Bridge Building
Objective:
Your group is to work as a Designing and Engineering Team. The challenge is to build, using only the materials provided, a bridge with the best Efficiency rating. The Efficiency rating is a method to test the bridge by dividing the strength of the bridge by the weight of the bridge.
Engineering can be thought of as the science of building roads, bridges and other structures. To complete this unit you and your partner are going to research and study bridge building designs; Construct and test for efficiency a model Truss Bridge according to the bridge building code and complete a summary report about your project.
Equipment: Materials (bridge building kit)
Procedure:
Step 1: Get set up
Step 2: Introduction
Read "History of Bridge Development" (Appendix A - Below) and complete the question sheet. (get the sheet from your instructor)
Step 3: Preparation
Research bridge building and design using the Internet. (go to one of the free computers)
Check out the following sights:
www.pbs.org/wgbh/nova/bridge - Click on Build a Bridge and complete the steps.
www.ce.ufl.edu/activities/trusslab/trussndx.html - Check out the Truss Bridge Laboratory
www.pre-engineering.com/resources/trusses.htm - Example Bridge trusses.
Step 4: Designing your model Truss Bridge
Using a piece of graph paper complete a drawing (side view) of the bridge you plan to build. Be sure to make the drawing of your bridge the actual size and make it according to the bridge building code Appendix A.
Goal - design and build a bridge that is very light in weight but at the same time, very strong. More toothpicks may make it stronger, but will also make it a lot heavier.
Step 5: Start Construction on your Truss Bridge
1) Place the wax paper over your final drawing of your Truss Bridge to protect it from the glue. Using the toothpicks and glue make a side of the bridge as accurately as you can. Be sure to glue the toothpicks to each other, rather than to the wax paper.
2) When one side is done, gently remove the wax paper and toothpicks and make a second side.
3) When both sides are completed, they need to be joined by glueing a few toothpicks from side to side along the top and bottom.
4) Next lay the cardboard roadbed on the bottom toothpicks. (get the cardboard from your instructor)
5) Once you have completed your bridge, use the digital camera to take a picture of it and save it to the proper directory.
Step 6: Testing your Truss Bridge
1) Once the glue is dry, the bridge is now ready for testing. Get the instructor to weigh and test the bridge for strength.
2) You will need to calculate the Efficiency of your design by using the following formula:
Step 7: Write a report
Don't forget to write a report. Check out the Tech Lab web page Written Report link for instructions on writing your report. Also include the following information:
Objective:
Your group is to work as a Designing and Engineering Team. The challenge is to build, using only the materials provided, a bridge with the best Efficiency rating. The Efficiency rating is a method to test the bridge by dividing the strength of the bridge by the weight of the bridge.
Engineering can be thought of as the science of building roads, bridges and other structures. To complete this unit you and your partner are going to research and study bridge building designs; Construct and test for efficiency a model Truss Bridge according to the bridge building code and complete a summary report about your project.
Equipment: Materials (bridge building kit)
- Below is a list of the materials you will need: "History of Bridge Development" sheet.
- "History of Bridge Development - Questions" sheet (supplied by Instructor)
- Bridge Building Code (Appendix B - Below)
- Graph paper (supplied by Instructor)
- Roadbed (supplied by Instructor)
- Wax paper (supplied by Instructor)
- Glue gun, glue sticks, & toothpicks (supplied by Instructor)
Procedure:
Step 1: Get set up
- Click on the “File Explorer” icon on the desktop. (bottom of the screen)
- Click on the arrow in front of This PC and choose the Home Drive (U:)
- Choose New Folder from the top of the page. .
- Name the folder “yourclass_bridge” Example 7A_bridge.
- Now exit all boxes that you have open on your screen.
Step 2: Introduction
Read "History of Bridge Development" (Appendix A - Below) and complete the question sheet. (get the sheet from your instructor)
Step 3: Preparation
Research bridge building and design using the Internet. (go to one of the free computers)
Check out the following sights:
www.pbs.org/wgbh/nova/bridge - Click on Build a Bridge and complete the steps.
www.ce.ufl.edu/activities/trusslab/trussndx.html - Check out the Truss Bridge Laboratory
www.pre-engineering.com/resources/trusses.htm - Example Bridge trusses.
Step 4: Designing your model Truss Bridge
Using a piece of graph paper complete a drawing (side view) of the bridge you plan to build. Be sure to make the drawing of your bridge the actual size and make it according to the bridge building code Appendix A.
Goal - design and build a bridge that is very light in weight but at the same time, very strong. More toothpicks may make it stronger, but will also make it a lot heavier.
Step 5: Start Construction on your Truss Bridge
1) Place the wax paper over your final drawing of your Truss Bridge to protect it from the glue. Using the toothpicks and glue make a side of the bridge as accurately as you can. Be sure to glue the toothpicks to each other, rather than to the wax paper.
2) When one side is done, gently remove the wax paper and toothpicks and make a second side.
3) When both sides are completed, they need to be joined by glueing a few toothpicks from side to side along the top and bottom.
4) Next lay the cardboard roadbed on the bottom toothpicks. (get the cardboard from your instructor)
5) Once you have completed your bridge, use the digital camera to take a picture of it and save it to the proper directory.
Step 6: Testing your Truss Bridge
1) Once the glue is dry, the bridge is now ready for testing. Get the instructor to weigh and test the bridge for strength.
2) You will need to calculate the Efficiency of your design by using the following formula:
Step 7: Write a report
Don't forget to write a report. Check out the Tech Lab web page Written Report link for instructions on writing your report. Also include the following information:
- Did you like the project? Why?
- Did everyone in your group work well together?
- Did you learn a lot of different things by doing this project? What sort of things?
- What was the toughest part of this project? Why?
- What did you enjoy most about the project? Why?
- Do you think you would like to actually be working with a company like this, doing work like what you've done with this project?
Appendix A - History of Bridge Development
Basic bridge designs are developed from natural bridges - a tree trunk that has fallen across a stream, vines hanging over a river, or stones that make a stepping-stone path across a shallow stream. These natural bridges were probably built upon by ancient bridge builders. For example, someone may have built up the stepping stones, placed flat stone slabs or logs on top of them, and connected the stones to create a low bridge. This type of bridge is called a "clapper bridge." It is one of the earliest bridge constructions. Such simple bridges are probably still built today in many places. In general, though, bridge construction has changed greatly.
The ancient Romans refined bridge building with two important contributions. Nearly all of their bridges used the arch design - a structure that can support more weight than a flat surface can. Also, the Romans' discovery of natural cement allowed them to build strong, long-standing bridges. Many of these ancient Roman bridges are still standing today.
There were excellent bridge builders in Asia, too. Some early bridges in Asia used a cantilever design. This design enabled the builder to make simple, long-span bridges across fairly wide rivers. One famous bridge in China, built about 1300 years ago, is the Great Stone Bridge. Its graceful arch shape is not the same type of arch used by the Romans. Instead, this bridge is quite low, and the arch is very shallow.
The Renaissance brought new scientific ideas to bridge building. Leonardo da Vinci and Galileo developed theories about the strength of building materials. Their theories have helped architects understand how to make strong structures from lightweight materials. Bridge building became more exact as people began to use more mathematical theories about it. Another new development that changed bridge building was the development of metal.
About 200 years ago, the first cast-iron bridge was built. This was the Iron Bridge at Coalbrookdale in England. Before that time, bridges were made of stone, brick, clay, or timber. Eventually, wrought iron was used instead of cast iron. Much later, steel was used. Many new bridge designs were created and tested during this time. The Britannia Tubular Bridge, completed in 1850, showed one such new development. It was built from rectangular tubes of wrought iron. Similar tube sections are often used in bridges today.
Other important developments came with the truss bridge and the suspension bridge designs. The truss is an old design, but it was improved when engineers knew enough about science and mathematics to work out the mechanics of the design. Covered bridges were usually built on the truss design. Truss bridges were improved even more when metal was used. The suspension bridge was another basic design that was changed by the use of metal. The Brooklyn Bridge is one famous suspension bridge built during this time. It uses steel wires for the suspending cables.
About a hundred years ago, engineers began using concrete for bridges. A new method called "prestressing " helps prevent concrete from cracking after a structure is built. Today, most new bridges are made of prestressed concrete and steel.
The ancient Romans refined bridge building with two important contributions. Nearly all of their bridges used the arch design - a structure that can support more weight than a flat surface can. Also, the Romans' discovery of natural cement allowed them to build strong, long-standing bridges. Many of these ancient Roman bridges are still standing today.
There were excellent bridge builders in Asia, too. Some early bridges in Asia used a cantilever design. This design enabled the builder to make simple, long-span bridges across fairly wide rivers. One famous bridge in China, built about 1300 years ago, is the Great Stone Bridge. Its graceful arch shape is not the same type of arch used by the Romans. Instead, this bridge is quite low, and the arch is very shallow.
The Renaissance brought new scientific ideas to bridge building. Leonardo da Vinci and Galileo developed theories about the strength of building materials. Their theories have helped architects understand how to make strong structures from lightweight materials. Bridge building became more exact as people began to use more mathematical theories about it. Another new development that changed bridge building was the development of metal.
About 200 years ago, the first cast-iron bridge was built. This was the Iron Bridge at Coalbrookdale in England. Before that time, bridges were made of stone, brick, clay, or timber. Eventually, wrought iron was used instead of cast iron. Much later, steel was used. Many new bridge designs were created and tested during this time. The Britannia Tubular Bridge, completed in 1850, showed one such new development. It was built from rectangular tubes of wrought iron. Similar tube sections are often used in bridges today.
Other important developments came with the truss bridge and the suspension bridge designs. The truss is an old design, but it was improved when engineers knew enough about science and mathematics to work out the mechanics of the design. Covered bridges were usually built on the truss design. Truss bridges were improved even more when metal was used. The suspension bridge was another basic design that was changed by the use of metal. The Brooklyn Bridge is one famous suspension bridge built during this time. It uses steel wires for the suspending cables.
About a hundred years ago, engineers began using concrete for bridges. A new method called "prestressing " helps prevent concrete from cracking after a structure is built. Today, most new bridges are made of prestressed concrete and steel.
Appendix B - Bridge Building Code
1. The bridge must cover a span of 30 centimeters.
2. The bridge must be 8 centimeters wide.
3. When building the bridge, apply glue sparingly only to join the toothpicks. (Entire toothpicks should not be covered with glue)
4. The toothpicks may be shortened, bent, blunted, or spliced. Two or more toothpicks can not be bundled together to make them stronger.
5. The opening in the roadbed is used to hang the weights for testing, do not build supports or braces across this opening.
2. The bridge must be 8 centimeters wide.
3. When building the bridge, apply glue sparingly only to join the toothpicks. (Entire toothpicks should not be covered with glue)
4. The toothpicks may be shortened, bent, blunted, or spliced. Two or more toothpicks can not be bundled together to make them stronger.
5. The opening in the roadbed is used to hang the weights for testing, do not build supports or braces across this opening.