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Bridge Building Activities for the Reach for the Sky

After-School Program

October 2008

Designed by

S. Selcen Guzey, Tamara Moore, and Gillian Roehrig

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Table of Contents

Objectives……………………………………...…………………………………………... 3

Standards Addressed by Activity………………………………………………………….. 3

Part I: Exploring Civil Engineering………………………………………………………..

4

Part II: Bridge Construction………………………………………………………………. Building your own paper bridge………………………………………………….. Building columns………………………………………………………………….

6 6 17

Part III: Types of Bridges………………………………………………………………….

22

Part IV: Designing the Least Expensive Bridge…………………………………………...

29

Part V: Bridge Model Eliciting Activity (MEA)…………………………………………. 33

Appendix…………………………………………………………………………………... 47 Pre-Post Test……………………………………………………………………….. Pre-Post Test Answer Key…………………………………………………………. Glossary……………………………………………………………………………. Resources…………………………………………………………………………...

48 52 56 57

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Bridge Building Activities for the Reach for the Sky After-School Program

Objectives:

Students will:

• Understand the benefits of a career in civil engineering and how civil engineers affect our lives.

• Expand their vocabulary of bridges, bridge structures and construction, and mathematic concepts such as geometry, algebra, and reasoning.

• Learn about material terminology such as stress, failure, compression, and tension.

• Define similarities and differences between different types of bridges (e.g. beam, truss, arch, suspension, and cable-stayed).

• Evaluate the strength and stability of each type of bridge.

• Design and build bridges.

• Present their bridges and test how strong they are.

• Create a procedure to decide on what type of bridge they should build in a particular area.

Assessment:

Students will be assessed using the following methods:

• Blogs posts

• Student activity worksheets

• Pre-post test

• Bridge designs (K’NEX and West Point Bridge 2007 Software)

• MEA procedure

Standards Addressed:

National Science Education Standards (NRC): Students will develop

Content Standard B: an understanding of motions and forces. Content Standard E: abilities of technological design and understanding about science

and technology. Content Standard F: an understanding of science and technology in society. Inquiry Standard: abilities to do scientific inquiry and an understanding about scientific inquiry.

National Educational Technology Standards: Students will Standard 6: employ technology in the development of strategies for solving problems in

the real world and use technology resources for solving problems and making informed decisions.

Standards for School Mathematics (NCTM): Students will

Geometry: use visualization, spatial reasoning, and geometric modeling to solve problems.

Data Analysis and probability: formulate questions that can be addressed with data and collect, organize, and display relevant data to answer them.

Problem solving: apply and adapt a variety of appropriate strategies to solve problems.

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Part I: Exploring Civil Engineering

Time requirement: 1 class period Materials needed: Computers with internet access (you may need a computer lab for this lesson) Rationale/Goal: Students will

• gain understanding of the engineering field.

• explore civil engineering. Suggested Procedure:

1) Introduce students to bridge building activities. 2) Distribute the pre assessment test, have students complete and return when finished 3) Ask students questions about their career choices. 4) Lead a discussion on career choices in engineering. You may ask any of the following

questions: a. What is engineering? b. What do engineers do? c. Do you think there are other types of engineers?

i. Goals: try to get students to come up with different types of engineers and understand that what makes engineering different than other fields is that they go through a design cycle

ii. A sample of engineering design process that engineers use to design something to solve a problem is: Ask, imagine, plan, create, and improve.

5) Introduce the field of civil engineering and tell students they will be viewing two short clips about civil engineering. http://www.youtube.com/watch?v=Wgrt4SXU2Ks (Introduction to civil engineering, 2:18) http://www.livevideo.com/video/B55D495429074D53AD06A10DDB524041/civil-engineering-jobs-jobs-.aspx (civil engineers job description, 1:19)

or go to http://reachforthesky0809.ning.org (videos are on the left side of the main page) 6) Hold a discussion of the videos. Ask questions such as what are the things that you

learned about civil engineering? What are some challenges of a career in civil engineering? What kind of project do you think civil engineers work on? What would you study to become a civil engineer? What are some examples of civil engineering projects found in our community?

7) Remind students their new 35W Bridge site trip in summer 2008. Ask questions such as where is the new bridge located? What kind of structure is it? What is the new bridge made of? What parts of it really makes the bridge stand up? What kind of challenges did civil engineers face when designing and building the bridge?

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Answer Key The new 35W bridge is located in Minneapolis. It is a 1,216-foot-long, 10-lane concrete bridge. The bridge has 3 piers (4 columns in each pier) and the main span is 504’ long. The engineers considered the safety issue while designing the bridge. They used concrete to provide superior durability. Pictures of the new 35W bridge:

Pictures are taken from: http://projects.dot.state.mn.us/35wbridge/index.html

Closing:

1) Lead the students in a discussion of what they have learned. 2) Tell students that they will continue to explore about the structure of the new and old

35W bridge in the following day.

Assessment: The students will write a short paragraph describing a career in civil engineering. Students will explain what a career in civil engineering would require, the description of the job and why this would be an interesting career choice. Ask students to upload their essays on their Blogs on Ning (http://reachforthesky0809.ning.com/). Lesson Extension:

Teachers may ask students to do an internet search on famous civil structures and make a short presentation on the following day.

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Part 2: Bridge Construction

-Activities are adapted from “Design it: Engineering in after school program” Curriculum-

Activity 1: Building your own paper bridge

Time requirement: 1 class period Rationale/Goal:

Students will

• experience bridge structure.

• learn about balance, forces (e.g. tension and compression) and beams. Materials:

Computers with internet access (you may need a computer lab for this lesson) Video on 35W bridge collapse (http://reachforthesky0809.ning.com) Student worksheet (p. 16) Copy paper Small drinking cup Clear tape Steel washer or nails Cardboard square (4 inches x 4 inches) Books or boxes Suggested Procedure:

Before the class: 1) Before the class, please read the newspaper article about 35W bridge collapse (p.10). In the class: 1) Ask questions about 35W bridge collapse. Lead a discussion on factors that might have

caused the bridge collapsed. 2) Show the video about 35W bridge collapse. 3) Lead a discussion on bridge construction and design. Ask any of the following questions:

• How can we design a structurally stable bridge?

• What factors do civil engineers take into consideration when designing a bridge? (i.e. work load)

4) Explain students parts of a bridge- beam and columns Beam is a compact horizontal piece of material that supports weight across a gap.

Column is a vertical support that designed to take vertical loadings. 5) Go to http://www.pbs.org/wgbh/buildingbig/lab/forces.html for the virtual lab on the

forces that act on the different parts of the bridge structure. Note: If you do not have internet access explain forces using copy papers.

Compression: A force that acts to squeeze the paper. Tension: A force that acts to stretch the paper. Torsion: A force that acts to twist the paper. Shear (sliding): A force that acts opposite directions against the paper. Flexure (bending): A force that acts to bend the paper.

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Figure 1: Compression (squeezing) Figure 2: Tension (stretching)

Figure 3: Torsion (twisting) Figure 4: Shear (sliding) Figure 5: Flexure (bending)

6) Ask each student to complete the worksheet (p.16). 7) When students finish their worksheets group students (groups of 2-3) for the “challenge.” 8) The challenge: students will make a bridge that spans an 8 ½ inch wide “river” using only

four sheets of paper. They will attempt to make the strongest bridge. Rules: The bridge must sit on the riverbanks without any extra help and no part of the bridge may touch the “water”.

9) While students work on their design ask any of the following questions:

• Why did you decide to place that piece of paper/tape in that position?

• Does it matter how tight/loose you roll the beams?

• What shapes can you make your paper into? Which are the strongest?

• Where is the strongest/weakest part of your bridge? 10) Table 1 (p. 9) includes a list of strategies that students may use in this activity. 11) When students finish building their bridges give each team a small square of cardboard, a

cup, and some washers (or small heavy metal pieces) to test their bridges. The following figure shows how to add load.

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Figure 6. Adding load

12) Have student teams participate in a small competition to find whose bridge structure is more structurally stable. To do this, have teams put increasing weight (in equal increments) in their cup and record the amount of weight the bridges held. If possible record the competition with a video camera and upload it into Ning (http://reachforthesky0809.ning.com/).

13) After students test their bridges ask them following questions:

• What part of your bridge is the strongest?

• How can you change your bridge design to make it stronger? 14) During the discussion, try to draw out the following points:

Beam is a compact horizontal piece of material that supports weight across a gap. Compression: A force that acts to squeeze a material. Tension: A force that acts to stretch a material Torsion: A force that acts to twist a material. Shear (sliding): A force that acts opposite directions against the paper. Flexure (bending): A force that acts to bend a material. - The paper is stronger in the form of a beam rather than a flat sheet or board. - A good shape of a beam is cylinder - The tighter the cylinder is rolled, the stronger it seems to become.

15) If time allows, have students make a second bridge that spans the length of the paper (11 inches). Use 6 sheets of paper this time.

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Table 1: Building Strategies

Source: Design it! Engineering in after school program

Lesson Extension: You may find helpful for students to investigate more about bridge disasters. The following web sites provide information, pictures, and videos of famous bridge disasters. Ask students to visit any of these following web sites.

http://iti.acns.nwu.edu/links/bridges/disasters.html

http://eduspace.free.fr/bridging_uerope/disasters.html

http://www.engr.utexas.edu/wep/COOL/AcifRiver/allaboutbridges_Disasters.html

http://www.lib.washingtom.edu/specialcoll/tnb/

http://www.ketchum.org/brdigecollapse.html

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Newspaper Article on 35W Bridge Collapse

Source: http://www.startribune.com/local/11593606.html

4 dead, 79 injured, 20 missing after

dozens of vehicles plummet into river

By Paul Levy, Star Tribune

August 2, 2007

Emergency crews have resumed their

recovery and clean up efforts at the scene of

the Interstate 35W bridge that collapsed

during rush hour Wednesday evening.

Authorities lowered the number of

confirmed fatalities to four, but said they

expect the number to change throughout the

day.

Doctors at Hennepin County Medical Center

said at a news conference this morning that

79 people were injured in the disaster.

One of them died around midnight of blunt

force trauma, consistent with chest injuries

from falling 64 feet.

Fifty-five people were transported to area

hospitals including 24 to HCMC. Six of

those had life-threatening injuries, 10 were

listed in satisfactory condition and eight

were treated and released.

Twenty-four people made it to hospitals on

their own.

Dr. John Hick, who was one of the first

responders to the bridge collapse, said "It's

somewhat of a miracle that (the number of

injuries and fatalities) was that low."

Hick also praised work done by passersby

and people in area who jumped in to assist

police and paramedics with evacuating

injured.

Dr. William Heegaard, who operated on

some of the injured, said the hospital cleared

out 25 rooms in ICU to deal with the

expected flood of injuries.

He said at one point the hospital had 10

operating rooms available and that a number

of surgeries were performed. "They were in

shock, they were happy to be alive, but they

felt sad for all the people they had seen," he

said.

Doctors said the types of injuries dealt with

included head, arm, leg internal injuries

"They may make it, but some of the may

not, said Dr. Douglas Brunette.

Police Chief Tim Dolan said at a news

conference this morning that 20 to 30 people

were still missing.

Dolan said many vehicles were still in the

water.

"The recovery involving those vehicles and

the people who may be in those vehicles is

going to take a long time," Dolan said.

"We're dealing with the Mississippi River.

We're dealing with currents, and we're going

to have to do it slowly and safely."

Police Lt. Amelia Huffman said the number

of confirmed fatalities had been lowered

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from seven to four. "This morning, the

medical examiner's office only has four sets

of remains," she said.

Mayor R.T. Rybak said the police

department's number is based on the medical

examiner's information, but he still

considers there to be seven fatalities — and

he expects more.

"I think you can expect that to be a dynamic

situation for a while," he said.

Crews in boats were using sonar to search

the water, said Hennepin County Sheriff

Rick Stanek. The bridge is too unstable to

allow divers into the water, he said.

As the sun rose this morning at least two

patrol boats were visible on the river south

and east of the lock and dam and just

uptream from the collapsed bridge.

Many rescuers who'd been at scene as late as

2 a.m. were expected back at 6 a.m. for an

operations briefing. Then, they were going

to go back onto the water.

An hour before sunrise, nearly a dozen giant

lights mounted on the Cedar Avenue and

surviving parts of I-35W bridge illuminated

river surface.

The 1,907-foot bridge fell into the

Mississippi River and onto roadways below.

The span was packed with rush hour traffic,

and dozens of vehicles fell with the bridge

leaving scores of dazed commuters

scrambling for their lives.

Stanek told the Associated Press at about 1

a.m. today that all search efforts had been

called off for the night and that searchers did

not expect to find any survivors.

Wednesday night, Gov. Tim Pawlenty said

the bridge collapse "is a catastrophe of

historic proportions for Minnesota."

Between 50 and 60 vehicles were on the

bridge when it went down shortly after 6

p.m., authorities said. Legions of rescue

workers and volunteers swarmed to the

scene and spent hours sifting through the

wreckage in a frantic search for survivors.

By late in the evening, officials said efforts

at the Mississippi had switched from rescue

to recovery.

Jay Danz, 45, of St. Paul, was on his way to

the Metrodome to watch the Twins play

Kansas City and had driven under W. River

Parkway, beneath the interstate bridge,

seconds before it fell.

"I heard it creaking and making all sorts of

noises it shouldn't make," Danz said. "And

then the bridge just started to fall apart."

In addition to the cars that went into the

water, a school bus carrying about 60

Minneapolis children fell from the bridge,

landing on all four of its tires and missing

the water as it came to rest near the

parkway.

Several of the children and at least two

adults were treated for injuries after the

group escaped through the back door of the

bus.

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"Some kids had blood on their faces, but

thank God everybody could move," Danz

said.

Bernie Toivonen of Minneapolis was

southbound on I-35 Wednesday when he

saw the bridge in front of him buckle.

"I knew it was going down," he said.

Toivonen scrambled out of his vehicle, and

helped others who were stranded among the

wreckage.

"I helped a lady get out of a minivan. She

was at a real steep angle. There were people

screaming."

Toivonen said that below him 40-50 feet

was a tabletop of concrete. He scrambled

down to the scene and found a man who he

said, "had a chunk of a beam on his arm and

a piece of concrete on his head."

The cause of the collapse wasn't known in

the hours afterward. It's too soon to know

what happened, said Catherine E. Wolfgram

French, a civil engineering professor at the

University of Minnesota.

"Things can happen with temperature, and

with construction, or a lot of other

confounding factors," French said.

This was a 40-year-old truss bridge, and

French did say that some early truss bridges

don't have as many structural redundancies -

- backups to carry the loads -- as is now

considered desirable.

Another engineer, Michael Ramerth, a

principal at MBJ Consulting Structural

Engineers in Minneapolis, said in the search

for answers "I would start at the

foundations."

On a typical weekday, more than 100,000

cars use the bridge.

Berndt Toivonen, 51, of Minneapolis, was

on his way home from a painting job when

the bridge collapsed beneath his car.

"The bridge started to buckle," Toivonen

said. "It went up and came down. I thought I

was going to die."

Bumper-to-bumper traffic

What people in the area of the collapse

experienced or saw at about 6:05 p.m.

unfolded as motorists crawled bumper to

bumper across I-35W toward the end of rush

hour.

Those on the bridge felt buckling and

swaying and heard a crunching.

Then came the unthinkable: The 40-year-old

bridge collapsed, dumping vehicles into the

water and onto land below. That was

followed by scenes of frantic, bloodied

motorists and rescuers who converged on

the scene.

Many vehicles, including at least one

semitrailer, were on fire. People were

reported to be floundering in the river.

Rescuers rushed to help people escape cars

trapped in the V-shaped hollow where the

bridge had caved in.

The school bus that fell was, returning from

a day-camp swimming trip sponsored by a

Waite House summer program.

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"We collapsed," said Ryan Watkins, one of

the children.

Crumpled wreckage lay on the east bank of

the river, and a huge section of concrete

roadway lay on the west bank. Down below

in the river gorge, rescue workers scrambled

to help people get out of the water.

Fire and black smoke rose from the

wreckage.

Memorial Blood Centers and the American

Red Cross put out immediate calls for blood

donors. A center for families of those who

are missing was set up at the Holiday Inn

Metrodome.

Homeland Security Secretary Michael

Chertoff issued a statement Wednesday

night saying there was no indication of

terrorism.

Transportation Secretary Mary Peters was

scheduled to fly to the Twin Cities early this

morning, along with Sens. Norm Coleman

and Amy Klobuchar.

Workers on the bridge

About 20 construction workers employed by

Progressive Contractors Inc. were about to

begin night shift work on the bridge when it

collapsed, company officials said.

The company has been working on a repair

project for about six weeks, said Mike

McGray, president of the company.

Progressive is based in St. Michael, Minn.,

and is one of the state's major road and

bridge repair contractors.

In 1990 a construction worker fell 90 feet to

his death when a concrete arch span on the

Lake Street-Marshall Avenue Bridge

collapsed into the Mississippi River. In 1960

a bridge over the Minnesota River at Hwy.

41 in Chaska collapsed during construction.

No one was killed in that incident.

Construction workers had been repairing the

bridge's surface as part of improvements

along that stretch of the interstate. There

were a large number of construction workers

who went into the water, said Maj. Michael

Asleson of the Minnesota State Patrol.

Most of the injured were taken to Hennepin

County Medical Center.

Nine people were taken to North Memorial

Medical Center in Robbinsdale and five

others arrived by ambulance at the

University of Minnesota Medical Center.

A staging area for the injured was set up

near the Stone Arch Bridge.

Marcelo Cruz, 26, of Crystal, who has used

a wheelchair since being paralyzed in a

shooting in South Carolina several years

ago, was driving his van across the bridge

toward downtown when he felt it began to

wave up and down.

He steered into the concrete railing to stop

himself from driving into the river, and saw

many cars on the bridge fall into the water.

His van came to rest steeply inclined toward

the river and several onlookers ran and told

him to get out. He said he needed help and

the onlookers carried him out of his van in

his wheelchair to safety on the riverbank.

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"I'm lucky to be alive," he said over and

over again.

Peter Siddons, a senior vice president at

Wells Fargo Home Mortgage, was heading

north over the bridge toward his home to

White Bear Lake when he heard

"crunching."I saw this rolling of the bridge,"

he said. "It kept collapsing, down, down,

down until it got to me."

Siddons' car dropped with the bridge, and its

nose rolled into the car in front of him and

stopped.

He got out of his car, jumped over the

crevice between the highway lanes and

crawled up the steeply tilted section of

bridge to land, where he jumped to the

ground.

"I thought I was dead," he said. "Honestly, I

honestly did. I thought it was over."

Ramon Houge of St. Paul was on his way

home from work and was on the bridge

when he heard a rumbling noise and cars in

front of him began to go down.

He said cars that could backed up, turned

around and drove toward safety.

Baseball game added to congestion

Danz said there were cars behind him on W.

River Parkway, but he didn't think any of

them were under the bridge when it fell.

John Joachim of Taylors Falls, Minn., took

I-35W to the Twins game and said traffic

suddenly "slammed to a stop" as he neared

University Avenue.

"I didn't know what was going on but a huge

cloud of dust rose in front of us," he said.

After the game, traffic were being rerouted

away from the collapse, routes that also

were being used by theater patrons leaving

the Guthrie.

This afternoon's Twins game has been

postponed, along with scheduled

groundbreaking ceremonies for the new

baseball park that had been scheduled for

this evening.

'Five feet from the edge'

Louis Rogers, 28, of Roseville was driving

home from work listening to music in his

Chevy Blazer when the bridge gave way just

feet in front of him.

"It just disappeared; it made no sound

whatsoever," he said. "It was pretty much

like a thud, not too loud of a thud. The next

thing I know, cars were dropping and there

was smoke. My car was no more than five

feet from the edge."

Rogers tried to help some of the people in

cars that had fallen into the river and

stopped on the bridge.

"I saw a lady in a car and I screamed, but I

got no response," he said. "I grabbed my bag

and started signaling cars to get out of

there."

Ryan Murphey, 30, of Minneapolis, went to

the scene to see if he could help out.

"It looked like a terrorist attack, a complete

catastrophe," Murphey said. "But everyone

there was very calm and organized."

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He helped remove two victims from the east

side of the bridge on stretchers, including a

woman in her late 50s with a "bloody face."

The Twins decided to play Wednesday

night's game, but only after the public

address announcer alerted the crowd at 7:08

p.m. of the bridge's collapse. A moment of

prayer followed. It was then announced that

the game would go on so emergency crews

could perform their duties without the added

pressure of having 20,000 to 25,000 people

scrambling in swarms from the Dome area.

Area law enforcement, including the

Hennepin County Sheriff's Office, had

launched at least three boats to help with the

rescues.

"Unbelievable," said Audrey Glassman of

Minneapolis, who left her work shift at

nearby Spoonriver restaurant to survey the

scene. "You'll never cross a bridge again

without thinking about this."

Red Cross volunteer Eric Pone guessed 100

people came through the Holiday Inn

Metrodome Wednesday searching for word

on loved ones. "For some folks they're

dealing with a sense of relief because they're

loved ones are OK. Others haven't heard

anything."

Ian Anderson rode his bike to the Holiday

Inn to look for his girlfriend, Allysa

Rocklitz, 24, of Burnsville, a waitress at the

Fine Line club in downtown Minneapolis. "I

can't remember a single instance when I

called her and wasn't able to instantly talk to

her," he said. "She calls me all the time and

all of a sudden she's not there.

"Hopefully, I'll get a call tonight. I'll be up

all night, I'm sure of that."

--The Associated Press contributed.

Staff writers Curt Brown, Tim Campbell,

Joe Christensen, Terry Collins, H.J.

Cummins, Pat Doyle, Kevin Duchschere,

Tom Ford, Kevin Giles, Pat Lopez, Maura

Lerner, Bill McAuliffe, Pamela Miller,

Claude Peck, Joy Powell, James Shiffer, Jim

Foti and Doug Tice contributed to this story,

which was written by Paul Levy.

© 2008 Star Tribune. All rights reserved.

Source: http://www.startribune.com/local/11593606.html

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Student Worksheet-Forces

Student’s Name: ………………………… Date: Please write down the forces that are shown in the following drawings. Note: Arrows indicate the forces that act on the materials. 1)

This force is called ……………………………… 2)

This force is called……………………………..

3) This force is called……………………………..

4) This force is called…………………………….

5)

This force is called…………………………………………

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Activity 2: Building Columns

Time requirement: 1 class period Rationale/Goal: students will

• learn about columns

• learn about buckling Materials: One empty toilet paper-towel tube and one empty paper-towel tube for the demonstration Student worksheet (p. 21) Copy paper Clear tape Rubber bands Washers 2 cardboard squares (4inches by 4 inches) Suggested Procedure:

1) Show an empty toilet paper-towel tube and an empty paper-towel tube to students and ask them what happens if any of them put weight on them or stand on them.

2) When students make their predictions have one of the student stand on them 3) Ask them how they can make them stronger (e.g. filling the tube with sand, covering tube

with tape).

Buckling occurs when compressive stresses are too great for the material. Columns are the vertical supports of a bridge and they may buckle if they cannot support the load. How a column behaves depends on the strength of the material it is made from. Generally, a short, wide column can support a greater load than a long, thin one.

Figure 1: Buckling

4) Show students some pictures of long bridges that have columns. You can show the following pictures.

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George P. Coleman Bridge, Yorktown, Virginia

Brooklyn Bridge, New York

19

Sunshine Skyway Bridge, Tampa, Florida

George Washington, New York

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5) Have a discussion on bridges and their columns. Ask any of the following questions:

• What is the best way to place a column under the bridge?

• What is the best shape for bridge columns?

• Where are the strongest and weakest parts of the bridges in the pictures?

• Are tall columns stronger than short columns? 6) Group students for the challenge (2 students in each group). The challenge: Students

make a structure at least 4 inches high with only 4 sheets of paper. They then test and record how much load it can carry.

7) Ask students make their columns. (Students can make columns round, square, or triangular. They can make them narrow or wide)

8) Give students their data sheets (on next page). 9) To test how much load a column can carry, students should place one cardboard on the

top of the table and place their columns on it. Put the second cardboard on top of the columns and place the smallest load on the top square. Record the load and continue to add more load. Textbooks can be used for load. Allow students to take pictures while testing their designs. Note: Students will post these pictures on Ning later.

10) Ask students write down the loads on their worksheet (p.21) 11) Lead a discussion using any of the following questions:

• What makes some columns stronger than others?

• What is the best shape for the columns? (round, square, etc.)

• Which one is better? Long columns or short columns?

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Student Data Sheet:

Team members: Date: ……………………………………………….

Each time you test your structure, one team member should write down the predictions and the largest actual load it carried without breaking and collapsing.

Trial# #Columns Height Diameter Shape Predicted load (ounces)

Actual load (ounces)

1

2

3

4

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Part III: Types of Bridges

Time requirement: 2 to 3 class periods Rationale/Goal: Students will learn the five main types of bridges (beam, truss, arch, suspension, and cable-stayed bridges) Materials:

Pictures of well-known bridges (See page 26, 27, and 28)

K’NEX (each group of students need one set of K’NEX) Weights measured in designated amounts (actual weights: 10-1000 grams, books etc.) Suggested Procedure: Before the class: 1) Please read the below information regarding the five main types of bridges.

i: Beam bridges are the simplest kind of bridges. They have one horizontal beam with two columns. It is typically used to span short distances. However, several beams can be linked together to build beam bridges to span long distances as in the case of Chesapeake Bay Bridge-Tunnel (The length of this bridge is 79,200 feet). Wood, concrete, steel, and stone can be used to build beam bridges.

Forces that act on beam bridges: Load Note: The arrows that point together represent compression and the arrows that point apart represent tension.

ii: Truss bridges are a type of beam bridge in which the beam is constructed from triangle sections. This type of bridge is usually made from steel. The longest steel truss bridges are around 500 m long.

Forces that act on truss bridge:

Compression

Load

Compression

Compression

Tension

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iii: Arch bridges are very strong bridges. Wide range of materials (i.e. stone, metal) can be used to build arch bridges. Arch bridges can be built for both short and long distances.

Forces that act on arch bridge:

iv: Suspension bridges span long distances. However, it is very expensive and very challenging to build suspension bridges. The need for large amount of material and labor intention increase the cost.

Forces that act on suspension bridge:

v: Cable-stayed bridges span medium distances. These bridges are visually appealing. However, cable-stayed bridges are very expensive to build as in the case of suspension bridges. Labor intention increases the cost.

Compression

Tension

Load

Compression

Load

Compression

Compression

Tension

Compression

Load

Tension Tension

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Forces that act on cable-stayed bridge: In the class:

1) Have a discussion about different types of bridges that students have seen. 2) Show pictures of well-know bridges (see page 26, 27, and 28). And then ask students any

of the following questions.

• Are they long or short?

• What factors might engineers consider while designing these bridges? (i.e. river, traffic)

• What do you think they were designed to transport? (i.e. pedestrian, vehicles, train)

Answer Key:

The beam bridge: The Eagle County Road Bridge is a short bridge. Engineers focused on the length of the span while designing this bridge, because the forces acting on a beam bridge tend to compress the top of the bridge. If the bridge is long and heavy piers become under compression. This bridge was built as functional walkway. The truss bridge: The Smithfield Street Bridge span medium distance (less than 300 feet).The engineers considered the river traffic while designing the bridge. There are a couple piers on the river and the bridge has a short clearance. The bridge was designed to transport vehicles. The arch bridges: The Rogue River Bridge spans a long distance. The engineers considered the weight of vehicles since the bridge itself apply large forces at the base of the arch. This bridge was designed to transport vehicles. The suspension bridge: The Golden Gate Bridge spans a very long distance. The engineers considered earthquake and wind while designing this particular bridge. This bridge was designed to transport pedestrian and vehicles. The cable-stayed bridge: The Sunshine Skyway Bridge spans a long distance. The engineers considered the weight of the material that structure is made of. The bridge was built to transport vehicles.

Compression

Load

Tension Tension

25

3) Discuss about the similarities and differences among different types of bridges. 4) Group students (2 to 3 students in each group). Provide each group the K’NEX education

kit (Note: The booklet in the kit shows how to connect different pieces). 5) Each group of students should build all 5 types of bridges in an order starting with beam

bridge (Beam bridge, truss bridge, arch bridge, suspension bridge, and cable-stayed bridge). Give 20-30 minutes for each group of student to build each type of bridge. After they build a bridge ask them to test how strong the bridge is. Provide them the weights (10-1000 grams or books). Allow students take pictures or videos when they testing their bridges. Note: Students will upload these pictures and videos on their personal Blog.

6) Lead a discussion on the strengths and weakness of each type of bridge. Possible answers can be found in the following table.

Bridge Type

Advantages

Disadvantages

Beam bridge -Easy to build -Inexpensive

-Short span range -Not aesthetic

Truss bridge -Strong and rigid framework -Work well with most applications

-Cannot be use in curves -Expensive materials needed

Arch bridge -Aesthetic -Used for longer bridges with curves -Long life time

-Abutments are under compression -Long span arches are most difficult to construct

Suspension

bridge

-Light and flexible -Aesthetic

-Wind is always a concern -Expensive to build

Cable-stayed

bridge

-Cables are economical -Fast to build -Aesthetic

-Stability of cables need to be considered for long span bridges

7) Ask students to upload pictures and videos that they took while testing their bridges to

their Blogs. Also, ask them to answer the following questions on their Blogs.

• How strong were the bridges that you built?

• How did you test your bridges?

26

Pictures of Famous Bridges

Beam Bridge:

Eagle County Road Bridge, Colorado

Truss Bridge:

Smithfield Street Bridge, Pittsburg, PA

27

Arch Bridge:

Rogue River Bridge, Gold Beach, Oregon

Suspension Bridge:

Golden Gate Bridge, San Francisco, California

28

Cable-Stayed Bridge:

Sunshine Skyway Bridge, Tampa, Florida

29

Part IV- Designing the Least Expensive Bridge

Time requirement: 3 class periods

Rationale/Goal: Students will use the West Point Bridge Design 2007 software to design the least expensive truss bridge. Materials: Computers with West Point Bridge Design 2007 Software Information about Truss Bridges for teachers (see below)

Truss Bridges

There are more than a half million bridges in the United States. This number includes all

the bridges greater than 20 foot and carry roadways on it. Thousand of us cross bridges everyday. While crossing a bridge, how many of us think about how engineers design a bridge or how engineers decide which bridge to build. When we think of a bridge, many of us remember only the Truss bridges because these bridges are very common in the United States.

Truss bridges’ frames consist of a series of triangle shapes. The triangles transfer the load

from the deck to the piers (bold words are defined in the glossary at the end). The truss bridge deals with two types of forces called tension and compression. While compression acts to compress or shorten the parts of structure of the bridge, tension acts to expend or lengthen the structure. The design of the bridge should handle these two forces. To deal with these forces, engineers use various materials and strengthen the structure of the bridge. For example, truss bridges are commonly made from cast iron, steel, or combination of these materials.

There are two main types of truss bridges: through trusses and deck trusses (see figure 1 on p.31). In a truss bridge, the deck can be located over or within the bridge structure. In a through truss bridge, the deck is located through, or in the middle of, the bridge structure. In a deck truss bridge, the bridge structure is under the deck.

In addition, a truss bridge can involve various types of frame structures. The most

representative truss bridges are Pratt truss, Howe truss, and Warren truss (see figure 1). A Pratt truss has vertical compression members and diagonal tension members. Except the very end members, all the diagonal members slant down toward the center of the span. The diagonals are in tension and the verticals in compression. This structure allows using thin diagonal members located near the center. The Pratt truss can be used with spans up to 250 feet. In a Howe truss, the vertical members are in tension and the diagonal members are in compression, the opposite structure of a Pratt truss. The diagonal members of the Howe truss slant toward the bridge end. The need to use thick steel to support the diagonal members makes it uneconomical design. Warren bridges are the simplest truss bridges. They usually do not have any vertical members, but to strengthen the bridge, vertical members can be used.

30

Glossary:

Abutments: supports of the each end of the bridge Deck: the structure that caries the road, path, or the railway. Members: connected elements (verticals and diagonals) that form truss bridge Pier: an upright support of the span of a bridge Span: a part of a bridge that extends between two supports

31

Student instructions: Select one type of bridge and build it according to the illustrations below using West Point Bridge Designer 2007. After building the bridge, identify the characteristics of the bridge. Share your findings with others who build different type of truss bridge.

Through Truss Warren Through Truss

Pratt Through Truss

Howe Through Truss

Deck Truss

Warren Deck Truss

Pratt Deck Truss

Howe Deck Truss

Figure 1. Images demonstrating through and deck trusses, as well as Warren, Pratt, and Howe trusses. All images were generated with West Point Bridge Designer 2005.

32

Suggested Procedure: Before the class:

• Please complete tutorial from http://bridgecontest.usma.edu/tutorial.htm to get experience with the West Point Bridge Software. In this tutorial you'll use the West Point Bridge Designer 2005 to design a steel truss bridge.

• Please install the West Point Bridge Designer 2007 software to the student computers. The software work only on PCs. There is no Macintosh version of this software.

• Students do not need to register for the bridge contest! In the class:

1) Give students information about truss bridges. You can use the above article for information.

2) Discuss about the structure of truss bridges. Ask any of the following questions:

• What are the advantages and disadvantages of truss bridges?

• What kind of materials can be used to build truss bridges?

• What are the basic types of truss bridges?

3) Group students for the challenge (max 2 students in each group). The challenge: Students will try to design the least expensive truss bridge using West Point Bridge 2007 software.

4) Give information about the West Point Bridge software. You can use the following information which is taken from the web site (http://bridgecontest.usma.edu/)

The software provides students with the tools to model, test, and optimize a steel highway bridge, based on realistic specifications, constraints, and performance criteria. The software allows students to:

• Learn about engineering through a realistic, hands-on problem-solving experience.

• Learn about the engineering design process--the application of math, science, and technology to create devices and systems that meet human needs.

• Learn about truss bridges and how they work.

• Learn how engineers use the computer as a problem-solving tool.

5) Ask students design their bridges using West Point Bridge software 6) Save students’ bridge designs. 7) Ask students to Blog about their bridge design. Students need to find answers to the

following questions and Blog about them.

• How did you design your bridge?

• What did you consider while designing your bridge?

• How did it go?

• How did the structure of your truss bridge look like?

• Which parts of your truss bridge stress from tension and compression?

33

Part V: Bridge MEA

Time requirement: 2 class periods Rationale/Goal: Students will create a model to build a bridge in a particular location. Material: Bridge MEA (see below) Pictures of bridges (see p.39-46) Suggested Procedure:

Students individually read the article to extent their knowledge on 35W bridge collapse. This article is on page 34. Students then watch a short clip on bridge collapse and then individually answer the guiding questions. These questions are also on page 34. Once students finish their responses give students the Internal Memo and ask them to read the Internal Memo individually. The Internal Memo is on page 35. Afterwards, place the students in teams of three to four. After students choose a name for their team, present the problem. The problem is on page 36 (You may want to give at least one hard copy of the problem to each group).

In teams, students work on the problem for 90 minutes. Each team needs to write their

solution in a letter to Mn/Dot. Then, they present their solutions to the class. You may give five minutes to each group to present their solution. At the end of the class presentation, students upload their letters to Mn/Dot into their Blogs. When Blogging is over collect student teams’ memos.

34

Model Eliciting Activity-Part A Bridge Design-Individual Activity

Read the following information and individually answer the questions that follow.

35W Bridge Collapse

Background material adapted from Mn/Dot Bridge website (http://www.dot.state.mn.us/bridge/ )

The Interstate 35W Mississippi River Bridge in Minneapolis collapsed on August 1, 2007. The eight lane bridge was Minnesota’s busiest, carrying 140,000 vehicles a day. This deck steel truss bridge was 1,907 feet long and had 14 spans. It was open to traffic in 1967 and expected to be reconstructed in 2020-2025. The bridge was inspected every two years until 1993; after that it was inspected every year.

Starting in 1997, deficiencies were demonstrated in inspection reports. Mn/Dot attempted to improve the condition of the bridge through bridge span rehabilitations. Furthermore, in 2001 Mn/Dot worked with civil engineers from University of Minnesota to evaluate the fatigue stress within the truss. Following the field tests, the civil engineers recommended that fatigue cracking was not expected to be a problem in the truss but reported that some critical locations of the trusses had high stress and some girders were distorted. The bridge’s last inspection was completed in June 15, 2006. As a result of comprehensive analysis on fatigue and fracture structure recommended supporting the critical 52 truss members.

During the 35W bridge collapse, 13 people were killed and more than 100 injured. The investigations on the collapsed bridge continue. Mn/Dot has investigated every single detail to find what caused the bridge collapse. It has been considered that gusset plates in the center span and the extra weight from construction may have contributed to the tragedy. The gusset plates are steel plates that tie steel beams together on a bridge. These are a very important structural component of truss bridges. However, it should be also considered that gusset plates are not the only structural components in truss bridges; other critical parts of the bridge might have deficiencies. In addition, extra weight may not be a main factor for the bridge collapse since the bridge had less than its usual traffic at the time of the collapse. Half of the lanes were closed for the repair when the bridge failed.

Individually:

• Watch the video of 35 W bridge collapse from http://www.youtube.com/watch?v=osocGiofdvc Or go to http://reachforthesky0809.ning.com

• Generate a list of factors you believe are involved in the 35W bridge collapse.

• Generate a list of factors that you need to consider when designing a bridge.

• Once you have finished your individual response, request the memo from Mn/Dot. Read the memo individually and then let your instructor know that you are ready to proceed.

35

INTERNAL MEMO

To: White Earth Engineering Team From: Mn/Dot Re: Bridge Design

After the I-35 W bridge collapse, Mn/Dot has focused attention on the condition of other

bridges in Minnesota. Mn/Dot conducted recent inspections on bridges in the Minnesota and

found that there are 1,907 bridges that are structurally deficient. As a result of recent inspections,

Mn/Dot shut down another bridge in March 2008. Originally, the bridge was scheduled for

replacement in 2015, but Mn/Dot inspectors found critical deficiencies during the inspection. The

bridge has a similar design configuration as 35W Bridge and it is located over the Mississippi

River in St Cloud. Mn/Dot plans to replace the bridge soon. The new bridge will be located in

the same place as the old one. It will carry a highway and run east-west. The length of the bridge

will be approximately 900 feet. The bridge deck should have two lanes and should also have 5 ft

wide sidewalks along both sides of the bridge.

Starting with the St Cloud Bridge, Mn/Dot will replace many of the bridges that have been

found to be structurally deficient. Because so many bridges are going to be replaced, Mn/Dot

needs a procedure for comparing different type of bridges and choosing the right type of bridge to

build across each span. Mn/Dot is asking you to create this procedure. First, your team should

decide on the least expensive and safest bridge to replace the St. Cloud Bridge. Pay attention to

how you made this decision because we also need you to create a procedure to make the same

type of decision in other locations around Minnesota. Mn/Dot will use your procedure to replace

the St Cloud Bridge and then other bridges. Please find the enclosed information regarding the

types of bridges that Mn/Dot plans to build―truss bridge, arch bridge, suspension bridge, and

cable-stayed bridge. In addition to the information about the major types of bridges, Mn/Dot also

has provided you two examples of four types of bridge in the U.S. You may need to use this

information as a starting point to determine your procedure for selecting the new bridge design.

Please respond in a letter to Mn/Dot explaining which bridge is right for the St. Cloud span and

why you chose it, and provide them with a method to make the decision of which type of bridge

to use to replace any bridge in Minnesota.

Thank you.

Peggy Abrams

Hwy. 23 bridge in St. Cloud, MN.

36

Model Eliciting Activity- Part B Bridge Design- Team Activity

• Read each team member’s individual list of factors that need to be considered when designing a bridge.

• Reread the Memo as a team.

• Write the body of a memo to Peggy Abrams at Mn/Dot that includes: o A clear explanation of what type of bridge you decided to build in St. Cloud and

why you made that decision. o A detailed explanation of your team’s general procedure for choosing the best

bridge type to build across any span and indicate how Mn/Dot can use this procedure to replace other bridges in Minnesota.

37

Table 1: Different Types of Bridges

Bridge Type

Advantages

Disadvantages

Span range

Material

Design

Effort

Truss bridge

-Strong and rigid

framework

-Work well with most

applications

-Cannot be used in curves

-Expensive materials needed

Short to medium

Iron, steel, concrete

Low

Arch bridge

-Aesthetic

-Used for longer bridges

with curves

-Long life time

-Very strong

-Abutments are under compression

-Long span arches are most difficult to

construct

-Relatively expensive

Short to long

Stone, cast iron,

timber, steel

Medium

Suspension

bridge

-Light and flexible

-Aesthetic

-Wind is always a concern

-Expensive to build

Long (up to

7,000 feet)

Steel rope and

concrete

High

Cable-stayed

bridge

-Fast to build

-Aesthetic

-Stability of cables need to be considered

for long span bridges

Medium (500-

2,800 feet)

Steel rope and

concrete

High

38

Table 2: Examples of four major types of bridges

Bridge Name

Location

Bridge Type

Total

length

Clearance

below

Lanes

Constructability Life

time

Cost

(Present

value)

Hennepin Ave

Bridge

Over Mississippi

(Metro area)

Suspension

bridge

1037

feet

37 feet

6

Easy

Fairly

long

(Built in

1990)

$100

million

Golden Gate

Bridge

San Francisco, CA

Suspension

bridge

8,981

feet

220 feet

6

Difficult

Fairly

long

(Built in

1937)

$212

million

10th Ave Bridge

Over Mississippi

(Metro area)

Arch bridge

2175

feet

101 feet

4

Difficult

Long

(Built in

1929)

$ 9 million

Stone Arch

Bridge

Over Mississippi

(Metro Area)

Arch bridge

2100

feet

24.4 feet

Bike and

pedestrian trials

Difficult

Long

(Built in

1883)

$15

million

Greenway

Bridge

Minneapolis, MN-

55, Light Rail Line

Cable-stayed

bridge

2,200

feet

20 to 27

feet

Bike and

pedestrian trials

Easy

Fairly

long

(Built in

2007)

$5.2

million

Arthur Ravenel

Jr. Bridge

South Carolina,

crosses

Cooper River

Cable-stayed

bridge

13,200

feet

186 feet

8

Easy

Fairly

long

(Built in

1929)

$ 62

million

John E.

Mathews

Bridge

Florida,

crosses St. Johns

River

Truss bridge

7736

feet

152 feet

4

Difficult

Short

(Built in

1953)

$ 65

million

Eagle Point

Bridge

Iowa

Truss bridge

2,000

feet

70 feet

2

Difficult

Short

(Built in

1902)

$2.5

million

39

Hennepin Ave Bridge, Minneapolis, MN (Suspension Bridge)

40

Golden Gate Bridge, San Francisco, CA (Suspension Bridge)

41

10th Ave Bridge, Minneapolis, MN (Arch Bridge)

42

Stone Arch Bridge, Minneapolis, MN (Arch Bridge)

43

Greenway Bridge, Minneapolis, MN (Cable-stayed Bridge)

44

Arthur Ravenel Jr. Bridge, Charleston, SC (Cable-stayed Bridge)

45

John E. Mathews Bridge, Jacksonville, FL (Truss Bridge)

46

Eagle Point Bridge, Dubuque, IA (Truss Bridge)

47

Appendix

48

Pre-Post Test for Bridge Activities

Source: KNEX Teacher Guide

Student Name:…………………………………………………..

Date:

1. Answer the following questions.

• What is engineering?

• What do civil engineers do?

2. Match the words with their correct definitions. Draw a line from the word to its matching

definition.

Beam Vertical support that hold up the bridge

Piers Foundation on which roadway/walkway is built on top of the beam.

Span: Distance between the piers

Deck: Horizontal framework that rests on piers

49

3. Match the pictures of different bridges with their names. Draw a line form the name of the

bridge to its matching diagram.

Beam Bridge

Truss Bridge

Arch Bridge

Suspension Bridge

Cable-Stayed Bridge

50

4. Here are some statements about beam, truss, arch, suspension, and cable-stayed bridges. Determine if they are true or false.

--------------- 1. All suspension bridges have three things in common: two very tall towers; strong anchorages; cables made of many wires.

--------------- 2. Cable-stayed bridges easily spans distances under 3000 feet (1000 meters).

-------------- 3. The longer the suspension bridge, the shorter the towers need to be.

--------------- 4. Beam bridges easily span short distances.

--------------- 5. Beam bridges allow large ships to pass underneath.

---------------- 6. Truss bridges span long distances.

---------------- 7. The force that has the most impact on arch bridges is compression.

51

5. Below are facts about the different types of bridges you have investigated. Match the fact with the name of a bridge from the list provided. You may use the bridge names more than once.

ARCH BEAM TRUSS SUSPENSION CABLE-STAYED

1. Because bridges like me are long, light in weight, and high in the air, our greatest enemy is the wind. _____________________________________________

2. Builders made the original versions of me out of wedge shaped stones that fit snugly

together. They were held in place with the pressure of the weight of the bridge.

3. My bridge design is popular when the span is less than 3,000 feet (1,000 meters), mainly

because I do not need anchorages or many piers. _______________________________

4. In the past I was commonly used to cross narrow distances like small streams or rivers. _______________________________________________

5. The strength of my design lies in the use of triangles. ____________________________

6. I am a new bridge design that includes elements from a suspension bridge, I am easier to build than either of those but I am limited to spanning shorter distances. ______________________________________________________

7. Two bridges that are like me are the Brooklyn Bridge and the Golden Gate Bridge. They

both have decks that hang from cables made of hundreds of steel wires. ____________________________

8. I am one of the oldest and simplest bridge designs. Today I can be quite a complex

bridge, but like my ancestors, I support my own weight and the loads I have to bear, on vertical piers. ________________________________________

52

Pre-Post Test for Bridge Activities Answer Key

1. Answer the following questions.

• What is engineer/engineering?

Engineer/Engineering: A person who uses his/her creativity and understanding of

materials, tools, mathematics, and science to design things that solve problems for

people.

• What do civil engineers do?

Civil engineering is a branch of engineering that concern with design of bridges,

highways, buildings, airports, factories, and so on.

2. Match the words with their correct definitions. Draw a line from the word to its matching

definition.

Beam Vertical support that hold up the bridge

Piers Foundation on which roadway/walkway is built on top of the beam.

Span: Distance between the piers

Deck: Horizontal framework that rests on piers

53

3. Match the pictures of different bridges with their names. Draw a line form the name of

the bridge to its matching diagram.

Beam Bridge

Truss Bridge

Arch Bridge

Suspension Bridge

Cable-Stayed Bridge

54

4. Here are some statements about beam, truss, arch, suspension, and cable-stayed bridges. Determine if they are true or false.

----------T---- 1. All suspension bridges have three things in common: two very tall towers; strong anchorages; cables made of many wires.

------------T--- 2. Cable-stayed bridges easily spans distances under 3000 feet (1000 meters).

-----------F--- 3. The longer the suspension bridge, the shorter the towers need to be.

-------------T-- 4. Beam bridges easily span short distances.

------------F--- 5. Beam bridges allow large ships to pass underneath.

-------------F--- 6. Truss bridges span long distances.

--------------T-- 7. The force that has the most impact on arch bridges is compression.

55

5. Below are facts about the different types of bridges you have investigated. Match the fact with the name of a bridge from the list provided. You may use the bridge names more than once.

ARCH BEAM TRUSS SUSPENSION CABLE-STAYED

1. Because bridges like me are long, light in weight, and high in the air, our greatest enemy is the wind. __________________SUSPENSION______________

2. Builders made the original versions of me out of wedge shaped stones that fit snugly

together. They were held in place with the pressure of the weight of the bridge. ARCH

3. My bridge design is popular when the span is less than 3,000 feet (1,000 meters), mainly

because I do not need anchorages or many piers. _CABLE-STAYED________________

4. In the past I was commonly used to cross narrow distances like small streams or rivers. _______________________________BEAM________________

5. The strength of my design lies in the use of triangles. __TRUSS____________________

6. I am a new bridge design that includes elements from a suspension bridge, I am easier to build than either of those but I am limited to spanning shorter distances. ______________ CABLE-STAYED __________________________

7. Two bridges that are like me are the Brooklyn Bridge and the Golden Gate Bridge. They

both have decks that hang from cables made of hundreds of steel wires. __________SUSPENSION_________________

8. I am one of the oldest and simplest bridge designs. Today I can be quite a complex

bridge, but like my ancestors, I support my own weight and the loads I have to bear, on vertical piers. ___________BEAM_____________________________

56

Glossary

Source: www.dot.state.mn.us/

Abutment: Earth-retaining structures supporting the superstructure at each end of the structure. Deck: The bridge floor; the surface that supports the vehicular traffic. Main span: The center or primary span of the bridge over the river, typically the longest span of the bridge. Pier: A vertical structure that supports the bridge superstructure. Piers transfer forces from the superstructure to the foundations. Span: Section of superstructure between supports. The span is the length between supports. Substructure: All portions of the structure below the bearings (pylon, piers, columns, and foundations) that support the superstructure. Superstructure: The top portion of the structure that vehicles drive over, which is supported by the substructure. Tendon: Steel strands used for post tensioning. Tension: A force that is used to stretch (stress) tendons. Transverse: Used to describe the axis of a bridge that lies perpendicular or radial to the longitudinal axis. Vertical Curve: Curvature of the roadway or bridge in the vertical plane.

57

Reference Materials

Books:

Design it! Engineering in after school program (2002), Kelvin, Education Development Center, Inc., NY. K’NEX Education, Teachers’ Guide, Bridges (2007), PA. Internet Resources:

Minnesota Department of Transportation http://www.dot.state.mn.us/ Building Big http://www.pbs.org/wgbh/buildingbig/bridge K’NEX http://www.knex.com/ West Point Bridge Designer www.bridgecontest.usma.edu

http://iti.acns.nwu.edu/links/bridges/disasters.html

http://eduspace.free.fr/bridging_uerope/disasters.html

http://www.engr.utexas.edu/wep/COOL/AcifRiver/allaboutbridges_Disasters.html

http://www.lib.washingtom.edu/specialcoll/tnb/

http://www.ketchum.org/brdigecollapse.html