Design a Bridge

https://bridgedesigner.org/download/#

MIT+K12: Truss Bridges

Intro:

Demonstrate straw&pin beam- first without diagonals,then with straw and string diagonals- note lengthening and shortening of diagonals as beam is flexed.

A truss keeps all members purely in tension and compression.

Lesson 1:

• Convene in Digital Photo Lab- Open West Point Bridge Designer

• Load Sample Design- Warren Deck Truss 20Meter Span

• Note Initial Cost: $261,000

• Edit name

• "Save As" to student folder

• Review basic Tools

• Load Test

• Revision cycle- In Drawing board mode- select members, reduce size until failure, then increase- maximum cost= $185,000

• Note colors/ ratios--ratios should be >0.6 and <0.95

• Print Out Screen Shot--command+shift +3 or 4

On-line tutorial- WPBD

Demo using 20M Warren Truss

Extra Time- optimize Pratt Deck Truss 44 Meters

LESSON 2: Who will be PONTIFEX MAXIMUS?

Optimizing Member size Using Ratios:

• Review optimizing using load test results:
  Force/strength ratios should be between 0.8 and .99- if greater than 1.0, become bright red or blue(failed!)

• Comparison:

  • A weight lifter can lift 100 lbs.
    If he is lifting 90 lbs, how much of his capacity is he lifting? (0.9)?

  • If he is lifting 100 lbs, he is straining to hold it.(1.0)

  • If he tries to hold up 110 lbs, he is at 110% of his capacity, and he drops it

• Click at top of column to sort by values

• To select a range of values, click on one end of the range, press shift, then click on the other end of the range.

Buildings, bridges, and other structures are not only functional, but need to be beautiful as well-- the forms of the Zakim Bridge echoes not only the Bunker Hill Monument, but the stays of the USS Constitution

Lesson 3:

• Design Original arch bridge with a Cost below $260,000 ($230,000 possible)

Deck Elevation= 24 meters

Arch Height = 12 meters

• New Design

• Select

• • Elevation-24 Meters

  • Arch Abutments; Height of Arch=12 meters

  • No Piers

  • No Anchorages

  • Templates( templates are suggestions only- try making your own design)

  • Design by_______________

• Review optimizing using load test results:
  Force/strength ratios should be between 0.7 and .99- if greater than 1.0, become bright red or blue(failed!)

Note properties of hollow tubes vs bars

Printing the Design:Demo

• • File- Print the Design; ‘Save as’ to student file

  • Color Print of Design:

  • Do Screen Shot of Drawing Board, showing force/strength ratios- (On Mac: Control + Option+3)

  • Print Screen Shot on HP 145

Extra time- work on own design

Lesson 4:

Optimize Cable-Stayed or Suspension Bridge from sample design - Less than $220,000- force/strength ratios should all be 0.7- 0.9.

Note properties of hollow tubes vs bars

Note how components interact

National Geographic Video: Superbridge

• Do Screen Shot of Drawing Board, showing force/strength ratios- (On Mac: Control + Option+3)

• Print Screen Shot on HP 145 printer

Extra Credit: Design "Folly" bridge- Must be functional as well as artistically interesting