This Is My Science Fair
Background Information
Buildings are affected by forces during earthquakes, by wind, and by snow. Over time, if the building starts to lean, gravity will also take its toll.
The Development of Buildings
Rectangles
Rectangle structures are susceptible to shear force. The walls can push out or lean. See the examples of a 14th century house in England and a house that was in a San Francisco earthquake.
Triangles
If you put a cross brace in a square, it becomes two triangles.
Now we have a rigid structure that does not deform easily, e.g. under a snow load. Another example is that my grandparents put cross braces in the fences near the gates. See force diagram.
Roof Trusses
Engineers learned to use the strength of triangles in square buildings for the roof… but not in the walls. See diagram.
Domes
So… what about a building that’s made out of only triangles? Buckminster Fuller invented geodesic domes in the 1960s. These are amazing in many ways. They resist shear force, earthquakes, and gravity.
Question
What makes a building strong?
Hypothesis
Triangles are the strongest shape, so I believe that a geodesic dome will be better than other structures, because a geodesic dome is made up of many triangles. This makes it better because, there are more supports to take the force that is being applied.
Procedure
1. Make multiple structures with squares and triangles. Try different combinations of triangles and squares.
2. Apply force by pulling with spring weight, and see how much it flexes (take photos with some sort of camera so you can exactly how far it goes before flying apart). Put grid paper behind with a visible start line so you can see exactly how far it flexes.
3. Build new structures, or you can repair the old ones, depending on how worn out the Zome sticks and balls are.
4. Repeat tests.
5. Compare the results.
Materials and Equipment
Ø Zome Creation Kit (plastic sticks and connecter balls).
Ø Spring scale
Ø Graph paper
Ø Weighing scale
Ø IPod (for taking photos to get accurate measurement).
Ø Computer
Ø Cats
Data Analysis
We collected two kinds of data: the inches that the structure sheared, and the force that we put on it.
As you can see from the data table:
Ø The simple cube did the worst (meaning that it leaned the most the under the shear force that we applied.)
Ø The A-frame did very well. The A-frame sheared less than the pyramid but it did not take as much force.
Ø Second last is the pyramid. It took the most force, but it did shear more than the A frame or the geodesic dome.
Ø Finally, the geodesic dome, was the best we had, in fact it was actually better than the materials. In the photo you can see that the bar itself was bending but the dome it self, stayed solid.
Data Table 1:
Measured Shear Forces and Distortions
Test
|
1
|
2
|
3
|
4
|
5
|
Cube
force applied
|
4 lb.
1.8 kg
|
5.5 lb.
2.5 kg
|
6 lb.
2.7 kg
|
5.5 lb.
2.5 kg
|
4.5 lb.
2 kg
|
distance sheared
|
3 in.
75 mm
|
3 in.
75 mm
|
3 in.
75 mm
|
3.5 in.
88 mm
|
3 in.
75 mm
|
A Frame
|
5 lb.
2.3 kg
|
6 lb.
2.7 kg
|
8 lb.
3.6 kg
|
3 lb.
1.4 kg
|
6.5 lb.
3 kg
|
distance sheared
|
0.25in.
6 mm
|
0.25in.
6 mm
|
0.25in.
6 mm
|
0 in.
0 mm
|
0.25in.
6 mm
|
Pyramid
|
3 lb.
1.7 kg
|
10 lb.
4.5 kg
|
11 lb.
5 kg
|
8 lb.
3.6 kg
|
5.5 lb.
2.5 kg
|
distance sheared
|
0.5 in.
13 mm
|
0.25in.
6 mm
|
0.25in.
6 mm
|
0.5 in.
13 mm
|
0 in.
0 mm
|
Geodesic
Dome
|
6.5 lb.
2.9 kg
|
8 lb.
3.6 kg
|
8.5 lb.
3.9 kg
|
6 lb.
2.7 kg
|
7 lb.
3.2 kg
|
distance sheared
|
0 in.
0 mm
|
0 in.
0 mm
|
0 in.
0 mm
|
0 in.
0 mm
|
0 in.
0 mm
|
Each square on the grid paper = 1 in.
Pounds = lb. Kilograms = kg
Sample Calculations
This is how I got the averages of the measurements.
Example 1
Shear force, measured in pounds by our spring scale for the cube
4 + 5.5 + 6 + 5.5 + 4.5 = 25.5 lb.
I divided by five because I did my test five times.
25.5 ÷ 5 = 5.1 lb.
Example 2
Distance sheared, measured in inches by our grid paper and photos for the cube.
3 + 3 + 3 + 3.5 + 3 = 15.5
15.5 ÷ 5 = 3.1
Data Table 2:
Average Shear Forces and Distortions
Structures
|
Pounds/kg
|
inches/mm
|
geodesic
dome
|
7.2 lb. 3.26 kg
|
0 in. 0 mm
|
pyramid
|
8.1 lb. 3.5 kg
|
0.3 in. 5 mm
|
cube
|
5.1 lb. 2.8 kg
|
3.1 in. 77.6 mm
|
A frame
|
5.7 lb. 2.6 kg
|
0.2 in. 4.8 mm
|
Sources of error
Here are some potential sources of error in this experiment.
How the hand was holding down the structures:
Ø It was important to hold it firmly and in the same way each time, and make sure the hand was not obstructing the shearing (leaning) ability of the structure.
Wear and tear:
Ø The Zome sticks could have been worn out, since they are a couple years old. Sometimes the joints popped way too soon. We replaced the worn out parts, rebuilt the structures for each trial, and repeated the data several times to lessen this effect.
Ø For the spring scale, the spring might have worn out a bit. But this is unlikely, because we bought it brand new, and it’s a nice one made in Germany.
Misalignment:
Ø It is important to line the structure up at the starting line (the blue line on the wall) each time.
Variables
Manipulated
Ø Design of structures
Responding
Ø Inches sheared
Ø Amount of force applied before structures shatter
Controlled
Ø Same method of holding
Ø Same method of pulling
Ø Same person to do those tasks.
Ø Rebuilding the structure each time
Ø Same material
Ø Start position
Ø Same data reader
Conclusion
The geodesic dome moved the least of all the structures, but it did not take as much force. I believe this because of the failure of our materials.
Bibliography
(http://www.shelter-systems.com/relieftents/)
(http://www.domeguys.com/domes/adventure-domes/)
(http://www.domeguys.com)
Acknowledgments
The first person I want to thank is my mom. She was the person who held down and pulled while I took the photos, she also helped me write my science fair, but most important is that she motivated me when I felt like throwing the experiment out the door. I would also like to thank my friend Henry, who helped me to do a little research.
Areas of further research (things I would try next time)
Ø Could put weights on the top (to test snow load)
Ø Test more designs
Ø Buy brand new Zomes
Ø One thing I could try is gluing together the structures. But I believe this would bring up many problems.
Application to Society
This would be able to be used in society by using these as cheep structures because it takes 1/3 of the amount of lumber used to make a classic house.
Also in disaster situations domes are used as shelters, because they are lightweight because they only take up 1/3 of the materials, and they are very easy to put up (I know this because I have helped build 4 of them).
Another use would also be that they can be built in developing countries, where they don’t have as much money (because it has 1/3 of the materials, sorry that is the third time I have mentioned that, BUT it is so awesome).
At last, one of the most important reasons is that they’re incredibly strong. They have been recorded to survive a 7.1 on the Richter scale,
Why I chose to do this experiment
We used to have a geodesic dome as a garage. One time a really strong wind came and blew it 500 metres across a lake and the only damage it had was one beam broken. We were able to hook it up to our car and drag it back no problem. We nailed another board over the broken one and the building worked perfectly again. (We sand-bagged it down this time!)
This got me interested into geodesic domes. I also wanted to know what made a good earthquake structure, and I found that geodesic domes are really good in earthquakes. Then the Science Faire came up, and I thought that it would make a good project.
I researched (with a friend) how they counter earthquakes. I found that they usually have a base that is attached to the rest of the building. But it is attached so the floor moves but the rest doesn’t. Another earthquake strategy is that they have made a skyscraper with a giant pendant that moves in the opposite direction of the earthquake. These strategies are similar to how the geodesic dome works, because they rely on buildings being to flex and move, which geodesic domes are able to do.
Note from Yarrow’s mom:
Certain adults questioned whether Yarrow actually has experience of domes. Here are 4 that he has helped build:
1. A dome that we used as a greenhouse and then a garage. Connector plates: Stromberg's chickens. Cross pieces: 2 x 4s. Cover: polythene. Not only did he help to build it but he got to experience it in wind, rain, snow, sun, and flying across a lake (which broke it, so then we got the fun of fixing it and it worked fine). He got to experience how warm it was in the summer, and more startling, in the winter! WAY more information than he can fit in one science fair.
2. A Pacific Domes professional home dome that we used for a while as a spare room of the tiny cheap broken farmhouse that we used to live in. Major sound and thermodynamic research occurred in that one.
3. A festival dome that we built for Beakerhead, for the Storytellers tent. You can find a photo in the Herald about it. We built it again with Stromberg's chickens starplates but used 2 x 2s this time and sewed an absolutely gorgeous amazing cover from curtains we got from the Goodwill shop. (Beakerhead helped sponsor it).
4. We saw a man erecting a steel-framed geodesic dome by himself at a festival, so we stopped to help him, though he told us he was completely capable of doing it alone and had done so many times. But we stopped to help because we were interested.
