Our hypothesis is that if we test 3 different bridge designs that based on our research about the structure and history of the bridges then we think the suspension bridge will hold the most weight.

Our project is to test three different types of bridges, and see which one can hold the most weight through popsicle sticks put together with hot glue and for suspension cables we will be using yarn.

For our project our manipulated variable will be the design of the bridges that we use.

When we change the design the responding variable will be how much weight the different designs can hold in comparison to each other.

A suspension bridge can hold 10s of thousands to 100s of thousands of tons, depending on its size and material. Beam bridges can hold a few tons, while bigger ones meant for heavier traffic can hold 100s of tons. Arch bridges can hold a few to several thousand tons depending on many factors.

The earliest version of the suspension bridge was created by Thangtong Gyalpo.  The first suspension bridge was built in the 15th century in Tebat.  He built over 58 iron chain suspension bridges and 1 survived until 2004 when it was washed away in a flood.  Most of his bridges had chains for suspensions but his earlier designs were made from twisted yak skins and willows.   Ancient Romans created the arch bridge 2000 to 3000 years ago.  When humans started building bridges, they made them in simple forms with cut up wooden logs or planks, stone, with a simple crossbeam and support arrangement, sometimes with use of natural fibers woven together to hold materials.  One of the oldest arch bridges in existence is Arkadiko Bridge in Peloponnese Greece. The first beam bridges appeared in nature prehistoric, humans saw that a tree had fallen across a stream and used the technique in places that it was convenient for them. Herodotus, a historian from Ancient Greece was the first one to leave the written document about the arch bridge in 448 BC.

Beam bridges rely on supports, which can be piers or abutments to bear the load of the beams and transfer it to the ground.  Piers are vertical posts or columns built in the ground or the water, while at the ends of the bridge are the abutments which are solid. Arch bridges are some of the oldest designs of bridges and have been around for thousands of years and have great natural strength. They were originally made of stone or brick but lately they are built from reinforced concrete or steel. The introduction of these new stronger materials allow arch bridges to be longer with lower spans. When weight is put on it instead of pushing straight down the arch carries the weight outward along the curve of the arch to the supports at each end and the weight is transferred to the supports at either end. These supports are called the abutments carrying the load out toward the ends of the bridge and keep the ends of the bridge from spreading out. The weight of the bridge deck and the traffic it carries is transferred to vertical cables called suspenders. The suspenders are attached to the main suspension cables, the prominent, curved cables that drape between two tall towers. The main cables are in a state of tension, a pulling force, as they carry the immense load of the deck and the traffic. This tension in the main cables is transferred to the anchorages and towers . The towers are under compression, meaning the force of the cables pushes directly down on them, transferring the load of the deck and traffic into the ground. To counteract the horizontal pull of the main cables, massive anchorages are made at the ends of the bridge. These are giant blocks of reinforced concrete embedded deep into solid rock or ground, resisting the inward pull from the cables.                For the arch bridge we are using the Rocky Creek Bridge as our example to make. For the beam bridge we are using The Sluppen Bridge. For the suspension bridge we are using The Golden Gate Bridge as our example.

It is important to know which bridge designs are stronger because if you put an arch bridge where suspension bridges are it probably won't be able to hold enough weight because of the distance and heavy traffic, so then it could collapse but if you know that it wont hold that much weight before you put it up then it would save a lot of time, money and if people were on it when it collapsed then it would save lives too.

Some sites we have used while making our research page were: Historyofbridges.com Teacherscollegesj.org landing.midasaser.com design-technology.org wikipedia.org thetouristchecklist.com

Control variable: Material used, it is something that must stay the same throughout the experiment.

Manipulative variable: The thing you change to properly test it.

Responding variable: The answer to your question/the out come of the test.

Procedure

Rocky Creek Arch Bridge.

First for building the Rocky Creek arch bridge you have to get out your cardboard platform and plug in your hot glue gun, then get your reference picture. Then you start building the end supports, first stack eight, one wide popsicle sticks flat going up, then thirteen trimmed ones on top of that (do that twice so you have two end supports.) Next you will start making the arch by gluing three doubled popsicle sticks, one wide, at three different angles so they form the shape of an arch, (make two of the arches.). Once you have both of your arches make four connecting doubled supports, one popsicle stick wide, spaced evenly in between the two arches. Then you glue the two connected arches to the end supports where they meet the floor. Then you glue twelve supports doubled, one stick wide, standing up straight on the arch at various heights so that they all meet at the height of the two end supports, (Do six on both sides of the arch.). Now you will make the road for the bridge by making an under layer and an over layer facing different directions, just longer than the two end supports (almost two popsicle sticks past the supports on the side and half a stick going past the supports at the end.), each layer one popsicle stick thick, the top layer is ten wide and the bottom layer is seventeen wide. Then you will glue both layers pf the road to the supports. Lastly you will add four popsicle sticks on their side and at the end of the road for railings and you are all done.

Sluppen Beam Bridge

First for the Sluppen beam bridge your cardboard platform and plug in your glue gun, then get your reference picture. For the beam bridge you have to stack fifteen popsicle sticks and do that three times to make the supports. Glue them to your cardboard platform about two inches apart from each other, there should be two supports at both ends and one support in the middle. Then add three little supports laid out flat on the supports evenly spaced, they should two to three sticks thick. Now you will make the road by making an under layer and an over layer facing different directions, just longer than the two end supports (almost two popsicle sticks past the supports on the sides and half a popsicle stick going past the supports at the end.), each layer one popsicle stick thick. The top layer is twelve wide and the bottom layer is twenty wide. Then you will glue both of the road layers to the supports. Lastly you will glue four popsicle sticks on their sides at the end of the road as railings.

Clifton Suspension Bridge

First for the Clifton suspension bridge you have to get out your cardboard platform and plug in your glue gun, then get your reference picture. For the suspension bridge you will start by making six panels that are one popsicle stick thick, that form a rectangular prism when you glue them together, but before gluing the top on the rectangular prism on you have to make two sticks forming a triangle inside the rectangular prism, (make them two or three sticks thick.). Make sure that the triangle formed sticks in the rectangular prism are level with the walls since they are supports, then you can glue the top on. After you have your two rectangular prisms you can glue them about three to four inches apart. For the road you will make an under layer and an over layer facing different directions, just longer than than the two end supports (almost two popsicle sticks past the supports on the sides and half a stick going past the supports at the end.), each layer is one popsicle stick thick. The top layer is twelve wide and the bottom layer is twenty seven wide. Then you will glue both of the road layers to the end supports. Now you will make two upper supports by gluing two popsicle sticks together that are three stacked. You will glue them together by making a platform two to three thick at the top so when they are all glued together it will form the shape of a triangle with a platform at the top. Then you will make another platform similar to the top platform but it will go in between the triangle shape, the platform will also be two to three sticks thick. Make two of those. In the end you should have two pillars that look like the letter A. Next you have to use a box cutter to cut the road about an inch long in the middle of where the rectangular prism supports are, do that on all four sides then you drill brackets into both the A upper supports and the rectangular prism lower supports so they are connected, also add hot glue to the A upper supports so they are stronger. After that you have to wrap air craft cable around the support we put in the middle of the A support, wrap the air craft cables around and connect it at the other side using compression connectors to keep them in place and crimping pliers to crimp the compression connectors together. After that drill eight holes four on each side on the bridge at the second to last popsicle stick from the edge. After you drill those holes you have to feed wire through it and wrap it around the original wire, using suspension connectors every time you wrap the wire around the original wire to properly secure it. Make sure that at the start and the end of the secondary wire you place a compression connector there to keep it secure and doing that makes sure it doesn't come loose. After that you are all done building the Clifton suspension bridge.

Observations

Arch Bridge During the testing of the arch bridge we observed that at around 50-80 pounds the railings broke but we didn't need them for holding any weight, they were mainly just for looks and to keep the design more similar to the reference picture. Around 350-400 pounds we started to hear cracks in the bridge as we stacked more weights on. Then finally at 492 pounds the bridge broke, one side of the arch collapsed under the other arch pieces then the all of the bridge supports collapsed down to the right and flattened.

Beam Bridge During the testing of the beam bridge we observed that also around 50-80 pounds the railings broke, but again they were there for looks not for structural integrity. Like the arch bridge we started hearing cracks but for the beam bridge we started hearing them around 450-500 pounds. Then at 580 pounds the bridge broke. The supports under the beam bridge weren't perfectly straight when we glued them on to the cardboard platform so the more weight we added the more weight was on the slightly off angle of the supports, so the supports collapsed to the right and flattened.

Suspension Bridge During the testing of the suspension bridge we had to use wood blocks to make the weight even on the bridge so the weight would be evenly distributed. At around 200 pounds we started noticing cracks in the road underneath one of the upper supports and the brackets holding the upper supports started to come loose. Then at 280 pounds the upper supports broke off and a chuck of the road came with them, when the upper supports broke the wire also broke with it. The bridge itself didn't collapse like the others but with the upper supports and the wires broken the testing could not go on since those were the parts that made the bridge a suspension bridge.

How hypothesis was wrong, based on out research we thought that the suspension bridge would hold the most weight but because of difficulty levels and unfair testing it was the beam bridge that held the most amount of weight.

The suspension bridge held 280 pounds before the weights and it tipped over to the side and the towers and the base supports broke. That was on its third or fourth time because it was really hard to balance the weight on the suspension bridge.

The arch bridge held 492 pounds before the hole stack just bumped straight down without tipping over as the arch bridge collapsed. That was on its second try because the first time the weights tipped over and we had to try again.

The beam bridge held the most weight at 580 pounds before it just dropped, no weights fell over it just bumped down as the beam bridge collapsed.

Our hypothesis was wrong, based on out research we thought that the suspension bridge would hold the most weight but in the end it was the beam bridge that held the most weight.

The suspension bridge had very unfair testing because the two towers and the suspensions were in the way so we could not put the weight on the road part. Instead we had to get two blocks of wood and stack one on its side on the road and the other on top of that on its face to create a mini platform to balance the weights on. It was really hard to balance the weights on that so it kept tipping over and we had to restack it like three or four times. The level of difficulty has a role to play with how much weight each bridge held because the suspension bridge was really hard to make and complicated so we could not build it exactly ho we were supposed to. The people who designed the bridge knew what they were doing but we do not and we had to improvise a tiny bit because of how complicated and hard it was to build.

The arch bridge was not too hard to build but not to easy, it was the middle difficulty level and it held the middle amount of weight.

The beam bridge was the easiest by far to make, all we had to do was basically some pillars, tiny supports, a road and a railing but even that took a while to build.

Applications

With our experiments, even though they were just miniature models of bridges, I think it can help architects decide what bridges to use and put in certain places. For example the beam bridge held the most weight in our experiments but that doesn't mean people should start building beam bridges everywhere. For crossing large bodies of water suspension bridges would be better, for crossing small bodies of water or a small area of land beam bridges would be better, and for crossing a medium area of land arch bridges would be best. If you don't know where to put the right bridges or if you don't know how much weight they can hold it can be very dangerous. Plus if you build the right bridge the first time if can save materials, time, money, and there wouldn't be any chance of the bridges collapsing, hurting anyone, or causing damage to the land around it.

Sources Of Error

Arch Bridge After the arch bridge broke we saw that one of the pieces of the arch had snapped in half and tipped over to the side going under the other arch pieces since the pieces of the arch bridge weren't at a perfect angle, so if the arch pieces had been at a perfect angle the bridge would have held more weight. Even if the arch pieces didn't brake, we think if the end supports were straighter they would have held more weight instead of flattening to the side. We put popsicle sticks standing up on the arch part of the bridge which helped hold the weight, but I think if we had built a little area for the sticks to sit in it would have been stronger. It could have been a little mold made of popsicle sticks that held the support popsicle stick up instead of just being glued. I think if we also double stacked those same popsicle sticks going straight up, the bridge would have held more weight.

Beam Bridge When the Beam bridge broke and we looked at the remains, we found that the three supports had been pushed to the side and flattened, so if we had made sure that the supports were perfectly straight, then the supports would have no where to go when the weight pressed down on them and then the bridge would have been able to hole more weight. We had the three supports under the bridge as straight lines but if we made them going from thick to thin, thick at the bottom then slowly becoming thinner kind of forming a triangle that would have been able to hold more weight since there would have been more security and structural integrity. If we had combined both of these techniques the beam could have held a lot more weight.

Suspension Bridge The two rectangular prism shaped end supports under the bridge were hollow except for a triangle shaped support inside the rectangular prism, so if we had laid the sticks out flat, layer them to make the same shape it would have been a lot stronger, but we did not have the time for that since it takes a long time to cut all the sticks to shape, glue them together to make a sheet of popsicle sticks, then stack them together who know how many times. We also didn't have enough materials for that since it would have taken around 2-4 bags of popsicle sticks just for the bottom supports. The part of the suspension wires that go through the holes under the bridge are a little loose, we tried to tighten them as much as we could but the wire was pretty stiff so it was difficult, but we think the bridge would have been able to hold more weight of they were tighter. Because the upper supports were in the way we had to stack two blocks of wood on the bridge to evenly distribute the weight, but doing that made the it kind of unfair for the testing and the weight kept falling off the wood, so if we had made the road part of the bridge bigger it could properly hold the weights and be more fair for the testing.

Websites used while making the project. Historyofbridges.com Teacherscollegesj.org landing.midasaser.com design-technology.org wikipedia.org thetouristchecklist.com

Scott (Austin's dad) supervised us when we were putting the brackets on, drilling the holes and gave us an idea of how to thread the wire through the holes, and it was his brackets, screws, drills, air craft cable, wire, compression clips and pliers.

Sheri (Austin's mom) and Candice (Ethan's mom) bought us our building supplies (card board, scissors, pencils, pens, popsicle sticks and cardstock, it was Sheri's hot glue gun that we used, Sheri helped us understand some of what we were supposed to do in our logbooks like variables, conclusion etc.

Sheri thought us how to make the graphs.

Acknowledgments

During the building of the bridges and all of the science fair in general we got help with the project. Austin's mom (Sheri) and Ethan's mom (Candice) bought the materials.

Austin's dad (Scott) helped come up with the ideas on how to build the suspension part of the suspension bridge, and he helped with drilling and finding materials.

Austin's mom (Sheri) helped with the graphs for the data management section in our science fair binders.

Austin's parents and my parents gave us the cardboard platforms, and finally Austin's parents gave us the hot glue, hot glue gun, scissors, wires, brackets, bolt etc.