What is a cable-stayed bridge?
A cable-stayed bridge is a bridge whose deck is supported by inclined, tensioned cables, the stays, that run directly from the deck to one or more tall masts called pylons. The stays carry the weight of the deck and the traffic to the pylon, and the pylon transfers those forces down to the foundation.
How it works
Each stay is a tension member. Because the stays are inclined, they pull the deck not only upwards but also towards the pylon. As a result the deck is in compression along its length, while the pylon mainly carries compression. Unlike a classic suspension bridge, a cable-stayed bridge does not need massive anchor blocks on the banks.
Cable-stayed or suspension bridge?
- Cable-stayed bridge: the stays run in straight lines from the pylon to the deck.
- Suspension bridge: two continuous main cables hang in a curve between the towers and are anchored at both ends. The deck hangs from those main cables on vertical hangers.
Cable layouts
- Fan: all stays meet at or just below the top of the pylon.
- Harp: the stays run parallel and are attached to the pylon at different heights.
- One or two planes: the stays are anchored along the centre of the deck or along both edges.
A well-known Dutch example is the Erasmus Bridge in Rotterdam (1996), a cable-stayed bridge with a distinctive angled pylon.
Application
- Medium to long spans over rivers and harbours.
- Footbridges and cycle bridges, where the stays also add architectural character.
- Sites where there is little room for intermediate piers in the water.
Tips and points of attention
- Design is specialist work: wind, cable vibration and fatigue drive the design. Always have it calculated by a structural engineer.
- Maintenance: stays, anchorages and corrosion protection need regular inspection. Water at the anchorages is a known weak spot.
- Small scale: even for a cable-stayed garden footbridge, the cable forces must be taken down through a sturdy mast and foundation.
Related terms
- Pylon
- Suspension bridge
- Arch bridge
- Chain bridge
- Cantilever bridge
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