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 presentation

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Group AAA - Bridge Design and Testing Methods

• Started with the simplest 5 node trapezoidal
  truss
• tried different member sizes and top node spacing
  to see how mass and strength varied
• tested some 5 node trusses that used .25 x .25
  members
• chose .25 x .50 as member size, 14 spacing
• wrote a Matlab script to see how height affected
  mass, strength, and profit (see figure)

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Bridge Design Testing
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Group AAA - Bridge Information

• Bridge dimensions
• 24.5 long, 8.5 high, 4.0 wide
• Bridge numbers
• 10 nodes (5 per truss)
• 14 members
• 1 member type (.25 x .50)
• Truss configuration
• Warren through truss (see figure)

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Truss Design - Group AAA
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More Bridge Information

• Estimates from Matlab program
• Mass 69 grams
• Strength 111 lb
• Cost 26.5 million
• Benefit 29.0 million
• Profit 2.5 million
• Special features of groups work
• used Matlab program to test many different
  candidate designs

Questions?