Science Horizons Lab
Research paper
The results of stress and strain on Bridges
By Kathleen Lott
Table of contents
1. Abstract: Page 1
2. Research Plan: Page 2
3. Introduction: Page 3
4. Materials: Page 4
5. Procedures: Page 5
6. Results: Page 8
7. Project Data Book: Page 9
8. Discussion/Conclusion: Page 14
9. Works Cited: Page 16
Abstract
The purpose of this experiment is to find thorough scientific inquiry which
popular bridge design holds up best against stress in order to identify the best bridge for
use. This essay is the result of stress experimentation on three bridges. The original idea
was to test the bridges that held up best against weight. There was little success with
designs which led to only one of the three showing drastic signs of stress concluding in
the breaking of that bridge.
Resistance to stress was determined by adding 1.360777, 2.35868, 4.48951 Kg
weights one at a time. The making of the bridges consisted of taping, gluing, and carving
pieces in order for everything to fit together and to work as desired. At first things did not
always work out because the bridges sat for 24 hours or more in order to ensure that the
bridges could actually hold their own weight before adding any additional weight.
The suspension bridge and the beam bridge did not have a breaking point,
however the arch bridge had a breaking point at 4.48951 Kg after an average of 1.16666
seconds. In conclusion the bridge that held up best was the beam bridge but the
suspension bridge also showed little signs of stress while the arch collapsed after an
average of 1.16666 seconds with 4.48951 Kg.
Research Plan
The problem being addressed is to find, thorough scientific inquiry, which
popular bridge design holds up best against stress in order to identify the best bridge for
use. My hypothesis is: If two bridges (Deck beam and Arch) are built and tested, then the
Deck Beam Bridge will cope worse with weight compared to the control (Suspension
Bridge). My engineering goals are to find, through scientific inquiry, which design of
bridge will hold up best against stress and strain in order to identify the best bridge for
use. My procedures are adapted to this experiment specifically and will be made and
revised during trial tests. To analyze data I will add the weights, and then I will
observe and record their effects on each bridge. I will also record the amount of
time that is needed to show extreme amounts of strain within 10 seconds.
Introduction
Background: In this experiment I will be testing how different bridges
withstand different amounts of stress and strain. My research was prompted by the recent
bridge failures in this country. I hope to find the bridge design that will stand up best
against the most common forces a bridge would encounter.
Variables:
Independent Variable: Design
Dependant Variable: Weight
Control: Suspension bridge
Purpose: The purpose of this experiment is to find, thorough scientific inquiry, which
popular bridge design holds up best against stress in order to identify the best bridge for
use.
Engineering Goals: To find, through scientific inquiry, which design of bridge will hold
up best against stress and strain in order to identify the best bridge for use.
Hypothesis: If two bridges (Deck beam and Arch) are built and tested then the Deck
Beam Bridge will cope worse with weight compared to the control (Suspension Bridge).
Materials

Computer

Weights(1.360777, 2.35868, 4.48951 Kg)

Duck tape

Scotch maximum adhesive wood glue

Ruler

Meter stick

2, 1.10  30.48 wood rods

24 gauge wire

3, 10’0.5’ 62’ boards

Razor

Small screw driver

6 of the same size boxes

1, 0.1510.160.9 board

124, 5.710.310.31 miniature dowels

Composition book

Pencils with erasers

Glasses

Gloves

Protractor

3, ½ 92 ½ cm rods

Electric screw driver

1 ½ cm blade

Spring scale
Procedures
Procedure for Deck Beam Bridge:
1. Mark the board halfway length wise
2. Mark the board every 2 cm width wise
3. Repeat steps 1 and 2 with other board
4. Count the number parallel lines there are on one side of halfway line
5. Multiply by two to get the total number of lines per one board
6. Multiple this number by two to get the number of dowels needed
7. Glue at a 110 angel in
8. Lining up the middle of each dowel to form an X
9. Let glue dry
10. Take board with lines and tape to two boxes 2 cm in with 18 cm of duck
tape 1 ½ cm over board
11. Use small screw driver to carve small indent into wood on ach side of
the board and two indents in the middle
12. Glue Xs into notches making sure they are upright
13. Let dry
14. Glue along lines on the other board
15. Place on top of board with Xs
16. Let dry
Procedure for Arch Bridge:
1. Cut down rods so that they are 6 cm shorter than the board
2. Make a notch on each side of the rods 1 cm from the edge
3. Space rods 3 cm apart
4. Tape together with 1 cm width 5 cm long piece of duck tape making
sure that notches are facing up
5. Tape to boxes with 10 cm of tape right after the notch
6. Tape on to boards over the previous tape with 10 cm of tape
7. Bend board so it matches up with notches
8. Tape bottom of the boards with 60 cm of duck tape
9. Make sure that the entire edge of the board is covered (3 pieces of tape)
5 cm of tape wrap over each side
10. Add another 14 cm of tape over the overlap of tape
11. Glue board on to rods making using notches as guide glue should drip
onto board as well
Procedure for Suspension Bridge:
1. Measure and mark 1 cm on each end of the board
2. Excluding the 1 cm on either end, measure and mark the board down the
middle
3. Measure and mark half of the newest marks so that the board is divided
into 8ths
4. Cut first 1 ½ cm wide hole on the 1st ¼ and the second on the 3rd ¼
parallel line
5. Cut a 65 cm piece of tape
6. Cut piece of tape into 6, 1cm wide almost ½ way to middle
7. Repeat on other side
8. Push ½ of tape through the hole
9. Spread out tape around edge of hole so it looks like a star
10. Cut 30 cm of wire
11. Attach board to boxes with 15 of tape line edge of box up with the 1 cm
on each side line edge of piece with line
12. Insert pylon into hole
13. Glue in place
14. Let glue dry
Discussion/ Conclusion
Conclusion paragraph 1:If two bridges (Deck beam and Arch) are built and tested
then the Deck Beam Bridge will cope worse with weight compared to the control
(Suspension Bridge). Incorrect.
Conclusion paragraph 2:My hypothesis is incorrect because the deck beam coped
the best with the tests. Looking at the data table, the notes taken during and after the tests
on the beam bridge state that for the most part the bridge showed only small reactions
compared to the other bridges even when the maximum amount of weight was added.
The graph is misleading in terms of observable signs of stress that were not significant
enough to cause the bridge to malfunction.
Conclusion paragraph 3:Some problems that were encountered during testing
were that the bridges were created in a way that allowed only the most visual of their
designs to be recreated in the models. This means that the bridges were only the simplest
of their design with only basic builds. This could have affected the data because if there
were other parts of the inner workings of the bridges then they were most likely over
looked, leaving the bridge in most cases weaker than it would be if made full scale. Other
problems consisted of certain early models broke before testing even though said models
were the most accurate to their real life counter parts. Another problem was that the wood
used for the arch bridge was thinner than the wood used in the other bridges due to the
fact that the wood used in other tests was not flexible enough to bend. This most likely
affected the data because this bridge was far weaker than the others. I suggest using a
combination of the suspension and Deck beam bridges however I do not believe that my
data should be taken into much consideration due to the number of variables added
without meaning. Suggestions to further experimentation on this subject are to find a
better building material that is flexible and yet strong enough to withstand the tests.
Credits: I would like to credit my mother, Mary, for helping me with various parts
of this lab and providing the materials.
Works Cited for Science Horizons Lab
BBC News. N.p., n.d. Web. 6 Nov. 2009. <http:/news.bbc.co.uk/2/hi/americas/6927113.stm>.
“Dynamic response of a curved bridge under moving truck load.” ScienceDirect 24.10: n. pag.
Abstract. ScienceDirect 24.10 (2002). ScienceDirect. Web. 9 Nov. 2009. <http:/
www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2Y-460WGMP3&_user=10&_coverDate=10%2F31%2F2002&_alid=1160156976&_rdoc=80&_fmt=hi
gh&_orig=search&_cdi=5715&_sort=r&_docanchor=&view=c&_ct=1405&_acct=C000
050221&_version=1&_urlVersion=0&_userid=10&>.
“Life-cycle cost-effective optimum design of steel bridges considering environmental stressors.”
Science Direct 28.9: n. pag. Abstract. Science Direct 28.9 (2006): 1. ScienceDirect. Web.
2 Nov. 2009. <http:/www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2Y4JJGB8Y-1&_user=10&_coverDate=07%2F31%2F2006&_alid=1160156976>.
Narayanan, Subramanian, Dr. “I-35W Mississippi river Bridge Failure- Is it a wake up call?”
Structural Engineers Forum of India. N.p., n.d. Web. 5 Nov. 2009. <http:/
www.sefindia.org/?q=node/82>.
The New York Times 2 Aug. 2007: n. pag. Web. 4 Nov. 2009. <http:/topics.nytimes.com/topics/
reference/timestopics/subjects/b/bridges_and_tunnels/bridge_disasters/index.html>.