Design of Hydraulic Transfer Bridges

Transfer Bridges are used to transfer automobiles, railcars or pedestrians from land based to water based transportation systems or vice versa. For example a ferry ramp that acts as a bridge between land and the ferry is an example of a transfer bridge. Transfer bridges can also be used to transfer rail cars onto and off of car floats. A car float is a barge that has rails mounted on the deck so that rail cars can be pushed onto the barge for transport across a river or harbor.

Car floats rise and fall with the tide. Also the freeboard on the car float changes as the loading on the car float changes. The freeboard is the distance from the waterline to the top of deck.

A transfer bridge needs to accommodate the changes in tide as well as the changes in the car float freeboard due to loading and unloading the car float. Based on the location of the transfer bridge, the magnitude of tidal variations and size and loading of the car floats, the transfer bridge may need to provide 10 foot or more of adjustment so that the car float can mate to the transfer bridge.

Transfer Bridge changes in inclination are accommodated by the use of movable (rotation) heel bearings with/or without pin (trunnion) hinges in the bridge girders. Having additional hinges provides additional adjustment capability, but this comes with additional cost and complexity.

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