Balsa Wood Bridge Design

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Balsa Wood BridgeDesign

• Group AAA
• Jim Bowen

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Group AAA Division of Labor

• Jim Bowen did all the work
• Bridge design, construction, testing
• Matlab program development
• Oral and written presentation writing

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Group AAA - Bridge Design and Testing Methods

• Started with the simplest 5 node trapezoidal
  truss
• tried different member sizes to see how weight
  and strength varied
• chose .25 x .50 as member size
• wrote a Matlab script to see how top node spacing
  affected weight and strength (see figure)
• tested some 5 node trusses that used .25 x .25
  members

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Group AAA - Bridge Information

• Bridge dimensions
• 24.5 long, 5.5 high, 4.0 wide
• Truss configuration
• Warren through truss
• Bridge numbers
• 10 nodes (5 per truss)
• 14 members
• 1 member type (.25 x .50)

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More Bridge Information

• Estimates for Matlab program
• Weight 67 grams (struts gusset plates extra)
• Strength 192 lb
• Cost 15.9 million
• Benefit 95.6 million
• Profit 79.7 million
• Special features of groups work
• used Matlab program to test many different
  candidate designs

Questions?