Overview

The Bridge Designer will provide you with a realistic introduction to engineering through an authentic, hands-on design experience. This software provides you with the tools to model, test, and optimize a steel highway bridge, based on realistic specifications, constraints, and performance criteria.

The Bridge Designer is free and in the public domain. It is provided and intended for educational use only.

How it works

When you start up the Bridge Designer, you are presented with the project requirement--to design a steel truss bridge to carry a two-lane highway across a deep river valley. Using the Design Project Setup Wizard, choose from a variety of different deck elevations and support configurations for your bridge. Each will cause the structure to carry load in a different way, and each has a different cost.

After defining the deck elevation and support configuration, create a structural model by drawing joints and members on the computer screen with your mouse. Each member has its own unique properties--material, cross-section shape, and size. You can define these properties as you design the structure--or just accept the default values and modify them later.

Once the structural model is complete, click the Load Test Button to run a simulated load test of your bridge. This test will determine whether your design is strong enough to carry its specified loads, which include the weight of the bridge itself plus the weight of a standard truck loading.

This simulation includes an animation of your bridge as it is loaded, first by its own weight and then by the truck driving across it. If your design is strong enough, the truck will be able to cross it successfully; if not, the structure will collapse. Note that, during the animation, the structural members change color to indicate how they are loaded--blue for tension and red for compression.

If your bridge collapses, strengthen it by changing the properties of the members that failed--that is, by changing the members' material, cross-section shape, or size. Continue making these adjustments until the structure can successfully carry the truck without collapsing.

Now you have a successful bridge design, but it probably costs a lot more than necessary. To achieve an optimal solution, refine your design to minimize its cost while ensuring that the structure is still strong enough to carry the truck loading. This optimization process might involve changing member properties or modifying the overall configuration of the structure. This is your opportunity for creativity. Have fun!

The Bridge Designer gives you the flexibility to create designs using just about any shape or configuration you want. Creating the design is fast and easy, so you can experiment with many different alternative configurations as you work toward an optimum solution. The process you will use is quite similar to the process used by practicing civil engineers as they design real structures. Indeed, the Bridge Designer itself is quite similar to the computer-aided design (CAD) software used by practicing engineers, and it will help you in the same way that CAD software helps the professionals — by performing all required mathematical calculations, so that you can concentrate on the creative side of the design process.

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:

• 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

• Nova Science Now: Smart Bridges
  Can we engineer bridges that tell us what's wrong with them before it's too late?