Swing Bridge - Disadvantages

Disadvantages

• For a symmetrical bridge the central pier forms a hazard to navigation. Asymmetrical bridges may place the pivot near one side of the channel.
• Where a wide channel is not available a large portion of the bridge may be over an area that would be easily spanned by other means.
• A wide channel will be reduced by the centre pivot and foundation.
• When open, the bridge will have to maintain its own weight as a balanced double cantilever, while when closed and in use for traffic the live loads will be distributed as in a pair of conventional truss bridges, which may require additional stiffness in some members whose loading will be alternately in compression or tension.
• If struck from the water near the edge of the span, it may rotate enough to cause safety problems (cf. Big Bayou Canot train disaster).