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Hydraulic assisted bridges
The document discusses hydraulic assisted bridges, highlighting their design that incorporates an integrated hydraulic system to support greater weights, particularly for arch-based structures. It outlines how the hydraulic mechanism works, its advantages like reduced material needs and low maintenance, but also its disadvantages, such as requiring a central vertical column. Different applications for movable bridges and hydraulic systems are presented, alongside an example of the rolling bridge in London.
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Hydraulic assisted bridges
- 1.
- 2. Introduction • Incorporates anintegrated hydraulic system into the bridge in order to carry more weight • Suitable for arch based bridges
- 3. How it works •Forces in a lateral/horizontal direction at the supports • Three hinged arch • Loading will cause the arch to spread
- 4. Supports • Load causesthe three hinged arch to spread out • Piston is held in place via a pined connection • O-rings of the piston
- 5. 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
- 6. 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
- 7. Disadvantages • Vertical hydrauliccolumn 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
- 8. Overcoming the Disadvantages •Eliminating the single vertical hydraulic column • Replacing hydraulic components placed at an angle • Adding several, thicker O-rings and gaskets
- 9. Potential Applications • PedestrianFootbridges • Water Transportation • Vehicular Transportation • Light Vehicles • Freight Vehicles • Railway Transportation
- 10. Moving Bridges • Drawbridge •Bascule bridge • Curling bridge • Vertical-lift bridge • Retractable bridge • Tilt bridge
- 11. Hydraulic Systems forMovable Bridges •Objectives • Ability to handle varying loads • Smooth acceleration and deceleration • Positive locking in any position
- 12. Hydraulic Cylinders • Twoper 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
- 13. Counterbalance Valves • Varyingloads, 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
- 14. Proportional Valves • Smoothacceleration 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
- 15. Hydraulic Pump • Variablevolume-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
- 16. Hydraulic Fluids ISO GradeViscosity Normal Operating Temperature AW32 Light 1O0-150°F AW46 Medium 3O0-160°F AW68 Heavy 4O0-170°F
- 17. Care to beTaken 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
- 18. 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.
- 19. References • http://en.wikipedia.org/ • http://www.designingbuildings.co.uk/wiki/Hydraulic_Assist ed_Bridges •www.youtube.com • Hydraulic systems for movable bridges by Michael A. Henley