Bridges

1
Bridges

• Designed for Forces
• Form, Function, and Fashion

2
Arch Frame Bridges

• Weight and forces are spread over the entire
  arch.
• Date back to Roman Times
• Good for making over rivers.

3
Cable Stayed Bridge

• Cables and Columns work together to support the
  weight and forces.
• Cables become very tight when bridge is used.

4
Girder Bridge

• Columns take the weight and stress from the
  forces on the bridge.
• Disadvantage Many columns must be used.

5
Rigid Frame Bridge

• Strong bridge
• Supports Weight and Forces well
• Disadvantage Costly because it takes lots of
  material to build.

6
Suspension Bridge

• Cable and Columns work together to support forces
  on bridge.
• Few columns needed because of the cables.

7
Truss Bridge

• Stick like framing provides support for weight
  and forces on the bridge.
• Lower cost than other bridges but less decorative.

8
Toothpick Bridges
9
Your Challenge

• Build a 300-400 toothpick bridge out of standard,
  double-pointed toothpicks.
• Use only white glue. No wood glue, Gorilla glue,
  or crazy/super glue.
• Time will be about 1 week.
• The bridge must be more than 20 cm long, but not
  longer than 25 cm
• Bridge must have four sides
• Height at least one toothpick tall
• Width at least one toothpick wide
• You must draw a preliminary drawing of your
  bridge before you start work on the bridge.

10
Steps of Construction

• Line toothpicks to make the length of the bridge.
• Note ends of toothpicks are staggered.
• Bundles of 3 toothpicks are stronger.

11
Providing Truss Supports

• Framing of bridge should be done using triangles.
• Triangles provide for excellent support when
  forces are applied.

12
Footing of the Bridge

• Note the use of angled supports.
• Again the triangular design distributes the
  forces over a greater area.