Bridges and Structures

Lynne Hookstadt

Las Colinas School

Unit Objective

Target Students: An Advanced Science Elective Class, Science Club or GATE activity.

Overview: Unit provides the students with extensive hands on structural design, fabrication and test of building structures. The culminating projects include the design, fabrication and test of a toothpick bridge and a computer generated bridge design and competition.

Technology usage: The students utilize the computers for research, virtual bridge design challenges, and bridge design competition software.

Standards: California 8^th Grade Physics Standards 2 a, b, d

Motivators

Bill Nye Video “Structures”

Paper tower Challenge (Requirement Overhead Appendix)

Internet Activites

Research Worksheet #1 (2 sides)

Building Big - Bridge Basics http://www.pbs.org/wgbh/buildingbig/bridge/basics.html

Labs http://www.pbs.org/wgbh/buildingbig/lab/index.html

Research and Design Challenge Worksheet

Research

How things work. http://www.howstuffworks.com/bridge.htm

Super bridge http://www.pbs.org/wgbh/nova/bridge/

Design Challenges

Super bridge http://www.pbs.org/wgbh/nova/bridge/

Craggy Creek http://www.pbs.org/wgbh/buildingbig/bridge/challenge/index.html

Earthquake http://www.newbaybridge.com/classroom/

Bridge Design Internet Competition – Incredible site!!!

Free Downloadable bridge construction software http://bridgecontest.usma.edu/download.htm

Practice with 2003 software

Compete in the 2004 Challenge

Hands-On Structure Activities

Straw Shapes Activity (straws, paper clips)

Website http://www.pbs.org/wgbh/buildingbig/educator/act_straw_ho.html

Suspension Bridge(straws, dental floss, paper clips, cup, pennies)

Website http://www.pbs.org/wgbh/buildingbig/educator/act_suspension_ho.html

Spaghetti Arm

Requirements Overhead Appendix

Column activity

Website http://www.pbs.org/wgbh/buildingbig/educator/act_index.html

Index Card

Website http://www.exploratorium.edu/science_explorer/card_bridge.html

Toothpick Bridge Design, Fabrication and Test

Requirements website http://branches.asce.org/suncoast/bridgerulesp1.pdf

Class modifications “Appendix”

1^st Place Held 291x its weight

Strength Of Materials Lab

Lab sheet attached

Other Activities

Paper Bridge(paper, paper clips, pennies)

Website http://www.pbs.org/wgbh/buildingbig/educator/act_paper_ho.html

Super Bridge – PBS Noodle, tape, coffee can

Website http://www.pbs.org/wgbh/nova/teachers/activities/2416_bridge.html

Appendix

Page Contents

1 Paper Tower Challenge Requirements: Overhead

2,3 Research Worksheet #1 (2 sides)

4 Research and Design Challenge Worksheet

5 Spaghetti Arm Challenge Requirements: Overhead

6 Toothpick Bridge

7,8 Structure of Material Lab

9 Additional websites

Paper Tower Challenge

Based on Magic Mountain Physic’s Day Challenge (Record ~ 2.6 meters)

Task:

Construct a free standing tower of maximum height using a singe sheet of paper.

Materials:

1 sheet duplicator paper

50 cm clear tape

scissors

rulers

Requirements:

1. 40 minutes to complete this activity

2. Sheet of paper may be cut into pieces and reassembled as desired. Parts may be rolled, folded or split.

3. Tape is to be used to fasten parts of the tower together. It may not be used to attach the tower to the floor or any other object. Excess tape may not be used to extend the height of the tower.

4. A tower shall be declared free standing if it remains self-supported for more than 10 seconds.

5. The highest tower will be declared the winner.

6. If a team decides to build its tower higher after being officially measured, only one additional height will be measured.

7. Notify the teacher when your team is ready for an official height measurement.

8. Name your tower. Make a sign out of a supplied 3 x 5 index card.

Think ahead. No additional materials will be provided.
Bridge Building Research Part 1 (Side 1)

http://www.pbs.org/wgbh/buildingbig/bridge/index.html

Vocabulary

beam __________________________________________________________________________

__________________________________________________________________________

piers __________________________________________________________________________

__________________________________________________________________________

span __________________________________________________________________________

__________________________________________________________________________

force __________________________________________________________________________

__________________________________________________________________________

live load __________________________________________________________________________

__________________________________________________________________________

dead load __________________________________________________________________________

__________________________________________________________________________

tension __________________________________________________________________________

__________________________________________________________________________

compression __________________________________________________________________________

__________________________________________________________________________

torsion __________________________________________________________________________

__________________________________________________________________________

Bridge Basics

Type of Bridge	Describe	Span limitations	Illustrate and label the forces

Check the “Forces Labs” computer labs/simulations and note interesting facts or observations below.

Forces

1. __________________________________________________________________________

2. __________________________________________________________________________

3. __________________________________________________________________________

4. __________________________________________________________________________

5. __________________________________________________________________________

Bridge Building Research Part 1 (Side 2)

Loads

1. __________________________________________________________________________

2. __________________________________________________________________________

3. __________________________________________________________________________

4. __________________________________________________________________________

5. __________________________________________________________________________

Materials

1. __________________________________________________________________________

2. __________________________________________________________________________

3. __________________________________________________________________________

4. __________________________________________________________________________

5. __________________________________________________________________________

Shapes

1. __________________________________________________________________________

2. __________________________________________________________________________

3. __________________________________________________________________________

4. __________________________________________________________________________

Check out 2 Bridges From “Wonders of the world databank” complete the noted information

Bridge 1

Name: _____________________________ Location: ______________________________
Completion Date: _____________________
Type: __________________________ Length: _________________________
Purpose: ________________________
Materials: __________________________

Interesting fact: ___________________________________________________________________________

________________________________________________________________________________________
Design Challenges:_______________________________________________________________________ ________________________________________________________________________________________ ________________________________________________________________________________________
________________________________________________________________________________________

Bridge 2

Interesting fact: ___________________________________________________________________________

________________________________________________________________________________________

Bridge Building Research and Challenges

Bridge Research

General info http://www.howstuffworks.com/bridge.htm

List 6 interesting facts.

1. __________________________________________________________________________

2. __________________________________________________________________________

3. __________________________________________________________________________

4. __________________________________________________________________________

5. __________________________________________________________________________

6. ____________________________________________________________________

Super Bridge http://www.pbs.org/wgbh/nova/bridge/

Research the strengths and weaknesses of the following bridges

Bridge Type	Strengths	Weaknesses
Arch
Beam
Suspension
Cable stayed

Internet Bridge Design Challenges

Super Bridge http://www.pbs.org/wgbh/nova/bridge/

Location 1: 5,000 ft span across an ocean bay ________________________

Location 2: 120 ft span across a freeway ________________________

Location 3: 1000 ft span across a river ________________________

Location 4: 700 ft span across a canyon gorge ________________________

Building Big http://www.pbs.org/wgbh/buildingbig/bridge/challenge/index.html

Craggy Creek – Design Challenge: State the correct bridge for each location.

Location 1: Multi-lane Bridge for commuters and tourists ______________________________

Location 2: Footbridge across a stream ______________________________

Location 3: Highway bridge across a busy shipping port ______________________________

Location 4: Railroad bridge in a national park ______________________________

Earthquake design http://www.newbaybridge.com/classroom/

1. Design a bridge to withstand an earthquake. Test the bridge for both faults and various earthquake magnitudes.

2. Printout the your final design. Identify the fault and level of earthquake magnitude. Attach to this worksheet.

Spaghetti Arm Requirements

Objective

Construct a long spaghetti arm.

Materials

50 Sticks of spaghetti

60 cm of tape

Requirements

Arm will be taped to a table

No other external support

End of arm must not touch the floor

Measurement

Length of the free arm

Toothpick Bridge Requirements - Clarifications

Requirements website http://branches.asce.org/suncoast/bridgerulesp1.pdf

Additional clarifications and/or modification

1. Students worked independently.

2. Students designed their bridge design on drafting paper prior to fabrication.

3. Fabrication took about 10 class periods(50 min.each) to construct the bridge.

4. Square toothpicks were used, more uniform.

5. Carpenters glue works wonderfully, very little glue is needed.

Test Set up:

Load platform

o 8” x 8” ½ inch plywood

o Drill holes in each corner.

o Hang rope and bucket below

o Use disconnect hooks for easy mount to bridge

Load Material

o Initial load of 5 pounds (board, rope, hooks, bucket, sand)

o Sand is added to the bucket until the bridge fails (cannot hold the load)

o Entire load is measured

Bridge spacing

o Level smooth surfaces for the two ends of the bridge.

o 12 inch spacing for all bridges

2003 Results

o 1^st Place 291x its own weight

o 2^nd Place 146x its own weight

o 3^rd Place 128x its own weight

o Balance of the bridges (exceeding the minimum 5 pound load requirement) held between 56x – 122x its own weight.

Strength of Materials Lab

Investigate the strength of various materials.

Test Materials (per team)

2 0.9 mm Pencil Lead 2 7 cm stirring straw section

2 Square toothpicks 2 Plaster bars (fabricated below)

2 7 cm skewer section 2 Plaster bars with screen fabric (fabricated below)

1 7 cm drinking straw section 2 7 cm spaghetti section

2 7 cm steel wire (19 gauge)

Test apparatus (per team)

1 support “hole” approximately 5 cm in diameter

1 large cup or small bucket

1 wire to loop over the test specimen and attaching to the cup/bucket

1 digital balance

1 foam flower block for plaster molds

1 rectangular object (approximately 1 cm x 7 cm x 0.6 cm)

1 box plaster of paris

1 screen fabric (6 cm x 9 cm)

? sand

Procedure

1. Prepare plaster test samples.

a. Prepare a plaster mold for the 6 test samples by depressing the rectangular object into the foam

block.

b. Test samples without screen fabric

· Prepare a small amount of plaster and completely fill 3 molds.

c. Test samples with screen fabric

· Cut 3 pieces of the screen fabric to fit across the inside of the mold.

· Prepare a small amount of plaster and completely fill 3 molds.

· Add a small amount of plaster to the bottom of the remaining 3 molds.

· Layer a piece of screen fabric on top of the plaster

· Fill the remaining mold with plaster completely covering the screen

d. Let the plaster sit for 1 day.

e. Remove the plaster test specimens from the molds.

f. Inspect the specimens and choose the two best/uniform specimens of each type.

2. Test apparatus

a. Set up a test stand that will facilitate suspending a test load from the test samples. The spacing from

each support should be 5 cm apart.

b. Using the wire and cup, build a hanging test load “bucket”.

3. Test procedure

a. Predict the rank of the test specimens, 1 – lowest, 9 - highest

b. Position each specimen over the hole or gap between the supports.

c. Hang the loading “bucket” from the top/center of each specimen.

d. Add sand to the “bucket” until the specimen fails. (can no longer hold the load)

e. Measure the mass of the bucket and sand.

f. Repeat for the remaining specimens.

g. Record all data in the data table below.

h. Re rank the test specimens based on the test data.
4. Data Table

Test Specimen	Specimen #1 Breaking load (g)	Specimen #2 Breaking load (g)	Average Breaking load (g)	Rank Prediction 1-low, 9-high	Rank Actual 1-low, 9-high
Pencil lead
Square toothpick
Wood skewer
Drinking straw
Steel wire
Stirring straw
Plaster bar w/o screen
Plaster bar w/screen
Spaghetti