? asked in Science & MathematicsEngineering · 1 decade ago

i need help with river bridges?

i have homework for science about what i think are called river bridges, it is a bridge over a river with a river on the bridge, the question is when the bridge was built did the builders build the bridge for the weight of the water, or the water and the boats going over it?

1 Answer

  • 1 decade ago
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    If the bridge is carrying a river over a river, the bridge dead load will be the water contained by the bridge as well as the bridge superstructure, railings, sidewalks, etc. Any boats on the river bridge do not add any vertical load to the bridge since the boats will displace the water and push up on the boats equal to the weight of the displaced water. For example, if a boat has displacement of 1000 tons of water, that means the boat while floating will push aside 1000 tons of water or 1000 tons*2000 lbs/ton * 62.4 lbs/ft^3 = 1.248E8 lbs of upward force to create the buoyancy needed to allow the ship to float. BTW, with the ships on the river bridge, the water level will rise to accommodate the displaced water volume.

    I hope this answers your question.

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