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Bridge Design (and Destruction!) Part 2
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Bridge Design (and Destruction!) Part 2
In our last video, we looked at the simple designs of beam and arch bridges.
00:00:01
Now let's move into the modern age with the truss bridge.
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Truss bridges make use of a large frame, called a truss, that sits on top or below the bridge deck.
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In this case, it is on top.
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While it may seem like we are only adding weight to the deck,
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the design of the truss distributes the load through the frame so that the deck does not experience as much of a load.
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Each segment of the truss experiences different loads of either tension or compression.
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We apply two equal loads to the deck and calculate the loads in each segment,
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which are shown as percentages of the total load.
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You can see that the largest loads are on the end and top segments,
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while the middle segments have none.
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Remember that when we do the compression test. Spoiler alert!
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Let's see if this convict gets shot out of his truss jail.
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So how do you think the truss will break?
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Discuss.
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Thanks for coming, Yoda. I love your work.
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As you can see, the outer segments of the truss are the first to break
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because they were handling the largest part of the load.
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The diagram showed that the outer and top segments had the same loads.
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Why didn't the top break?
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That's because the top pieces are aligned along the grain of the wood
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and wood is stronger in that direction. Adding the truss allowed the same deck
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length to hold 32 pounds, which is 25% stronger than the beam bridge of the
00:01:56
same length. The final type of bridge we'll discuss is the iconic suspension
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bridge. Although the only suspension bridge around us is less than iconic, but
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the same principles apply. Suspension bridges utilize thick steel cables that
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support the deck and transfer the load to the towers and to the anchors at the end of
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the bridge.
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Supporting cables are used to suspend the bridge deck from the main cables.
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The main cables and supporting cables of the bridge are always under tension.
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The cables transfer the load to the towers, which experience compression, and also to
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the anchors at the end of the bridge.
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In our model, we used wires for the main cables and supporting cables.
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Some of the construction is not ideal because it is difficult to simulate some of the joining
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points and anchors on a small scale.
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For this test, we need a full cast of characters.
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The Misfits versus the Bike Gang.
00:03:08
Oh, there's Crazy Guy again.
00:03:12
Classic Crazy Guy.
00:03:14
As force is applied, the cables transfer the load out to the towers and anchor points at
00:03:20
the end.
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The full force distribution maintains the integrity of the deck so that even when it does break, it doesn't really launch anyone.
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Unfortunately, I really wanted to see the crazy guy get launched.
00:03:32
This bridge supported 32 pounds, which is the same as the truss bridge.
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The truss and suspension bridges were stronger than the long beam bridge, but weaker than the arch bridge.
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This may have been unexpected, but the real advantage of truss and suspension bridges
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are that they can span longer distances than beam and arch bridges.
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Now, what we've all been waiting for.
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Crushing a Lego Man.
00:04:03
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- Idioma/s:
- Etiquetas:
- EducaMadrid
- Autor/es:
- MITK12Videos
- Subido por:
- Samuel E.
- Licencia:
- Reconocimiento - No comercial - Compartir igual
- Visualizaciones:
- 81
- Fecha:
- 30 de octubre de 2013 - 17:30
- Visibilidad:
- Público
- Centro:
- IES JOAQUIN ARAUJO
- Duración:
- 04′ 30″
- Relación de aspecto:
- 1.78:1
- Resolución:
- 640x360 píxeles
- Tamaño:
- 15.61 MBytes
