Which Building Shape Best Withstands an Earthquake?

Researched by Tim S.
2001-02




PURPOSE

The purpose of this experiment was to determine which building shape would best withstand an earthquake.

I became interested in this idea when an earthquake occurred in the state of Washington.

The information gained from this experiment could be used by building designers and engineers to know which building shape to build in an earthquake zone versus a non-earthquake zone.



HYPOTHESIS

My hypothesis is that the dome shaped building would withstand an earthquake for the longest.

I base my hypothesis on World Bookís Young Scientistís Encyclopedia on Construction and Machines, which states, "It is most useful because it holds itself up."




 EXPERIMENT DESIGN

The constants in this study were:

  • The magnitude of the simulated earthquake
  • The materials used to build each building
  • The earthquake simulator used
  • The distance each toothpick is stuck into the clay
  • The diameter of each clay ball
  • The placement of each building on the earthquake simulator
The manipulated variable was the shape of the building.
 

The responding variable was the time it took for the different buildings to collapse.
 

To measure the responding variable I will measure the time the building stayed up before collapsing in seconds. 



MATERIALS
QUANTITY ITEM DESCRIPTION
1 pack  Modeling Clay
1 pack   Toothpicks
 Stopwatch
Size 33 Rubber Bands
12  4D 3.8 cm Nails
Hammer
2 41 cm by 7 cm Pine Board
25 cm Peg Board
 35 cm by 7 cm Pine Board



 PROCEDURES

Build the Earthquake Simulator

1. Tie a rubber band to each corner of the pegboard by putting it part way down the hole and bringing it back through the loop in the rubber band. Each rubber band should be in the closest hole to the corner. Make sure it is pulled tight.
2. Connect these 4 pieces of wood together by putting two nails into each end of the wood. Two should be in each corner with one directly above the other. 
3. Using the hammer put four nails on top of the fir wood boards, with two on each side, cm from each corner. These should be about 1 cm deep. 
4. Attach the rubber bands and the pegboard together by looping the rubber bands onto each nail.

Construct the Buildings

 Cube
5. Make a square with the toothpicks by connecting them with 2 cm diameter spheres of modeling clay. 
5. Put a toothpick in the top of each ball. They should be forming a 90° angle with the toothpicks on the bottom row.
7. Repeat step 5. Then place this square on top of the toothpicks that are sticking up. This is now a cube.
Tall Rectangle
8. Repeat steps 5-7 two more times.
9. Make three more cubes using steps 5-7. 
10. Now put toothpicks in the top of each clay ball on the four higher ones as shown in step 6.
11. Now make squares and place them on top of these toothpicks. 
Pyramid
12. Repeat step 5. 
13. Put one toothpick in each clay ball so that they can be connected at the top with another clay ball.
14. Connect each toothpick at the top with a clay ball. Each side should be a triangle. 
Dome
15. Make a hexagon with toothpicks and connect them with clay. 
16. Make triangles coming up out of every other 2 clay balls. 
17. Connect the top of the triangles so that they form another triangle on top.
18. Repeat steps15-17 twice.

Conducting the Experiment

19. Place the first cube in the center of the earthquake simulator. 
20. Pull the peg-board back to the edge of the 35 cm.
21. When you let go, begin the stopwatch.
22. Continue pulling back the peg-board until the building collapses. When it collapses stop the stop watch. If the building does not collapse after 5 minutes, stop the stopwatch.
23. Record the time in a data table.
24. Repeat steps 19-23 for each of the cubes.
25. Repeat steps 19-23 for all of the tall rectangles.
26. Repeat steps 19-23 for all of the pyramids.
27. Repeat steps 19-23 for all of the domes.



  RESULTS

The original purpose of this experiment was to determine which building shape best withstands an earthquake.

The results of the experiment were that the dome and the pyramid were able to withstand the earthquake the longest. They never fell after 300 seconds. The cube stayed standing for about seven seconds. The tall rectangle did not stand over a second in any of the three trials.

See the table and graph below.

View my Data and Graphs



 CONCLUSION

My hypothesis was that the dome would withstand an earthquake for the longest.

The results indicate that this hypothesis should be accepted. 

Because of the results of this experiment, I wonder if the taller that a tall rectangular building is, the less amount of time that it takes before it collapses in an earthquake.

If I were to conduct this project again I would make my clay balls smaller so that the dome and the pyramid would eventually fall over. Also I would build my earthquake simulator larger so that I could pull the pegboard back farther and increase the magnitude of the "earthquake". I would also do something to alter the design so that the tall rectangle and cube would better withstand the simulated earthquake. I would also do more trials.



 
 

RESEARCH REPORT

INTRODUCTION

Safety is important to everyone. Earthquakes destroy buildings and the homes of people. They cause tsunamis, fires, chemical spills, landslides, and several other disasters. Earthquakes are very dangerous. Buildings must be earthquake resistant so that our lives will be in the least danger possible.

EARTHQUAKES

According to World Book Encyclopedia, an earthquake is, "A shaking of the ground caused by the sudden breaking and shifting of the earthís rocky outer shell." Earthquakes can be very powerful or, they can be so small that they canít be detected by a human being. Large earthquakes are usually followed by smaller ones called aftershocks. Aftershocks are usually a lot smaller than the main earthquake.

Most scientists agree with a theory called plate tectonics. They believe that several plates are floating on the mantle of the earth. When these plates collide, it causes stress and an earthquake takes place.

Harry Fielding Reid studied the San Andreas Fault and formed a new theory. He theorized that the cause of an earthquake was not close to the focus, or center of the earthquake. He said that forces that are very distant build up over hundreds of years. When the earth cannot resist this force it gives way. This theory is called the "elastic rebound theory." 

SEISMIC WAVES

"Body" waves usually cause the most seismic damage.  There are two types of body waves.  There are the compressional waves and shear waves. Compressional waves are when the rock is compressed and expanded. Shear waves are when the rock shakes back and forth. "Surface" waves are long and slow. The two kinds of surface waves are Love waves and Rayleigh waves. Love waves have a side-to-side movement. Rayleigh waves roll like the waves of an ocean. 

MEASURING EARTHQUAKES

To determine the strength and location of an earthquake, scientists use a seismograph. A seismograph is a machine that has little sensors called seismometers. These detect the shakings of the ground that are sometimes very far away. They can detect movements as little as a billionth of a meter. Scientists called seismologists measure the ground movement in three directions: up-down, north-south, and east-west. The record of a wave is called a seismogram. 

The intensity of an earthquake is usually measured on a 12-point scale called the Modified Mercalli Scale. The magnitude of an earthquake is measured on the Richterís scale. This is a measure of the strength of its source, or focus.  On this scale, every increase of one number means that the earthquake has 32 times more energy released by the quake. A seven on the Richterís scale is severe, while an eight is devastating. A two can only be detected by a seismometer. Another scale is called the Moment Magnitude Scale. This is the most accurate of the scales. It measures the total damage done by an earthquake. 

EARTHQUAKE PROOFING BUILDINGS

Geologists look for and do research on safe places to build. They say that the best places to build structures are away from an earthquake zone. Also it is best not to build in mud or soft dirt. This could cause a building to sink quickly. 

Architects and engineers have also developed several building types. They include cross bracing, shear core, base insulator, and shear wall buildings. Cross bracing has braces in each side and on each level, which forms a cross. This reinforces the walls of a building. Shear core buildings have a square core in the middle that runs from top to bottom. This helps to resist the rocking that an earthquake has. The base insulator has an insulator built between the foundation and the walls of a building. The insulator is made from steel and synthetic rubber. Moats that are built around a building allow a building to sway. Flexible framework also helps the building to sway. 

SAFETY

Safety precautions are very important during an earthquake. People should not go outside until the shaking is over. They should crouch under a desk or crawl under a bed or chair. If you are not able to get under one of these, you should stand under a doorway. 

SUMMARY

Earthquakes are a major natural disaster. Although they almost never kill people directly, they are very dangerous. Scientists are studying seismic waves in hope of finding a way to predict them in advance. Engineers are also trying to determine which building designs are the best in earthquake zones.

BIBLIOGRAPHY

"Earthquake." Microsoft Encarta Encyclopedia Deluxe. 2001.

"Earthquakes." The World Book Encyclopedia of Science, The Planet Earth. 1997.

"Earthquake." Websterís Third New International Dictionary Unabridged. 

"General Quake Information." November 21, 2001. http://quak.wr.usgs.gov/info/basics.html

McNally, Karen C. "Earthquake." The World Book Encyclopedia.

Simon, Seymour. Earthquakes. New York: Morrow Junior Books, 1991.

"The Strength of a Dome." World Bookís Young Scientist. Volume 9. 1997.

"Understanding Earthquakes." November 12, 2001. 
http://www.crustal.ucsb.edu/ics/understanding/
 


ACKNOWLEDGEMENTS

This science project could not have been completed without the help and advice given to me by several people. I would like to thank each one of them for their help.
 

  •  My dad helped me build the earthquake simulator by cutting the wood to the right sizes with the electric saw. He also gave me several pieces of advice for building the buildings.
  •  My mom was very supportive and drove me to before school work times. She also picked me up after the after school classes.
  •  My friend Erik for giving me the wood to build my earthquake simulator. He also was able to give me advice on my project since he did one similar last year.
  • Mrs. Helms gave me advice and encouragement when I was having trouble with my project.
  • Mr. Newkirk for giving advice when I was struggling and on my journal and report and my project board.

 
 


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