Which Building Design Will Best Withstand an Earthquake?

Researched by Erik M.
2000-01

PURPOSE

The purpose of this experiment was to determine which building design will best withstand an earthquake. I became interested in this idea when I saw picture of a city that had been in an earthquake. I noticed that some buildings had collapsed and some hadn't. Then I wondered what made some buildings stand while others fell. The information gained from this experiment will help engineers build stronger, safer buildings that could resist an earthquake. This would cause less death in an earthquake.

HYPOTHESIS

My hypothesis was that a building with a base isolator would best withstand an earthquake. 

I base my hypothesis on a web site that can be found at http://www.archrecord.com/CONTEDUC/ARTICLES /200l.asp. The web site said "base isolation is most expensive, depending on the number of isolators required and type. "They also perform best," Friedman says." David Friedman is the president of Forell/Elssesser structural Engineers. 

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EXPERIMENT DESIGN

The constants in this study were:

  • The height of each building.
  • The motion the earthquake simulator simulates.
  • The width of each building.
  • All the buildings were tested indoors.
  • The device used to test each building.
The manipulated variable was the design of the building.

The responding variable was how long the building stood before it collapsed. 

To measure the responding variable I timed how many seconds the building stood with a stopwatch.

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MATERIALS
QUANTITY
ITEM DESCRIPTION
NA Clay
12 Rubber Bands
1 package Toothpicks
NA Aluminum Foil
1, 1 meter Foam Rubber Pipe Insulation
1 4mm thick, 60.5cm x121.5cm Pegboard
2 2cm thick 9cm x121cm Pine Boards
12 4D 1.5 inch Nails
1 Hammer
1 Stop Watch
1 Saw
1 roll Scotch Tape
3 sheets Printer Paper
NA Uncooked Spaghetti

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PROCEDURES

Make Buildings

1. Make 12, 24cm tall buildings with a perimeter of 24 cm. The buildings should be made out of toothpicks and the joints should be connected with clay. The buildings must have four stories that are 6cm each. It will be a 3-D building with four sides. 
2. On three of the buildings put cross-bracing. To do this take two pieces of uncooked spaghetti (broken to the right size) and cross them in an X shape. Put the X shape in the clay on each side of each story. 
3. On a different three buildings, put a shear core. To do this roll a sheet of printer paper into a cylinder that will fit inside the building. Tape it with scotch tape so it won't unroll. 
4. Place the shear cores upright in the center of each of the three buildings. Connect it from the sides with toothpicks poked through the paper. 
5. Cut two 6cm x 6cm squares out of aluminum foil.
6. Cut three 6cm x 6cm squares out of foam rubber pipe isolation. 
7. Take the three sheets of foam rubber pipe insulation and the two sheets of aluminum foil and stack them on top of each other in the order of rubber, foil, rubber, foil, rubber. Wrap two rubber bands around the stack horizontally, and two vertically. This is the base isolator.
8. Separate three buildings that don't have cross bracing or a shear core and set the base isolator by them. This is the base isolator group.
9. The remaining three buildings should be left normal as the control group.
10.Label each building with either cross bracing, shear core, base isolator, or control. Also put 1,2, or 3 on the label.
Make Earthquake Simulator
11.On the two pine boards saw (two) 42cm long, 9cm tall pieces, and saw (two) 32cm long, 9cm tall pieces.
12.Saw a 18.5cm x 26.5 rectangle out of pegboard.
13.With the boards from step 11 make a fence. 
14.Connect the fence with nails hammered through sides (two at each corner one on top of the other). 
15.Hammer four nails about 1cm into the top edge of the fence. There should be two nails on each of the 9cm x 42cm pieces about 6cm in from each of the corners. 
16.Take the pegboard rectangle and put a rubber band through the hole closest to each of the corners. 
17.Put a second rubber band through the two ends of the first rubber band.
18.Take the two ends of the second rubber bands and put them around the nails on the top edge of the fence. 
Test Buildings
19.Place clay on the bottom edge by the corners of the earthquake simulator so it doesn’t slip while shaking.
20.Connect the building you are testing to the center of the pegboard rectangle with clay.
21.Make the rectangle vibrate by pulling the rectangle back 2 cm and release. Do this constantly until the building falls over.
22.Have someone use a stopwatch to time how long the building stands for.
23.Repeat steps 19-21 to test all buildings. Since there is only one base isolator connect it to the building you are testing by poking the toothpicks on the bottom of the building through the base isolator. Then connect the base isolator to the pegboard rectangle with clay. When you are done testing the building with the base isolator switch it to a different building in the base isolator group. 
24.Record data on the data table, and record observations in experiment log.

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RESULTS

The original purpose of this experiment was to find which building design would best withstand an earthquake.

The results of the experiment were that the buildings with cross-bracing stood, on average, about 10 seconds longer than the buildings with the base isolator. The shear core buildings stood almost as long as the base isolator. All of the building designs helped the buildings because the control group did the worst. The cross-bracing buildings were very sturdy and didn’t rock. They fell only when the toothpicks slipped out of the clay.

See the table and graph.

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CONCLUSION

My hypothesis was that the building with the base isolator would best withstand an earthquake.
The results indicate that this hypothesis should be rejected, because the buildings with cross-bracing stood about 10 seconds longer than the buildings with the base isolator.

Because of the results of this experiment, I wonder if the building’s shape would effect how long it would stand in an earthquake. 

My findings should be useful to engineers, because they could build stronger, safer buildings that could withstand an earthquake. 

If I were to conduct this project again I would have used something other than clay to connect the joints in the buildings because the clay got softer after it had been worked with for a while. I would have connected the base isolator differently to the buildings because sometimes it slipped off. I would have also tried the design methods of shear walls, or moats. It would be interesting to visit a university or engineering firm that does real research in this area. I could then create a more realistic test setting.

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RESEARCH REPORT

INTRODUCTION

Earthquakes can destroy buildings and other structures. Unfortunately, this is a safety hazard to humans. Buildings that could withstand an earthquake would cause much less injury and death in an earthquake. 

Earthquakes

Earthquakes in General
An earthquake happens when "Stresses in the earth cause large blocks of rock along a fault to strain or bend. When the stress on the rock becomes great enough, the rock breaks and snaps into a new position, causing the shaking of a earthquake." From The World Book Encyclopedia, volume E, page 33, by Karen C. MacNally. Earthquakes cause tsunamis, fires, chemical spills, landslides, and damage to buildings. Tsunamis are like huge tidal waves. Underwater earthquakes cause them. Tsunamis are dangerous because they flood coastlines and can be up to 100 feet tall.
Seismic Waves
The energy or vibrations that travel through the earth in an earthquake are called seismic waves. P (primary) waves also known as body waves are the fastest and cause the most damage. There are two kinds of P waves, compressional waves and shear waves. Compressional waves make compressions and expansions in earth. Shear waves move the earth in a side to side motion. S (secondary) waves also known as surface waves are slower and cause less damage than P waves. There are two types of S waves, the Love wave and the Raleigh wave. Love waves are like shear waves, but they travel horizontally through the earth. Raleigh waves move the earth in a wave motion.
Measuring Earthquakes
It is important to measure earthquakes so in the future we can predict when and where an earthquake will happen. Every year on average there are about 8,000 minor earthquakes (only 1,100 can be felt by humans), 40 moderate, and 1 large about every two years. There are two systems used to measure earthquakes, the Richter Scale and the Modified Mercalli System. The Richter Scale is used to measure the amount of energy an earthquake puts out. It is measured in numbers from 0 to about 10, but it can go beyond 10. The Modified Mercalli System measures the amount of damage an earthquake causes. It is measured in Roman numerals from I-XII. A seismograph is an instrument used to record vibrations in the earth.
Geological Terms
There are many terms and theories that scientists have about earthquakes. Scientists have a theory called plate tectonics. Their theory is that the earth's crust is broken into about 30 plates. These plates are moving on the mantle. When they hit it causes stress on the rock. The spot where the rock is stressed is called a fault. The San Andreas Fault is about 600 miles long. It runs through California. Many earthquakes occur along this fault. The focus of an earthquake is where the rock first breaks, and the epicenter is the surface directly above the focus. Aftershocks are smaller quakes after the main quake.

Earthquake Proofing Buildings

Earthquake Proof Methods
Engineers have developed many ways to try and protect buildings in an earthquake. One of the methods is base isolation. A base isolator is put at the base of a building between the foundation and the actual building. The base isolator is made from layers of steel and synthetic rubber. The base isolator absorbs some of the vibrations. Another method is cross bracing. Cross-bracing reinforces the walls of a building. Cross-bracing is when there are diagonal steel beams in the framework that make an "X" shape. A shear core or shear walls helps to resist the rocking in an earthquake. Shear walls are made out of concrete with steel beams through them. A shear core is the same thing except it is at the center of the building, usually around an elevator or staircase. A moat around the building will let the building sway. Bolting the building to the ground will also help.
Framework
The framework of the building is important too. Flexible framework is better than stiff framework because it will just bend in the shaking of an earthquake. If the building has stiff framework then it would break and the building would collapse.
Places to Build
There are good places to build and there are bad places to build a structure. Do not build in flood plains or areas where a landslide could happen. The best thing to do is build away from fault zones. Also build on strong rock not on sand or mud.
Safety
To stay safe in an earthquake there are certain things you should do. If you are indoors go under a table, desk, or bed. Don't go in an elevator or staircase, and if you can, get outside. If you are outdoors stay away from buildings and tall objects such as trees or street lights. If you live in an area where earthquakes happen often, bolt heavy objects in your house to the floor.

SUMMARY

Earthquakes are one of the most deadly forces of nature. Many people die or get injured in earthquakes every year. In the future earthquakes might be predicted weeks in advance and people could get safely out of the area. Scientists are still studying seismic waves, faults and the theory of plate tectonics. Engineers could build stronger, safer buildings that could resist an earthquake if they study which methods of building protection work the best. 

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BIBLIOGRAPHY
  • Anderson, John, "San Andreas Fault," The World Book Encyclopedia, 1999, vol. E, pp. 83-84
  • Cloos, Mark, "Ring of Fire," The World Book Encyclopedia,  1999,  vol. Q and R, pp. 342
  • "Earthquake Resistant Buildings," [Online] Available http://www.irrdb.org/prods/earthq.htm , November 21, 2000
  • "Earthquake," Compton’s, 1998
  • "Earthquake," The World Book Encyclopedia, 1997, The Planet Earth pp. 74-75
  • "Earthquakes," Encarta, 2001
  • "General Questions and Answers about Earthquakes," [Online] Available http://www.seis.utah.edu/qfacts/genfaq.shtml#gqb , November 1, 2000
  • MacNally, Karen.   "Earthquake," The World Book Encyclopedia, 1998, Vol. E, Pp. 33-39
  • "Measuring Earthquakes," [Online] Available http://www.riverdeep.net/6/owa/page?p=events.equake-measure , November 1, 2000
  • Merke, William,  "Earthquake," Groliers, 1998
  • Merriam-Webster’s Collegiate Dictionary Tenth Edition, Springfield, Massachusetts, Merriam-Webster Incorporated, 1999, pp. 362
  • "Seismic Systems that Stand Up to Nature," [Online] Available http://www.archrecord.com/CONTEDUC/ARTICLES/2001.lasp. November 14, 2000
  • Simon, Symour. Earthquakes. New York: Morrow Junior Books, 1991.

ACKNOWLEDGMENTS

I would like to thank the following people who made my science project better:

  •  My Mom, for timing how long the buildings stood for with a stopwatch while I worked the earthquake simulator. She also held the boards while I sawed them, and she drove me to the stores I needed to go to.
  • Jordan P., for telling me how to avoid mistakes that happened to him when doing a similar project.
  • My Dad, for holding some of the boards while I sawed them.
  • Mr. Newkirk, for staying after school so I could finish my project.
  • Mrs. Pasckvale, for staying after school and answering my questions.


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