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Old 05-13-2020, 09:42 PM   #2
jac_murphy
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Join Date: Sep 2011
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Both ballast- and open-deck bridges are common. The trend is moving more and more towards ballast-deck bridges since it's easier to control thermal expansion, they can be surfaced using regular equipment (and are less prone to developing surface deviations at either end where the roadbed meets the bridge,) there's less special hardware (hook bolts, spacers, bridge timbers, etc) involved, and there's reduced wear on the structure itself since the ballast tempers the vibration somewhat (which also makes for a bit of a smoother ride.)

In the photo you linked, I'll bet that bridge started its life as an open-deck bridge and was later retrofitted with a ballast deck.

-Jacques
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