[Introduction] [Task] [Process] [Resources] [Evaluation] [Conclusion]
[Teacher Notes] [PowerPoint Presentation Download] [PowerPoint Presentation on the Web]
Introduction
You are a part of a group of structural engineers and you've been given a challenge. You are to design and build a tall and strong structure from a given set of materials at an engineering competition. With this structure, your team must submit a report that proves to the panel of judges that you really know your business and that your structure wasn't the winner by luck but instead by great design. The prize will be a huge construction contract for your firm.
The Task
You have one week to research, design, build, and test your structure. Your structure should be taller than 9 inches and hold at least a 25 pound weight (like one found in the weight room). Your structure will be made from 10 manila file folders and white glue (materials will be supplied by the company hosting the competition.) Your group consists of 4 members.
· Design Engineer - This person will look at designs in nature, shapes in geometry, and designs of packing materials and how this affects the strength of a structure.
· Strength Engineer - This person will look at buildings and building codes to find out what makes them strong enough to hold up to natural forces such as earthquakes, wind, temperature changes, etc.
· Height Engineer - This person will look at skyscrapers and how they are built to see what keeps these giant buildings from falling over.
· Journalist - This person will conduct interviews with community members such as architects, other engineers, city planners, and people in the construction field to gather the most pertinent information.
The Process
The purpose of a building’s structure is to guarantee that the building will stand up under all the loads and forces acting on it: the weights, the pressures, the wind, the forces due to temperature changes, and perhaps even the shaking caused by earthquakes. Engineers want to build structures that won’t collapse and will resist damage. It is also important to make sure that a building will not move around.
You don't have any time to waste. So get started with this plan for your week.
Days 1 and 2: Research
- As a group, investigate equilibrium, rigidity, tension, & compression. (Do this together in class!)
When a building does not move, we say that it is in equilibrium (equilibrium is a Latin word meaning balance ). Laws of equilibrium were established by Isaac Newton. Simply put, these laws state that for each force applied to a building an equal force should oppose it.
Things you should discover…
Rigidity is a term often associated with triangles. Why? Are there three-dimensional shapes that should also be in a discussion of strength and rigidity? All structures are always in either tension or compression. Structures can only pull or push. What does it mean that a structure is in tension or compression?
- Get started on finding answers to your questions as given on the worksheets linked below. (These should be worked on in class AND as HOMEWORK!)
Design Engineer / Strength Engineer
Height Engineer / Journalist
Your research, homework, and interviews should help you gain some valuable knowledge about structures and strength.
Days 3, 4, 5, and 6: CONSTRUCTION and REPORT
1. Building your structures:
Once your group is equipped with more knowledge of structures and strength, you will be ready to create a structure. Using only white glue, 10 file folders and what you've learned about rigidity and strength from your experience, your experiments, and your research, you and your group are to create a structure that will hold the most weight, be very tall, or a combination of both. Can you cut the folders? YES...you can cut them and use white glue to glue them together. You can use paper clips and rubber bands to hold the folders together while they dry but they must be removed from the structure before testing.
You will be working in groups of 4 students. You will be given one file folder to explore first and then your group will be given 10 new ones for the project. This will ensure that all of the file folders are the same weight and size. Your group must plan well to make sure that you will be able to complete your structure in four class periods. All structures must be completed in class. You may not take your structure home to work on it. You’ll also be given a digital camera to document your building.
Be creative with your design. You will want to discuss this project with other people - students, parents, friends, and others - via conversations or e-mail.
2. Communicating and Evaluating your knowledge:
Your group can choose to either write a report or create a web page report to submit with your structure. The reports will be submitted both on disk and as a hard copy. The JOURNALIST is to coordinate this effort, not do it all. This report is to include:
o information about tension, compression, and rigidity. Make sure to explain if your structure will be under tension or compression or both and why. Talk about the rigidity of the geometrical shapes that you used in your design.
o the stress of natural disasters on structures and the structure's strength.
o at least one additional (important) piece of information from each set of research questions that you found while answering them.
o at least four helpful and interesting things that you learned from your interviews.
o reflections on things you've learned while building your structure. What things seemed to work? What didn't work? If you could have made changes, what would they be?
At the end of the report, list the people interviewed by the team. Also include a complete bibliography of resources used - both print materials and web pages.
Assign one member of the group to be the photographer. You will have the opportunity to use the digital camera to take pictures of your structure as you construct it. Photographs are to be used to document your design and building process as well as your final structure. A disk should be available during class to work on your report and to save photos. Some of these should be used either in your report or on your web page.
Unlike your structures, these reports/web pages probably will be completed outside of class. You and your groups can get together after school or communicate by phone or e-mail. At the end of the printed copies of the report attach the answers to all of your research questions and all of the completed interview worksheets.
Days 7 and 8 (if needed): Evaluation
Testing the structures:
- First, teams should submit each member's evaluation sheet, complete with his/her name and individual guesses for the amount of weight that the structures will hold.
2. The official measurer will measure the height of the structure in inches and record it on the evaluation sheet. Finally, you'll test your structure for strength. You must begin by placing a 25 lb. weight on your structure. Once a weight (2.5 lb - 45 lb. weights) has been placed on your structure, it cannot be removed and replaced with another....you should discuss some strategy. When any weight falls off of the structure or the height of the structure goes below 4 inches, the testing is complete. The weight is recorded at the last weight that was successfully placed and held by the structure for 5 seconds.
The most weight held by one of these structures so far has been 990 lbs. and it was 5.75 inches tall! The tallest structure was 11.5 inches and it held 360 pounds. If your structure is 5.75 inches tall and holds a minimum of 25 pounds, your group will be guaranteed a minimum of 10 points out of 20 for height and 10 points out of 20 for weight.
Communicating your Learning...
Finally, write a report or design a web page addressing the facts above. Include a complete list of Internet sites, bibliography of books and people interviewed during this project. Attached to the report (on disk and on paper) or web page (on disk with printout) should be the answers to the research questions, each of the completed interview sheets, and your answers to the reflective follow-up questions. It is recommended that all parts of the report be completed (except for the reflective follow-up questions) before the structures have been tested. The due date for the report will be given in class.
Resources
Internet Resources
PowerPoint Presentation Download / PowerPoint Presentation on the Web
The 25 Tallest Skyscrapers / Skyscraper Links
Resources in Print
· The Art of Construction: Projects and Principles for Beginning Engineers and Architects by Mario Salvadori. Chicago Review Press, 1990. ISBN 1-55652-080-8
· Structures: The Way Things are Built, by Nigel Hawkes, Macmillan, USA, 1993 ISBN # 0-02-000510-5
· Amazing Buildings by Philip Wilkinson, Doriling Kindersley, NewYork, 1993 ISBN # 1-56458-234-5
· Why Design? Activities and Projects from the National Building Museum by Anna Slafer and Kevin Cahill, Chicago Review Press, 1995 ISBN # 1-55652-249-5
Name ______
Tension/Compression Worksheet
All structures are always in either tension or compression. Structures can only pull or push.
Try this: Take a thin rubber band. Pull on it. You are putting the rubber band in tension and the rubber band becomes longer. When a part of a structure becomes longer it is in tension.
Try this: Take a thick sponge and push on it. When you push down on it, it is in compression and it becomes shorter. When a part of a structure becomes shorter it is in compression.
The amount of lengthening and shortening in a structure is usually so small that it is not possible to see it with the naked eye.
Consider a tent. The tent poles and the tent strings are part of the structure.
The tent poles would be in ______
The tent strings would be in ______
See if you can determine whether these are in tension ( t ) or in compression ( c ). Circle one
1. An elevator hangs from steel cables. Are the cables in tension or in compression? T C
2. Sit on a chair. Are the legs of the chair in tension or in compression? T C
3. A large pine tree has many branches. Is the trunk of the tree in tension or in compression? T C
4. Is a stone or marble in tension or in compression? T C
Try this: Find a partner. Put your hands on the shoulder of your partner and have him/her do the same. Move your feet away from each other one step at a time, forming an arch. As long as your feet are firmly planted on the floor your arch will remain in tact and you won’t fall. Why? Use this to answer question #5.
5. The stones of an arch bridge are pretty amazing when you think about it. Are they in tension or in compression? T C
Try this: Do this one with your partner also. Put your toes together and hold hands. Lean back without letting go of your hands and without moving your feet. What are you feeling with your arms? How does this relate to the next question?
6. A suspension bridge is supported by steel cables anchored on the ground and go over the top of the bridge towers.
a. Are the cables in tension or in compression? T C
b. Are the towers in tension or in compression? T C
7. Now it’s your turn. List at least 5 more things that are in compression and at least 5 more things that are in tension.
compression / tension1 / 1
2 / 2
3 / 3
4 / 4
5 / 5
6 / 6
7 / 7
8. Based on the way that your structure will be tested, must it be stronger in tension or compression and why?
9. Rigidity is a term often associated with triangles. Why?
Structure WebQuest – Design Engineer Questions
1. Animals and insects build structures for many reasons. A wonderful example of good engineering is that done by a honeybee. Draw an illustration of their structures and discuss the geometry that you see in its design. Why is this a good example worth investigating? What properties does it have that influence its strength?
2. Find other objects in nature to investigate. What did you find out about the strength of the design(s)?
3. When items are packed and/or shipped, they are often sent in cardboard boxes. What are the characteristics of corrugated cardboard that make it stronger than paperboard (like that in cereal boxes)? Is this corrugated cardboard stronger in some situations than in others? How does tension and compression affect it?
4. Find other objects in packing materials to investigate. What did you find out about the strength of the design(s)? Try this site.... http://www.mos.org/sln/SEM/gallery/guessit/8a.html
5. What 3-dimensional shapes did you explore and which ones seemed to be the strongest under tension? under compression?
6. What other questions do you want to find answers to while working on this project?
7. After working with the journalist in your group, get a copy of the interview questions and the name of one person to interview. You will need to complete an interview worksheet for the interview that you do and attach it to your research notes and turn it in with your report.
Structure WebQuest – Strength Engineer Questions
1. Name some natural disasters that can have devastating effects on structures. How do they affect structures?
2. What can be done in the construction of a structure to help in a structure's ability to experience little or no damage during natural disasters? (Finding out about the building codes in areas of the country that endure these disasters more often than others will be beneficial.)