You might have heard about bridges that can be moved for allowing passage for boats and ships. How is it possible? The answer is HYDRAULICS. Hydraulic bridge or movable bridge is an example from our hydraulic industry. You can find other alternatives like creating a tunnel beneath the river or creating a bridge in a specific height above the river. But, both this won’t be the best solution when considering some technical and economic reasons. For movable hydraulic bridge models, road transportation needs to be closed for water transportation. Tower Bridge, London, England; Gateshead Millennium Bridge, Newcastle, England; Pont Jacques Chaban-Delmas, Bordeaux, France; Puente de la Mujer, Buenos Aires, Argentina; etc.. are some of the famous movable bridges in the world.

When you consider the history of the movable bridge, you can find their existence before the twentieth century. But, the traditional approach used manpower for bridge operation. The integration of hydraulic gears with the existing hydraulic bridge models was introduced from the beginning of 20th century onwards. Smooth and accurate acceleration and deceleration, positive locking in any conditions, driving end locks, safe and easy operations, and ability to carry varying loads are some advantages of the hydraulic bridge.

Pascal’s law is the principle behind hydraulic bridge working. The hydraulic bridge uses petroleum-based hydraulic fluids for operations. Hydraulic motors and hydraulic cylinders are two important components used for powering the bridge with hydraulics. For a bridge operation, the amount of gearing required is dependent on the type of hydraulic motor. The hydraulic cylinders can be divided into tie rod and welded depending on the construction. The welded hydraulic cylinder is suitable for providing longevity for the bridge. Counterbalance valves used in the structure will help to carry varying loads and hold the bridge firmly in any position. Smooth and accurate acceleration and deceleration are provided by the proportional valve used.

Also Check: Examples of Hydraulic System

Bascule bridge, swing bridge, and lifting bridge are three important types of hydraulic bridges.

Bascule Bridge

The Bascule bridge is a subcategory of drawbrige[hinged at an end and pulled up using metal chain]. These bridge can be a single leaf or double leaf. Single leaf bascul bridges[also called rolling bascule bridge] are similar to drawbridge. Whereas, the double leaf bascul bridges will split in the middle. These bridges are structurally sound, reliable, and economical.

Swing Bridge

The swing bridge use a rotating design. It will rotate at an angle of 90° in most cases. The rotating structure will be present at the centre or at both ends of the bridge.

Lifting Bridge

Lifting bridges will move the bridge surface in vertical direction for opening water transportation. Another type of lifting bridge is double vertical lifting bridge, which is divided into two parts and balanced by a central tower. This lifting bridges are suitable for location requiring long spans.