What is a table bridge?
A table bridge (Dutch tafelbrug or tafelhefbrug) is a movable bridge whose straight deck is pushed vertically upwards by hydraulic cylinders to let vessels pass. The deck sits on the cylinders like a tabletop on its legs, hence the name. The difference from a conventional vertical lift bridge: there the deck is hoisted up from towers, whereas a table bridge is pushed up from below.
Application
Table bridges are mainly used on smaller waterways where:
- only a limited extra clearance is needed (usually in the order of 1 to 2 metres);
- tall lifting towers are unwanted in the landscape or townscape;
- a movable bridge with little visible machinery is preferred.
Pros and cons
Advantages
– Calm, simple appearance, with no towers or counterweights above the deck.
– With a light deck (for example fibre-reinforced composite), cylinders and drive stay compact.
Disadvantages
– The achievable lift height is limited.
– All cylinders must move exactly in step. If they do not, the deck can tilt or drop uncontrollably, so its balance must be monitored automatically.
– Wind can prevent the deck from settling squarely back onto its bearings.
Trade-off
If the deck only needs to rise a little and there is room for longer approach ramps, a fixed bridge with a raised roadway is often simpler and cheaper to build and maintain.
Related terms
- Lift bridge
- Bascule bridge
- Swing bridge
- Drawbridge
- Beam bridge
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