Different types Movable Bridges and their benefits

Movable bridges are useful since these can alter their location as well as the shapes with the purpose of making the passage for vessels and boats in the waterway.

The construction cost is low for this type of bridge as no high piers and long approaches are required for construction. This type of bridge is specifically constructed for river traffic.

These movable bridges can be easily repaired with lighter materials and their gears can be substituted with hydraulics.

Categories of Movable Bridges: Given below, the detail lists of most common types of movable bridges as well as special movable bridges.

• Bascule bridge
• Swing bridge
• Vertical lifting bridge
• Special types of movable bridge

Bascule Bridge: Bascule Bridge is secured and supported on an axis that is perpendicular to the longitudinal axis of bridge (affixed like a hinge).

This Bridge is also known as drawbridge. The horizontal axis on which the bridge is hinged is situated at the center of gravity with the intention that a balance is produced among the weights of the bridge on either sides.

Two leading types of bascule bridges are found which range from single leaf bascule and double leaf Bascule Bridge. Besides, there also exist triple and quadruple bascule bridges but they are seldom utilized based on the situation. ‘Leaf” is the vital segment of the bridge that pivots relating to the horizontal axis and opens the water traffic.

This type of movable bridge provide the following benefits :-

• It’s structural strength is good
• Consistent
• Construction and operations are cost-effective

Vertical Lifting Bridge: This type is mostly constructed and recognized. It comprises of a span with a common type of truss that is supported with the towers at the end of span. Usually, the weight of this span is counterbalanced. The waterway is uncovered by facilitating the span moving in the vertical direction.

If the machinery liable for the up and down movement of the span is settled on the span itself, then it’s known as span drive vertical lift bridge. But if that machinery is settled on the towers, then it is known as tower drive vertical lift bridge.

These bridges have considerably good stability and as a result they are suitable for locations where long spans are necessary.

Double vertical Lifting Bridge

Swing Bridge: This type of bridge is settled on the horizontal plane that revolves on vertical axis with the purpose of providing passage for the water traffic. A pivotal pier belongs to a normal pier on which a bearing is set up and the horizontal plane stands on this pivotal pier. When the water traffic is closed, the ends of span of this bridge stand on the abutments.

When the water traffic should be uncovered, the ends span should have been free and are only supported with the pivotal pier. So, the end of swing span is lifted with machineries. The swing bridge shifts horizontally around vertical axis unlike other bridges which shift vertical direction.

In order to bear the traffic and resist overstressing, the swing bridge should provide support to both horizontally and vertically. The truss or plate girder creates the span of swing bridge. But the application of plate girder is more cost-effective.

Besides, there are following types of special movable bridges. But they are seldom built up.

Pontoon retractile, Pontoon bridge, Shear pole swing, Folding bridge, Curling bridge, Removable spans bridge, Submersible bridge, Tilt bridge, Transporter bridge, Jet bridge etc.