Monday, July 13, 2015

Plate Girder Movable Bridges

.pdf copy from 1915 Smoke Abatement Report, p. 489
If the caption for this photo hadn't mentioned "draw bridge," I might not have noticed that it is a swing bridge. This is the first swing bridge I have seen that is not a truss bridge.
Satellite
The satellite photo indicates that the Illinois Central now uses a set of fixed trusses. As with the truss bridges on the Cal Sag Canal, they were probably designed so that they could be converted to lift trusses. But that conversion never happened.
Bird's Eye View
Instead, the towboats are required to have pilothouses that can be lowered to go under bridges.
Bird's Eye View
I noticed while researching some Indiana Harbor Canal bridges that the abandoned Baltimore & Ohio bridge has a plate girder deck. I'm still trying to figure out how the lift mechanism for this bridge worked.

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