BRIDGE DESIGN PROJECT

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BRIDGE DESIGN PROJECT
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The Task

• Your team is competing for the contract to design
  and build a new bridge in a high-profile location
• The client placing the order will be visiting
  today and your team has been asked to develop a
  small-scale model to demonstrate your proposed
  design

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The Task

• The client will judge the competing designs on
  the basis of
• The maximum load it can support at mid span
• The maximum load divided by the weight of the
  bridge (a measure of efficient use of materials)
• Aesthetic appeal

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Design Requirements

• The bridge must span a gap of 1.0 m
• The deck (walkway) width must be between 0.1 m
  (minimum) and 0.2 m (maximum)
• The bridge must be of a single span design
• The bridge may be rigidly fixed to one side of
  the gap only

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Design Requirements
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Materials

• Cardboard sheet
• A4 paper unlimited within reason
• String not to be used for lashings
• Masking tape for tube manufacture and box edge
  reinforcement only
• Nuts and bolts

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Equipment

• Scissors
• Stanley knife
• Hole punch
• Tube roller
• Hot glue gun
• General tool kit
• Steel ruler

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Objectives 1

• To give a taste of what Engineering is all about
• Problem solving
• Being creative an Engineer is by definition an
  ingenious person
• Team work
• Rewarding
• Fun

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Objectives 2

• Introduction to the Engineering Design process
• from concept to competition
• Make immediate use of new knowledge

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Design/Build/Test Process

• Requirements specification
• (What needs to be designed)
• Generate ideas/concepts
• Evaluate/assess concepts
• Detailed design
• Manufacture
• Test

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Design/Build/Test Process

• Requirements specification
• (What needs to be designed)
• Generate ideas/concepts
• Evaluate/assess concepts
• Detailed design
• Manufacture
• Test

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Project Timetable

• Introduction to Design Task 10 minutes
• Introduction to Bridge Design 20 minutes
• Design Session 30 minutes
• Construction Session 120 minutes
• Test Session 30 minutes

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An Introduction to Bridge Design

• Geoff Parks

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Types of Bridge

• Beam Bridges
• Box Girder Bridges
• Arch Bridges
• Truss Bridges
• Suspension Bridges
• Cable Stayed Bridges

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Beam Bridges
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Beam Bridges

• A beam bridge is the simplest kind of bridge
• The farther apart its supports, the weaker a beam
  bridge becomes
• Cheap and cheerful
• Easy to manufacture
• Not very beautiful
• Beam needs careful design

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Box Girder Bridges
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Box Girder Sections
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Box Girder Bridges

• Similar to beam bridges
• With well designed girders will be stronger than
  a simple beam bridge
• Cheap and cheerful
• Easy to manufacture
• Not very beautiful
• Girder needs careful design

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Supporting Beams

• To improve the performance of a simple beam
  bridge the beam has to be supported
• There are three basic ways to do this
• Arches
• Trusses
• Cables

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Arch Bridges
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Arch Bridges

• Arch bridges are one of the oldest types of
  bridge and have great natural strength
• Instead of pushing straight down, the weight of
  an arch bridge is carried outward along the curve
  of the arch to the supports at each end
• These supports (called abutments) carry the load
  and keep the ends of the bridge from spreading out

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Arch Bridges
Over
Under
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Arch Bridges

• Very strong if well designed
• Can be very beautiful
• Tend to be very heavy
• Need very strong abutments

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Truss Bridges
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Truss Bridges

• Are mostly empty space, but very effective
• Solid components (beams, arches etc.) are
  replaced by triangulated assemblies of thin
  (usually metal) members

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Truss Bridges

• Very good strength to weight performance
• Possibility of lots of repeated parts reduces
  manufacturing costs
• Can be incorporated into almost any design
• Can be very beautiful
• Lots of parts to be manufactured

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Suspension Bridges
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Suspension Bridges

• Apart from the towers, all the highly stressed
  parts of a suspension bridge are in tension
• A suspension bridge suspends the roadway from
  huge main cables, which extend from one end of
  the bridge to the other
• These cables rest on top of towers and are
  secured at each end by anchorages

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Suspension Bridges

• Aesthetic, light and strong
• Can span distances far longer than any other kind
  of bridge
• The most expensive bridges to build
• Susceptible to wobble if badly designed

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Suspension Bridge Wobble
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Cable Stayed Bridges
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Cable Stayed Bridges

• In suspension bridges, the cables ride freely
  across the towers, transmitting the load to the
  anchorages at either end
• In cable-stayed bridges, the cables are attached
  to the towers, which alone bear the load

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Cable Stayed Bridges
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Cable Stayed Bridges

• Undeniably beautiful
• Compared to suspension bridges
• Require less cable
• Are easier and faster to build
• Need stronger towers