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This crane has a 3ft boom and 2 windlasses (to control the boom and the load). Also, there are outriggers at each corner to keep the crane level.

 

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I used the windlass to raise the boom to  75 degrees. 

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Tower cranes need counter-weights to keep from tipping over- that's what the red brick is for. 

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decktruss.jpg


This is a deck truss- the load (cars, people etc.) pass on top of  the truss. I used single wide beams, connected at the joints with

8-32 machine screws. The bottom middle member is a string tensioned with a turn-buckle.

 

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The live load is approx. 100lbs. This puts tension on the line (string) on the bottom. I'll use the Method of Sections to compute the amount of tension on the string.

 

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In a through truss, the live load passes through the truss. I only put around 50 lbs. on the deck.

 

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In this lift bridge, the line is attached to the end of the deck, then goes over a sheave (pulley) high up on the tower, and then down to the windlass.

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Here the line  goes over a pulley mounted lower down on the tower. The lower angle means that it will take more force to raise the deck of the bridge.

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cablestayed.jpg

In a cable-stayed bridge, the deck is supported by cables (string in this case) that go in straight lines from the towers to the deck.The main span (the distance between the 2 towers) is almost 6ft.

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Suspension bridges differ from cable-stayed bridges.   The 2 main cables rest on top of the towers,  curve down between the towers and then attach to the anchorages. The deck is held up by the "suspenders" the short black lines that hang down from the main cables and connect to the deck.

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