1. Building for Strength and Distance
Bridges
Building for Strength and Distance

2. Bridges are built to be strong, as well as cover a distance
We will look at five types of bridges:
Arch Beam
Cable-Stay
Truss
Suspension

3. Arch Bridges Arch bridges have been used for over 3000 years.
Because an arch bridge is curved, the loads are pushed along the curve of the arch to the supports at the end.
Until the two ends of the arches are combined, the bridge is unstable.

4. Beam Bridges Beam bridges are the simplest type.
They need to be stiff, and not twist or bend.
The weight of the beam pushes down on the supporting piers.
The farther apart its supports are,
the weaker the bridge gets.

5. Suspension Bridges
Suspension bridges were once made from rope and wood. Now, they are made using high tensile steel cables.
They are both light and strong, and can span much longer gaps than other types of bridges. They are also usually the most expensive bridge to build.
The cables are anchored into the supports at either end of the bridge, and distribute the weight evenly along the anchor points along the bridge.

6. Cable-Stay Bridge
Unlike a suspension bridge, this bridge doesn’t require anchorages or two towers.
The cables run from a the road to a single power that bears the weight.
The first cable-stay bridge was built in the 16th century. They are cheaper than suspension bridges and are faster to build.

7. Truss Bridges
Truss bridges are the oldest bridges. They are also some of the cheapest ones.
They are composed of a “truss,” which has connected elements that form triangles.
The weight is distributed among
the triangular elements.

8. Engineering Design Process
You need to draw out a plan for your bridge, and remember that you have limited materials.
After you plan, you need to construct your bridge...then test it.
Make changes to improve your design...and record them! Did the changes help, or hurt?
Remember...you can’t compete without an Engineering Design Worksheet!!!

9. Kindergarten-2nd Grade Challenge
Materials:
40 straws 60 cm of string
10 paper clips 5 index cards Masking tape
Build a bridge that is strong enough to hold a plastic cup filled with marbles. Your bridge may NOT be attached to the table.
Your bridge be at least 20 cm tall, and must span a gap that is at least 30 cm long.
The bridge that holds the most marbles wins!

10. 3rd-4th Grade Challenge
Materials: 30 straws 60 cm of string masking tape
Build a bridge that is strong enough to hold a plastic cup filled with marbles. Your bridge may NOT be attached to the table.
Your bridge be at least 20 cm tall, and must span a gap that is at least 40 cm long.
The bridge that holds the most marbles wins!

11. 5th-8th Grade Challenge
Materials: 30 straws 60 cm of string 4 feet of masking tape
Build a bridge that is strong enough to hold a plastic cup filled with marbles. Your bridge may NOT be attached to the table.
Your bridge be at least 20 cm tall, and must span a gap that is at least 50 cm long.
The bridge that holds the most marbles wins!