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Isu presentation:arch bridges

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Kathy Got

on 2 June 2011

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Transcript of Isu presentation:arch bridges

Arch bridges
by Katherine Through arch bridges Under arch bridges Over arch bridges A. The 3 types of arch bridges are: You might be wondering...what is an arch bridge? If this is so, then this presentation is for you. For the first part of this presentation, I have put together some of the questions I had when I was starting to learn about these bridges and answered them. For the second part, I have listed some arch bridges in real life and how they have helped the evolution of this type of bridge. So, let the learning begin!
(P.S. I have highlighted some important words along the way.) Questions I had:
What are the types of arch bridges?
How do you build an arch bridge?
What materials are best when building this kind of bridge?
What forces does an arch bridge have to resist?
What is the future of these structures? Q: What are the types of arch bridges? Q. How do you build an arch bridge? 1. Build bricks out of your chosen material. These bricks are made out of concrete, attached with mortar. 3. Build a wooden centering that will support the bridge during building. 4 Assemble the blocks you made onto the centering. Make sure that there is plenty of tension between the blocks, as this will be the thing that holds the bridge together. To do this, put each brick on top of the previous one so that gravity will pull the stones down and the bridge's load will be transferred horizontally. 2. Make firm supports in the ground, called "abutments". Do this by digging deep into an area of ground and inserting your slabs of stone into it, then building the rest of your stones on top of that. Load being transferred horizontally because of gravity 5. Apply the mortar in between the stones. Let it dry, and then remove the centering. Paint the finished bridge, then let that dry, too. You are now done! Q. What materials are best when building this type of bridge? A. Even though that really depends on the situation, the best types of materials to use are... Steel:
Steel is good because it is not brittle or crumbly and it doesn't rust if you paint it often enough. Concrete:
Concrete is cheap and common. However, it is very crumbly and might break under pressure. Reinforced concrete:
This is the perfect combination of steel and concrete, as this is basically concrete with steel bars stuck inside. It is cheap, but still strong. Q. What forces do arch bridges have to resist? A. The forces arch bridges have to resist are... Weather (rain, hail, heat, natural disasters, storms, snow, ice,etc.) An arch bridge resists this force by having abutments, which pull it to the ground so the wind/ windy weather does not uproot it. Also, the material of the bridge is very important, as we should avoid several kinds to prevent the bridge from getting damaged by the other kinds of weather. Weight (Load). An arch bridge withstands this force by transferring the load horizontally instead of vertically like other types of bridges. The shape of the arch plays a crucial part in this transferring, as it enables the weight to pass stone to stone and finally to the supports in the ground. Without those supports (the abutments), the bridge would not be able to resist all that weight; therefore, it would be squished and flatten out. And Gravity: An arch bridge withstands this force because each stone is placed so that when gravity pulls the stones down, all they do is push down on each other, helping the entire structure to be more stable. Q. What is the future of these structures? A. No one really knows, but here are a few ideas... Arch bridges will be eliminated as a main bridge because people won't build them any more. Arch bridges are very expensive and hard to build, so even though they are effective when it comes to resisting forces, they might disappear. Arch bridges will be made out of new materials, such as several kinds of plastics, to make them less expensive. These materials are currently bring tested to make sure that they are as strong as the ones we have now. When they are done, however, scientists have promised that they will be even more efficient than reinforced concrete. Overall, the concept is very promising. The arch bridge "golden age" will commence. People will finally realise the true potential of arch bridges, and abandon other types of bridges despite of their cost/time to build. Although highly unlikely, this idea is definitely a possibilty, considering the fact that throughout the course of time, arch bidges have remained standing and never failed to please! (Most of the time.) Although this part was very exciting, we must now continue to the next section of our presentation- the famous arch bridges! Here you will get to learn about the most famous bridges of all time- bridges that have shown extraordinary resistence to their forces, bridges that have remained standing for an extremely long time, and the first, last, and longest bridges ever! Let's go! Whoa! Some famous arch bridges:
the first cast iron bridge (Shropshire, England)
the longest arch bridge (China)
the most expensive arch bridge (Dubai) The first cast iron bridge To enable this bridge to withstand it's forces, engineers decided to make it out of cast iron, a material which had previously been too expensive to use for this kind of construction. Since there was no model to follow for this bridge, being as it was the first one of it's kind, the workers decided to base it on carpentry.To ensure the stability of the bridge, they fastened all of the iron pieces together with nuts and bolts, as welding had not yet been invented. This bridge cost a lot, but not nearly as much as the... The longest arch bridge The longest arch bridge is the Lupu Bridge in China. Before the bridge was actually built, the design was disputed among engineers. A cheaper version of the current design was mentionned, but even though it was just as effective when it came to resisting forces, it was rejected because of it's similarity to other long bridges. Although this bridge design was selected, Chinese citizens were not happy because they needed to pay extra taxes to cover the cost of the bridge. Eventually, the mayor who chose the bridge was forced to step down from his reign and carry the title of "disgraced". Most expensive arch bridge Although not yet completed, it is rumoured that this bridge will be the longest bridge as well as the most expensive. Most of the information about it is confidential, but we know that it will be a marvel in the world of arch bridges. I hope you enjoyed this presentation, and learned a lot about arch bridges. Maybe it'll be you who discovers a new way to build them or comes up with a new revolutionary material to build them with! But for now, have fun looking at my other stuff!
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