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TO BUILD YOUR OWN BRIDGE

How to Use This Program

To add a feature to the worksheet click on the pencil , click on what you want, such as the abutement , then click where you want it to appear.

To erase, click on the eraser , then click on what you want to erase.

To move something. Click on the pointer , then click-hold-and-drag the item you want to move, such as the abutement.

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Bridge-building basics

(1) First, build your abutements .

(2) Make sure you have a 19th century sign or a 21st century sign on the road to the left of your worksheet.

(3) Make sure there's a green tree on the road on the right of your worksheet.

(4) Add your bottom chords. There has to be a bottom chord (which is what the vehicles travel on).

(5) Add your trusses . From approximately the center of your bridge you will want the braces to point (lean) towards the abutements.

(6) Add your top chords, , (which holds the brace in place).

(7) Click on RUN to run your simulated bridge.

Here is an example of a finished bridge. You can also decorate your bridge with a roof and a portal at each end. For the purpose of this simulation these features have no function.

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Additional Stuff

Plot

As the simulation plays, in a separate window from the simulation you will see a graphic plot of the total load on the bridge – that is, the total load from all the vehicles on the bridge at any particular time (you may have to click on the Window menu of the browser to see the plot).

The higher the green line, the greater the load on the bridge. The red line shows the maximum this bridge can support. If the green line crosses the red line (as in the example above), the bridge will break. You can change this value by changing the simulation properties (see below).

Simulation properties

If you select simulation properties you get the window below where you can change many values used in your bridge. The numbers used are an approximation of pounds. What is important here is to see the relative affect of changing one value or another.

You can change the maximum weight capacity of the bridge (max_capacity). The higher the number, the more it can hold. You can change the capacity of any one truss (truss_limit), or you can change the weight of any of the various vehicles. At any time you can return to the original values of the simulation by clicking on Reset in the simulation.