Post on 08-Jul-2018
transcript
Timite 1
Building a Bridge
Formal Lab Report
By
Ladji Timite
Physics Mr.Jonathan
Ellis Preparatory Academy January 16, 2015
Timite 2
Ladji Timite Physics December 2014
Introduction
My thesis is that a Suspension Bridge is well suited to build for crossing the Hudson
River in the New Paltz area. The purpose of my project is to create a bridge that is most
suitable to cross the Hudson River near New Paltz, New York. I am designing this bridge to ease
congestion in the area, also create a pathway that make it easier to cross the Hudson river, and
help the traveling in that location save time by traveling from one side to the other side of the
Hudson River. In this project we will be talking about two main forces that are apply on our
bridge. Compression is a pushing force that pushes from both end of an object, causing it to
contract on itself. Tension is a pulling force that pulls an object from both end, causing a level of
strain depending on how much the object is being pull.
Some geographic features in the area, New Paltz near Hudson river, is that the area has
high cliffs which makes it difficult to build bridges just on the Hudson river, but instead all the
way over the cliff, making the bridges longer. Some historical facts about the village of New
Paltz is that it was founded in 1678 by French Huguenots who had taken refuge in Mannheim,
Germany, for a few years before coming to America because of the war. (Welcome to Village of
New Paltz.) Also there is a Suspension Bridge name MidHudson bridge open august 25, 1930,
the length of the bridge is 910m and was made to make it easier to cross the long river to the
other side of Hudson River. (MidHudson Bridge.) The actual length of our bridge is 727m long;
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we found it by searching the location on Google Maps, and then measured the width of the
Hudson River using the scale factor of the site. The scale factor was 2.2 cm correspond to 500
Ft., which when we calculate it was 2386.36 Ft. Then cover it into meters which is 727.36 m.
The different types of bridges that I could have chosen for my project were an arch Bridge, a
Truss bridge, and a suspension bridge. The similarities between the suspension bridge and truss
bridge is that they both can be built for a long distance purpose. Also, both have tension and
compression forces applying on them, but suspension bridges are not made for windy areas,
which can be recall of the Tacoma Narrows Bridge. This bridge was self existed because of the
change of pressure cause by the wind, making it twisted on itself and collapse. ( Introduction
UW Libraries). Arch bridge are usually not made for long spans, is its curved design, which does
not push load forces straight down, but instead they are conveyed along the curve of the arch to
the supports on each end. These supports carry the load of entire bridge and are responsible for
holding the arch in the precise position unmoving position. "Arch Bridge Types of Arch
Bridges." Arch Bridges. Suspension Bridge is to be more appealing to the public while the truss
is made to withstand heavy payload. My decision of picking the suspension bridge is the best
because it covers the long area need to cross the Hudson river, during the year there is not that
high of wing. Thus the platform will not be unstable because of high wind like the Tacoma
Narrow Bridge. In final it need to be appealing to attract visitors and will help the economy of
New Paltz.
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1. Experimental Design
By building our model bridge, it will give us evidence to demonstrate that it a suitable
bridge for the Hudson River near New Paltz. By being able to reach a certain length that should
be equivalent to the width of the Hudson River. Second, it has to be able to withstand a certain
amount of payload; in addition the platform must be at a definite width, towers height, the height
between the platform and the river, and all using 10 manila folders to make it. Those requirement
where:
A. The Suspension bridges must be at least 40 cm between their pillar supports.
B. The bridge platform must be at least 10 cm wide.
C. The bridge platform or its structure must be at least 15 cm above the table.
D. Finally, the finished bridge must be able to support a total weight of 45 Newtons (4.588
Kg)
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The plan on building a suspension bridge, specifically a cablestayed bridge with the
length of 2500m with a span of 1500 m, and a tower with a height of 100 m. For the model we
planned to use ten manila folders and strings of the cables, and for the real bridge of course we
will use some type of metal and steel to build it. Some variable we could have change are the
material we used to build our models, like instead of making it with manila folders we could
have used cardboard or popsicle sticks. This will help us have a better understanding of the
solidity of the bridge and a clear view of forces acting on it like tension, shear, and compression.
Also raise the amount of weight, to be comparable to the real weight applied to a real bridge. We
found information to help build our bridge by doing an experiment. Its purpose was to research
how the thickness of the platform on a bridge helps hold heavy payloads. We used manila folders
to make the deck, as well as to tape each end on a desk and adding the way on it. The way we
calculated it was, for each time we add a new platform on top of the old ones, we see how much
deflection it reduces compared to a single platform. At the end of the experiment we found that
the minimum amount of thickness on the bridge, was 10 manila folders to hold 45 newtons of
weight. Additionally, we used website link on www.ellisprepphysics.blogspot.com that Mr.
Jonathan made to understand our bridges and how to build it. The steps we have taking in
building our bridge was to build our towers first, because we thought that it was the most
difficult task in building our model bridge. My partners designed the tower with some paper and
we discussed the good and bad about it, then we started to build them each out of two manila
folders. Secondly, we started to build the deck with the information we got from our experiment,
which is increasing the thickness of the deck with six rectangular shapes cut out of the manila
folders. Finally adding the cable of the suspension bridge, in which we use strings that go on top
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of tower and through two holes in the platform in each side. Some bias we had was that if we
added columns or a truss bridge structure in the towers, it would make it even stronger, and
prevent the whole bridge from binding to one side, also if we have more materials (manila
folders) it would have been completed.The actual length of our bridge is 762 meters long; I
calculated with the ration in Google map the width of the Hudson River, which is 2 cm, is equal
500 feet. Therefore I measure the width of the Hudson River which was 10 cm,
. Then convert it into meter which is 727.36 m. "Google Maps."Google 386.36 ft2.2 cm10 cm ×500 f t = 2
Maps. N.p., n.d. Web. 30 Dec. 2014.
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2. Data
Y= mean deflection R2= The equation in that graph R2= 0.94399 represent how accurate the information in the graph is, the closer it is to one, the more reliable those information are.
Class Average Data
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The deflection of the manilla folder
Number
of folders
Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 Average
1 1.5 cm 2.8 1.4 1.1 2 2.2 1.8
2 1cm 2.4 1.2 0.9 1.5 2 1.5
3 1 cm 1.9 1.3 0.8 1 1.8 1.3
4 1.2 cm 1.6 1.3 0.5 1 1.5 1.1
5 1.1 cm 1.4 1.2 0.5 1.1 1.3 1.1
6 1 cm 1.2 1.5 0.4 1 1.1 1.0
7 1 cm 1.1 1,.4 1 0.9 1 1.0
8 1.1 cm 1.0 1.3 1.1 1.1 0.8 1.0
9 0.9 cm 0.8 1.3 1.3 1.1 0.6 1
10 1 cm 0.6 1.2 1 1 0.4 0.8
In the final analysis our bridge was able to hold a weight of 45 newton, however the
support were binding. This mean that my group need to make a stronger tower by changing the
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design in order to distribute the compression force that apply on it through the cables. Also the
deck were binding in the middle, no because of the thickness of the bridge, but because there
wasn’t much support from the cables. We only made two holes in each side of the bridge,
specifically in the middle of bridge. This creates too much tension for the strings to hold and also
lead to a greater amount of compression in the tower, another reason why the towers were
binding. For that we need to make more holes along the bridge to distribute the forces evenly.
3. Analysis
Based on my results, I still think that our bridge is the most suitable bridge, even though
the deck bended from the weight. First because of the MidHudson that was build in the area
next to where I plan to build my bridge, this show that the suspension bridge is a logical choice
to be build there. Also according to the number of folder and class average graph seen
previously, we should have use a 10 manila folders for the deck, but with the limited materials
we only use 6 instead. The equation in that graph R2= 0.94399 represent how accurate the
information in the graph is, the closer it is to one, the more reliable the information. For this
reason using 10 manila folders would have been the logical choice to hold 45 newtons, but the
limited material would not allow us. Therefore we used six folders to build our platform. Also
there was not much support from the cable to distribute the weight around the bridge, and this
was the reason why our bridge had much deflection in the middle of the deck, but did not fail. In
addition, our towers were not well structure to hold the weight of 45 newton. Thus for the next
model we should use 10 manila folder instead of 6 for the platform, create more cable support
the deck, and make stronger towers.
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This connected to our background research about forces that are apply on a suspension
bridge, meaning that my group need to make a stronger tower by changing the design in order to
distribute the compression force that apply on it through the cables. Also the deck were binding
in the middle, no because of the thickness of the bridge, but because there wasn’t much support
from the cables. We only made two holes in each side of the bridge, specifically in the middle of
bridge. This creates too much tension for the strings to hold and also lead to a greater amount of
compression in the tower, another reason why the towers were binding. For that we need to make
more holes along the bridge to distribute the forces evenly.
4. Revisions
Something that I will change to minimize the experimental errors and effect of bias are
the structure of the Towers. If possible our group will change the hollow towers with solid and
heavy ones that will make it strong and stable. In other words it will prevent the tower from
binding and make it unwavering, also keep the deck from falling out of the towers. Another
change that I would suggest my group to do is add multiple cable supports from each side and
along the way of the bridge. This will make the deck more steady and hopefully not bind while
under a certain weight. Furthermore, this would spread the force of tension in the multiple cables
and convert it to compression on the solids Tower to withstand. In addition, a variable we could
have change are the material we used to build our models, like instead of making it with manila
folders we could have use cardboard or popsicle sticks instead to make more realistic, and get
better data from it.
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A new question that I have about designing bridges is by adding more cables support on
the deck, will it apply less compression forces to the Towers or not? Another question I have is,
how can I implant a truss bridge structure to my towers in order to strengthen and steady them?
Those question are important because they will provide useful information to use in the next
model that my group might make if we get the chance to.
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Bibliography
"Welcome to Village of New Paltz." Http://www.newpaltzvillage.org/home/. Copyright © 2014
The Village Of New Paltz, n.d. Web. 17 Dec. 2014.
MidHudson Bridge (US 44 and NY 55)." MidHudson Bridge (US 44 and NY 55). N.p., n.d.
Web. 17 Dec. 2014.
Arch Bridges. Copyright© History of Bridges, n.d. Web. 18 Dec. 2014
<http://www.historyofbridges.com/factsaboutbridges/archbridges/>.
"Introduction." UW Libraries. N.p., n.d. Web. 13 Jan. 2015.
<http://www.lib.washington.edu/specialcollections/collections/exhibits/tnb>.
"Google Maps." Google Maps. N.p., n.d. Web. 30 Dec. 2014.
<https://www.google.com/maps/place/New+Paltz,+NY+12561/@41.75103,74.0396433,12z/d
ata=!4m2!3m1!1s0x89dd1884bdee8f8d:0x82c17e4b65e32b6f?hl=en>