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In our last video, we looked the simple designs of beam and arch bridges.
Now let’s move into the modern age for the truss bridge
Truss bridges make use of a large frame called the truss.
That sits on top or below of the bridge deck. In this case it is on top.
All may seem like you're only adding weight to the deck
The design of the truss distributes the load through the frame so the deck does not experience as much a blowed.
Each segment of the truss experiences different loads of the tension or compression
We apply two equal loads to deck and calculate the loads in each segment which are shown as percentages of the total load.
You can see that the largest loads are on the end and top segments but the middle segments have not.
Remember that when we do the compression test spoiler alert!
Let's see if this convict can shut off this truss jail. So how do you think that truss will break?
. Discuss~ thanks for coming Yoda. I love Yoda. As you can see, the outer segments of the truss are the first to break because they were handling the largest part blowed.
The diagram showed that the outer and tough segments had the same loads.
Why didn't the top break? That's because the top pieces are lined along the grain of the wood and wood is stronger in that direction.
Adding the truss allowed the same deck planks for hold 32 pounds, which is 25 percent stronger than the beam bridge of the same length.
The final type of bridge we'll discuss is the iconic suspension bridge.
Although the only suspension bridge around us is a less than iconic but the same principles applied.
Suspension bridges utilize thick steel cables that support the deck and transfer the load to the towers into the anchors at the end of the bridge.
Supporting cables are used to suspend the bridge deck from the main cables. The main cables and supporting cables at the bridge are always under tension
The cables transfer the load to the towers which experience compression and also to the anchors at the end of the bridge. And I model.
We use wires for the main cables and supporting cables
Some of the construction is not ideal because it is difficult to simulate some of the joining points and anchors on small-scale.
For this test we need a full cast of characters. The Misfits ,verses, the bike guy and others crazy guy again classic crazy guy.
As forces applied the cables transfer the load out to the towers and anchor points of the end.
This force distribution maintains the integrity of the deck so that even when it does raise doesn't really launch at once.
.. Unfortunately I really want to see the crazy guy to crush. This bridge support 32 pounds which is the same as the truss bridge.
The truss and suspension bridges were stronger than the long beam bridge.
But weaker than the arch bridge. This may have been unexpected.
But the real advantage of truss and suspension bridges is that they can spend longer distances than beam and arch bridges.
Now what we've all been waiting for. crushing a lego man