on the cables. Many big bridges are suspension bridges. It’s one of the best types of bridges for long distances. 

As people cross, the bridge swings under their feet. That’s actually part of the design, says Paul Endres, an architect at the Illinois Institute of Technology. As the wind and foot traffic push on the bridge, a slight sway keeps the forces balanced. But architects and engineers design suspension bridges not to sway too much so they are comfortable for people to use.