A lift bridge is a movable bridge whose deck stays horizontal and is raised vertically as a whole. Towers stand on either side; between these towers the complete deck moves straight up, creating more clearance beneath the bridge for shipping.
How it works
- Lift towers — two towers carry the lifting mechanism
- Counterweights — large weights in the towers keep the deck balanced, so little force is needed to raise it
- Cables and sheaves — the deck hangs from cables running over sheaves at the top of the towers
- Drive — motors raise and lower the deck
Because the deck stays horizontal, a lift bridge is suitable for rail and road traffic across large spans.
Application
- Shipping routes — where tall vessels must pass but a fixed high bridge is undesirable
- Railway bridges — the horizontal deck is favourable for train traffic
- A well-known Dutch example is the De Hef railway bridge over the Koningshaven in Rotterdam
Points to watch
- Limited clearance — unlike a bascule or drawbridge, there is always a maximum height (the raised position of the deck)
- Waiting time — raising and lowering takes time, which affects road and shipping traffic
Related terms
- Bridge
- Bascule bridge
- Drawbridge
- Swing bridge
- Structure
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