|
|
|
1999 Curriculum Projects Home Page
Project Goals:It is the energy from earthquakes that put human beings and human structures in danger. Energy is transmitted through the Earth in the form of waves. My project’s goal is to teach 8th grade curriculum in an interesting and relevant way to students. Twin Falls Curriculum and Science Standards include knowledge of energy in the form of waves. Physic books do address waves and commonly have a small reference to seismic waves. Students are very interested in disasters as can be attested by the deluge of recent movies. My plan was to ‘grab’ and direct their attention through connecting with real life (as in observing buildings being built around them and where they live and shop) to basic science principles. Lessons were planned around active ‘hands on’ activities. The lessons were great fun! The students were actively engaged and fascinated with my ‘teacher’ prepared models. My principal and vice-principal came to participate and observe due to positive comments from parents and students. A father of a student, and construction worker, called to share how thrilled he was that his daughter was asking questions about moment resistant frames and how the walls were connected to the foundation, etc. Best of all, there was quality learning accomplished and awareness generated about what is involved in being earthquake prepared.
|
|
Standards Connection: Twin Falls District Science Curriculum Standards: Physical Science Standard 12: Understands motion and the principles that explain it. *8TH Grade Learning Objectives: Knows that vibrations move through systems as waves. Understands vibration in terms of amplitude and frequency. Standard 14: Understand the nature of scientific knowledge. Standard 15: Understands the nature of scientific inquiry. |
Materials:
Metal Slinkies
Selected Earthquake Videos (Nature’s Fury)
Meter Sticks
Clamps
6 Wood Pieces (24 “ X 8”)
18 Metal Rods of 3 heights
18 Small Wood Squares
Drill
Stopwatches
Frequency Lab Worksheet
Discover students’
background of the properties of amplitude, frequency, and resonance.
Student or teacher lab:
1. Carefully clamp a meter stick to the edge of table so that one end
sticks out over the end.
* Gently tap the meter stick to make it vibrate.
* Watch how the stick moves up and down.
2. Now loosen the clamps and increase the length that sticks out.
* Watch again how the stick moves up and down.
* How did the frequency of this up and down movement
change?
3. Manipulate the frequency by increasing and decreasing the length of the
stick.
* Observe the frequency of the up and down movement.
* Record your observations.
* (The frequency is the characteristic of the motion.
The frequency of a motion is directly related to the energy of vibrations.
Frequency is the number of waves produced in a set time.)
4. Inform students that when they are listening to their favorite radio
station (KSKI 103.7 MHz (103,700,000 Hz), the electrons in the radio
antenna are vibrating at the same frequency- 103,700,000 vibrations per
second.
* Hertz (Hz) is the unit of measurement for frequency
as recorded in cycles per second.
* MHz is a frequency of 1,000,000 cycles per second.
1. Drill a small hole in boards. Insert rods of different heights into
the boards.
2. Drill holes in the small squares. Insert these squares on the end of
the rods.
| Direct students’ attention to teacher model. Ask the students to predict which rod (short, medium, or tall) will vibrate or oscillate the most when a sideways force is applied to the base. (Most students will choose the tallest rod). |
3. Move the model so that the shortest or medium height
rod vibrates the most.
* Ask the students to predict again.
* With practice, make each of the rods vibrate.
* Invite discussion.
4. Relate the blocks and rods to buildings of different heights that would
be found in a city during an earthquake.
* Inform students that in the 1985 earthquake in Mexico
City, the ground shaking resonated with natural frequencies of 8 to 10
story buildings. The effect was extreme damage to medium-height buildings
that had the same frequency as the ground shaking and resonated with it.
Higher and lower buildings received minor damage.
[Top of Page]
| (Concept checks: Earthquakes cause seismic waves that produce vibrations in materials with different frequencies. Every object has a natural rate of vibration that scientists call its natural frequency. The natural frequency of a building depends on its physical characteristics, including the design and the building materials. Resonance occurs when a vibrating object causes another object to vibrate at one of its resonant frequencies.) |
1. Divide students into groups of four.
2. Instruct students that they will have jobs:
* timekeeper-using stopwatch),
* recorder,
* starter,
* and counter.
Groups will take turns and repeat experiment four times for more accurate
data. (Refer to Lab worksheet).
3. Model the correct way to count a wavelength by holding the base
stationary.
* Pull the wooden block out several centimeters to the
side and then release it.
* As the rod swings back and forth, use a stopwatch to
measure the time for 10 complete swings.
* Record.
4. Practice and then repeat measurement four times.
* Calculate the average of these four times.
* Now calculate the natural frequency of the number by
dividing 10 cycles by the average time.
* (Make sure students are dividing
INTO ten, rather than by ten!)
* Record.
* Repeat this procedure for the other two.
5. Measure the height of each rod assembly from the base to the top and
record.
6. Plot height versus natural frequency on the graph.
* (Students should come up with a hyperbola, a curve
representing an inverse relationship in which, as the height of the
structure increases the natural frequency decreases.)
7. Ask students what determines the damage in an earthquake. (Lead
students to understand that amount of damage correlates to the population
density.
* To help students understand the relationship of
frequency and resonance, talk about pushing someone in a swing.
* The person pushes a little at a time, for
a period of time, and soon the swing will go very high without a big push.
Each small push is at the right frequency. In an
earthquake, a building may vibrate with great amplitude without a big
earthquake vibration because the smaller vibrations came at that
structure’s natural frequency.)
8. Share and discuss each group’s data.
* Again point out the connection between the
experimental results and the way real buildings resonate. Other things
being the same or equal, taller buildings have lower natural frequencies
than short buildings.
| Resonance is a buildup of amplitude in a system that occurs when the frequency of an applied vibrating force is close to the natural frequency. Ground shaking in an earthquake may be at the same frequency as the natural frequency of the building. Each vibration in the ground may come at or dangerously close to the frequency of the building. |
9. Ask students to speculate what would happen if buildings of two
different heights, standing next to each other, resonate from an
earthquake.
* Wiggle the model and let students observe how
buildings can collide into each other.
10. Show students actual video footage from earthquakes.
* Discuss what they are seeing with the
information they have acquired.
* Ask students for ideas on how to reduce
resonance in a building.
* This would be an excellent opportunity to have
a structural engineer visit the classroom. My friend, who is a structural
engineer, commented on the different approach of different cultures.
Japan, which is constantly bombarded by earthquakes, builds to incorporate
the movement of the waves. Western cultures, like the United States, brace
against the waves.
* Place wheels under the wooden assembly and then
shake the table it is on.
* Discuss what happens. (Compare the model to an
inverted pendulum.)
11. Instruct students to write in their science journals about what
structural elements could be added to reduce vibrations in a building.
* Write about what presently can be done, and
what possibilities with fast growing technology, could be accomplished in
the future.
* Remind students to deal with ever increasing
population density.
|
Standards Connection: Twin Falls District Science Curriculum Standards: Physical Science. Standard 12: Understands motion and the principles that explain it. *8TH Grade Learning Objectives: Knows that vibrations move through systems as waves. Understands vibration in terms of amplitude and frequency. Standard 14: Understand the nature of scientific knowledge. Standard 15: Understands the nature of scientific inquiry. |
1. Students will recognize some of building
structural systems: shear walls, moment resistant frames, and braced
frames.
2. Students will observe how added structural elements strengthen a model
wall to withstand sideways forces or shaking.
3. Students will recognize that Idaho is ranked fifth highest in the
nation for earthquake risk and possible ramifications.
Materials for Model Wall:
21 Jumbo Popsicle Sticks (per wall)
Drill
Wood Base (18” X 2”)
16 machine bolts
16 machine screw nuts (32 washers)
Small paper clamps
2 pieces of string (12”)
1 piece of cardboard (slightly smaller than 6”sq)
8 or more, small paper clamps
Small squares of cardboard for bracing
EERI CD of Northridge Earthquake
Teacher
assembles model wall. Follow directions below:
Experiment with tightening bolts until they are just tight enough for the
wall to stand up alone. (Popsicle sticks are fragile. Drill extras
for replacements.)
Explain to students that this demonstration will show how structural elements of a wall carry forces. Draw pictures and discuss with class the basic structural systems: shear walls, braced frames, and moment resistant or rigid frames.
| [Shear walls are solid walls designed to carry the force to the vertical resistance elements (shear walls or frames). In a simple building with shear walls at each end, ground motion enters the building and moves the floor diaphragms. This movement is carried by the shear walls and transmitted back down through the building to the foundation. Braced frames act in the same manner as shear walls, but may not carry as much load depending on their design. Bracing generally takes the form of steel rolled sections (I-beams), circular bar sections, or tubes. Rigid frames rely on the capacity of joints to carry loads from columns to beams. Because these joints are highly stressed during movement, details of their construction are important. Architecturally, rigid frames allow more freedom in designs by allowing space for opening, exterior walls, partitions, and ceilings. Moment resistant frames require special construction and detailing and therefore, are more expensive that shear walls or braced frames.] FEMA 99, October 1990 |
Discuss buildings students are familiar with and may have seen in the building stages. This is an excellent time to invite in a contractor or builder to discuss advantages and costs of these types of structures.
1.
Show students the models and explain that it represents part of the frame
of a building.
* Ask what holds the wall up.
* Ask students to predict what will happen if the teacher pushes the base
of the wall, simulating S waves during an earthquake.
2.
When model is pushed just hard enough, the model should collapse at the
first floor only. Make sure to practice and check screws for equal
pressure.
* Ask students why the other floors didn’t collapse. (The first floor
collapsed because it was not strong enough to transfer enough horizontal
force to move the upper stories. It couldn’t transfer the shaking to
upper stories.)
3.
Exert different sideways forces and make the second and third stories
collapse.
* Explain that pushing the base of the model is equivalent to applying
force horizontally to the upper stories.
* Ask students how they could add structural elements to create a path for
the force or load to follow to the ground when strong forces act upon the
structure.
* Try different strategies suggested by students. Point out that by using
string, cardboard, and clamps they are adding a shear wall, diagonal
bracing, (I compared the model to a school with the first floor occupied
by seventh graders, middle floor eighth graders, and top floor ninth
graders. It made it more exciting when the floors failed.)
4.
If more models have been made, divide students into groups and have them
experiment and discover strategies.
* When students discover a setup that works, diagram it and sketch the
line of force using arrows.
* Test the force or load paths by removing elements not in the path to see
if the building will stand up to a secondary wave.
| Geological and seismological studies show that earthquakes are likely to happen in any of several active zones in Idaho and adjacent states. Idaho is ranked fifth highest in the nation for earthquake risk. The 1991 Uniform Building Code, a nationwide industry standard, sets construction standards for different seismic zones in the nation. UBC seismic zone rankings for Idaho are among the highest in the nation. When buildings are built to these standards, they have a better chance to withstand earthquakes. Earthquake Risk in Idaho, Othberg and Breckenridge, IBDS. |
5.
Discuss with students the significance of the above statement.
* Ask if they think that higher standards should be mandated for schools,
hospitals, retirement homes, etc.
* Enter in the cost impact.
* Walk around the school and note visible structural supports.
* Assist students in evaluating how well the school would withstand an
earthquake.
* Assign students to go to large stores or buildings and determine what
impact sideways forces (S waves) would have to shoppers in the stores.
* Costco has items stacked on very high shelves with no visible means of
restraint.
* Continue discussion after students report their findings.
* Show examples of buildings in earthquakes where structures cracked or
partially collapsed.
* Discuss their perceptions of why and what could have been done as a
preventative measure.
|
Standards Connection:
Twin Falls District Science Curriculum Standards: Physical
Science. Standard 12: Understands motion and the principles that explain it. *8TH Grade Learning Objectives: Knows that vibrations move through systems as waves. Understands vibration in terms of amplitude and frequency. Standard 14: Understand the nature of scientific knowledge. Standard 15: Understands the nature of scientific inquiry. |
1. Students will construct a model of a shake table to test their building’s seismic survivability.
2. Students will design a structure that will carry both vertical and horizontal forces caused by ground shaking. With available materials, students will use diagonal bracing, shear walls, and rigid connections.
Materials:
1 Piece of Styrofoam to act as base (per group)
MarblesCoffee can lids
Piece of wood or platform
Cardboard Box Lid
Lots of Styrofoam sticks (2.5 X 2.5 X 15 cm) at least 20 per structure
String
Paper clamps
Lots of toothpicks (around 20 per structure)
1 square of tag board (7” square) for shear wall per structure
2 right triangles of tag board (per group) for rigid connections
1 piece of Styrofoam per group to act as a base
Different weights of books
Paper for final design of building
1. Teacher or student prepare shake table: Staple plastic lid or lids
(depending on size of board) to board or platform.
* Place marbles under the lid. Experiment with different
amounts and sizes.
* Place marbles, plastic lid, and block of wood in cardboard
box lid to contain movement.
* Provide a brief review covering different building structures and
structural elements useful for directing forces.
2. Practice group manners and team skills by first building a three-story
structure out of playing cards.
* Instruct students that they are not allowed to bend, brace,
or lean their cards on a support.
3. Divide students into groups of four.
* Explain to groups that they need to agree on a basic design
and construction.
* They will be given a certain time.
* Teams will be responsible to keep within budget, or explain
optional plan.
* Teams will need a sketch of their design.
* After presentation and shake table trial, team members will
be required to write about the process, including design decisions,
successes, and failures.
4. Buildings will be tested for strength (weights placed on top)
resistance to shaking (shake table).
* Explain to students that they have a (optional) $20 budget
for their building project.
* Reinforcements will improve the strength of their building,
but will add to the building costs.
* Each Styrofoam building block will cost $0.25, toothpicks
$0.05, foam base $5.00, 12 inches of string $0.25, etc.
5. Instruct a team member to ‘buy’ supplies and record amount
purchased and total spent.
* Additional supplies need to be purchased from teacher.
6. After completion of building, have teams test in front of class.
* Teams are required to present their designs, and explain
their structures.
* Ask team members to predict their buildings strengths and
weaknesses.
* Test on shaking table and apply weights (different weights
of books, team chooses).
* Time how long the structure is able to withstand shaking
and hold the greatest stress before breaking.
* Students are not allowed to touch their structures during
testing.
* Video “earthquake” drama
7. Upon completion of testing, ask teams to describe how their structures
behaved during the tests.
* Instruct students to record and evaluate their building
project in their journals.
* Show winning teams video and class evaluate strengths and
weaknesses.
Name: __________________________________________ Period: ______________________________________
Record wavelength times in the data table below in the
appropriate place for each assembly.
Repeat the measurement four (4) times.
* Start the stopwatch as the block reaches its
maximum swing and start counting with zero, otherwise you will end up
timing nine swings. Practice!!
* Calculate the average time for each wavelength by adding four
measurements and dividing by four (4).
* Calculate the natural frequency. Divide 10 cycles by the average time.
Frequency is measured in hertz, or cycles per second.
| Rod
Assembly
Wavelength Time (sec/10 cycles |
Avg. Wavelength Times (sec/10cycles) |
|
Trial 1
Trial 2
Trial 3
Trial 4 |
Natural Frequency (cycles/sec) |
| Rod # 1 |
| Rod # 2 |
| Rod # 3 |
|
1. How much variation do you observe among the three tables?
2. What relationship do you notice between the height of the rods and their natural frequency?
3. Measure the height (cm) of each rod assembly from the
base to the top of the block.
4.Plot the height versus the natural frequency of each rod
assembly on the graph.
5.What kind of line was made from the data?
6.As the height of the rod gets larger, what happens to the natural frequency?
|
NATIONAL SCIENCE EDUCATION STANDARDS, National Academy Press, Washington, DC, 1996.
NSTA PATHWAYS To the Science Standards, NSTA, 1996.
Twin Falls School District 411 Science Curriculum Standards, 1998.
Rapid Visual Screening of Buildings for Potential Seismic Hazards: A Handbook, Earthquake Hazards Reduction Series 41, FEMA, 1988
Earthquake Risk in Idaho, Othberg, K. and Breckenridge. R, IGS, Idaho Bureau of Disaster Services.
Seismic Zones and Building Codes: An exercise in rapid visual screening of buildings in Sandpoint, Idaho, Weiser, S. and Breckenridge, R, IGS, 1999.
Seismic Sleuths, EARTHQUAKES 7-12, American Geophysical Union, FEMA – 253, 2nd Edition, October 1995.
Earthquakes, Bolt, Bruce A., W. H. Freeman and Company, 1993.
Loma Prieta Earthquake of October 1989, Earthquake Engineering Research Institute, video.
The EERI Northridge Earthquake CD-ROM, EERI with supports from FEMA and NSF. Contains Volumes 1 and 2 of the Northridge Earthquake Reconnaissance Report (800 pages) and The Northridge Earthquake Slide Set (70 slides), and Highlights of the Northridge Earthquake Videotape.
|
