Balsa Wood Bridge Design

Extension Project

Beginner's Guide to the Bridge Designer

Chapter 1: Introduction The Bridge Designer is a simulator that you make bridges on. A truck drives over it to test your bridge. There are ten different bridges and many ways to make each one.

If you don’t have the Bridge Designer downloaded on your computer go to for the free download


Chapter 2: Tools

 This Is How You Create A New Bridge.

This Is To Open An Existing Bridge.

This Is Used To Save The Bridge You Are Creating.

This Is Used To Print Your Bridge.

This Is To Test Your Bridge With The Truck.

To Select All Members And Joints

This is to erase selected members and joints.

This is to undo and redo.

This is for the previous and next bridge design iterations.

This shows how much your bridge costs.

This shows how much money each individual part of your bridge costs.

Status shows how safe your bridge is.

This Is How You Get From


These are the types of steel you can use in the      Bridge Designer.

These are the types of bars you can use in the Bridge


These are how thick your bars are allowed to be. They range from 30x30 to 500x500.

These buttons make the tube sizes bigger and smaller. For example, 380x380 to 390x390.

These are the most important tools you use in the Bridge Designer. Left to right are: joints, members (bars), select and erase.

When you’re checking your bridge there are some more controls:

Background: The background is the river and the cliffs.

Abutments: The abutments are the supports (bricks at either side) of the bridge.

Truck: Is the truck. If you deselect it, the truck goes away.

Colors: The colors are the blue (tension = being pulled apart) and the red (compression = being pushed together).

Exaggeration: The exaggeration shows you the way the bridge sags or collapses.

Smoothing: The smoothing is whether the background looks smooth or rough.

Chapter 3: How to Make a Bridge

There are ten different sample bridges provided by the Bridge Designer.

If you load a sample of a bridge you choose which one you want from the list, but if you start a new bridge it automatically goes to suspension bridge, 44 meters:

It always starts like this but if you don’t want the Members window the you can click on the x,, and it disappears:

But if you want it back you just click on the little arrow in the top right hand corner i

This is a demonstration of a bridge on the Bridge Designer:

it reappears:

This is a demonstration of a bridge on the Bridge Designer:

You start with your joints:

then the members:

At any time you can check you bridge with the truck by pressing

This is what this bridge looks like:

At the moment it sags a little but you can put in reinforcements to make it stronger. Put a row of joints under the first one:

Then add the members:

Now it’s flatter again:

That’s one of the many ways to make a bridge with the Bridge Designer.

Chapter 4: Suspension Bridge

(44 meter span)

There are three different types of suspension bridges in the Bridge Designer. The first one on the list is a 44 metre span bridge. If you want to load a sample of a suspension bridge it looks like this:

and you can always start with your own design by pressing

Again, you start with your joints:

Then members:

Then try out your bridge:

That’s a Suspension Bridge 44 meter span.

Chapter 5: The Different Bridges and How to Build Them

Some of the bridges available in the Bridge Designer are:

Suspension Bridge 44 meter span:

Suspension Bridge 20 meter span:

Pratt Deck Truss 44 meter span:

Warren Thru Truss 20 meter span:

Continuous Arch 24 meter span:

Howe Through Truss With High Pier 32 meter span:

Cable-stayed Bridge 40 meter span:

Suspension Bridge 40 meter span:

Warren Deck Truss With Low Pier 32 meter span:

Combined Truss Bridge 36 meter span:

With every bridge you build you start the same way:

1. Joints

2. Members

3. Check your bridge

4. If your not happy with your bridge make it stronger

5. If you are happy with your bridge, save it.

Chapter 6: Examples

Here are three of my cool looking bridges (none of them are perfect):

You can also sometimes see the truck make the bridge collapse:

Or the bridge collapse itself:

That concludes my detailed bridge design tutorial i hope it helped.

Required Materials