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Clearly the bridge will be pulling down on the supports so they will be exerting an upwards reaction force on their supporting pin joints. What does the direction of the reaction force tell us about the forces in the diagaonal support? What does this imply about the direction of the forces in the next strut?
Once you have understood the principles which allow you to determine the locations of tensions and compressions in the bridges you should be able to fill in a picture of tensions and compressions without the need for any numerical calculations.
More Bridge Building
Age 16 to 18
Challenge Level 
Clearly the bridge will be pulling down on the supports so they will be exerting an upwards reaction force on their supporting pin joints. What does the direction of the reaction force tell us about the forces in the diagaonal support? What does this imply about the direction of the forces in the next strut?
Once you have understood the principles which allow you to determine the locations of tensions and compressions in the bridges you should be able to fill in a picture of tensions and compressions without the need for any numerical calculations.
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