HYDRAULIC ASSISTED BRIDGEIshan Kossambe

13MCD0038

Introduction• Incorporates an integrated hydraulic system into the

bridge in order to carry more weight• Suitable for arch based bridges

How it works

• Forces in a lateral/horizontal direction at the supports

• Three hinged arch

• Loading will cause the arch to spread

Supports

• Load causes the three hinged arch to spread out

• Piston is held in place via a pined connection

• O-rings of the piston

Mid-Span of Bridge• The high pressure hydraulic fluid causes another piston to

become raised

• Counteracting the load

•  Calibration and calculation is required by changing the diameter of the piston and shafts

Advantages

• Little maintenance• Quantity of material required to construct the bridge is reduced

• Increase its aesthetic and social impact

• Reversal of hydraulic fluid still results in equilibrium

Disadvantages• Vertical hydraulic column being required to be located in

the center of the arch• Vertical column type hydraulic bridges may never be used

in arch bridges required to span gaps which are very high in the context of the altitude of the locale.

• Failure by very high force

 Overcoming the Disadvantages

• Eliminating the single vertical hydraulic column

• Replacing hydraulic components placed at an angle

• Adding several, thicker O-rings and gaskets 

Potential Applications• Pedestrian Footbridges• Water Transportation• Vehicular Transportation• Light Vehicles• Freight Vehicles• Railway Transportation

Moving Bridges• Drawbridge• Bascule bridge• Curling bridge• Vertical-lift bridge• Retractable bridge• Tilt bridge

Hydraulic Systems for Movable Bridges

•Objectives• Ability to handle varying loads • Smooth acceleration and deceleration• Positive locking in any position

Hydraulic Cylinders

• Two per span• Tie rod and welded• Intermediate trunnion and

spherical bearing clevis both ends

• The national fluid power association (NFPA) established a standard for tie rod type hydraulic cylinders

• Tie rods should be inspected for corrosion damage

Counterbalance Valves• Varying loads, wind makes it unbalanced and causes run

away• A counterbalance valve keeps this condition in check• Holding the bridge firmly in any position• Acts as a check valve

Proportional Valves• Smooth acceleration and deceleration• Gradually increasing or decreasing the amount of flow to

the cylinders• The use of servo valves for this task is not recommended• 0 - 9 volts dc/800 milliamps

Hydraulic Pump• Variable volume-bent axis-piston type pump• Strong suction capability and greater dirt tolerance, make

them a good choice for movable bridge• Pumps which require a boost or supercharge only add

complexity to the design• Horsepower limiter

Hydraulic Fluids

ISO Grade Viscosity Normal Operating Temperature

AW32 Light 1O0-150°F

AW46 Medium 3O0-160°F

AW68 Heavy 4O0-170°F

Care to be Taken While Designing• Pumps and motors should be accessible for work• Vibration mounts and hoses to isolate pump VIBRATION• The use of ANSI standard bolt pattern sub plate mounted

valves• Drilled manifolds to minimize piping and fittings• Filters which are easy to change with good clogging

indicators• Straight thread "o” ring ports and fittings• Large access covers for reservoirs

The Rolling Bridge• Completed in 2004 as part of the Grand Union

Canal office & retail development project at Paddington Basin, London.

• Despite the connotation of its name, it is more accurately described as "curling".

• Designed by SKM Anthony Hunt with Packman Lucas, and built by Littlehampton Welding Ltd.

• The Hydraulic design and development was done by Primary Fluid Power Ltd in the North West.

• In 2005, the bridge won the British Structural Steel Design Award.

References• http://en.wikipedia.org/• http://www.designingbuildings.co.uk/wiki/

Hydraulic_Assisted_Bridges• www.youtube.com• Hydraulic systems for movable bridges by Michael A.

Henley