What is a rolling bridge?
A rolling bridge is a movable bridge that does not lift but rolls horizontally aside: the deck sits on steel wheels running over rails on the abutment. To open, the whole deck is drawn back until the navigation channel is clear. It is therefore a relative of the retractable or thrust bridge, and an alternative to the bascule and swing bridge.
Advantages and drawbacks
Advantages
- Simple construction with few moving parts and no heavy counterweights carried aloft.
- No restriction on air draught when open: the deck is entirely out of the way.
- A low silhouette; in open country or a historic townscape the bridge is barely noticeable.
- Unaffected by wind during operation, unlike a high-lifting leaf.
Drawbacks
- As much clear space is needed behind the abutment as the bridge is long — in a built-up area that space rarely exists.
- The weight to be moved grows quickly with span, so the application is usually limited to footbridges and cycle bridges.
- Rails, rollers and the recess the deck slides into must be kept clear of debris, leaves and ice.
Related forms
- Unrolling bridge — a bridge that unfolds or uncurls like a ribbon or a pair of scissors until it reaches the far side. Best known from a handful of striking footbridge designs.
- Rolling bascule — here the leaf rolls back along a curved rolling surface over a rack, so the deck tilts and rolls rearward at the same time. That needs less counterweight than a conventional bascule.
Rolling bridge as lifting gear
In sheds, workshops and factories “rolling bridge” means something else: an overhead travelling crane. A travelling bridge girder runs on crane rails along the long sides of the building, and a hoist trolley travels along it. Because the bridge moves in one direction and the trolley in the other, the hook can reach almost any point in the building. The usage is common in Belgium and in translated technical documentation.
Related terms
- Bridge abutment
- Span
- Load bearing
- Structural steel sections
- Lift bridge
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