Its no secret that counties across America are struggling with their bridges.
(Counties are typically responsible for their bridges, while the state is responsible for the primary system bridges. This leaves a huge number of bridges in county hands and in trouble.)
I am working on a concept for a single span 50′x30′ county bridge, with the goal of establishing a cheap bridge that county forces could install themselves. This is harder than you would think. Most counties have limited funds, limited equipment, and small busy workforces. (I still think a prefab bridge that is trucked to the site and quickly placed is the way to go. See my past bridge here. But a prefab bridge can easily cost twice as much as a cast-in-place bridge because of prestressing, etc)
So, while I am sitting in the computer lab proctoring a Google Sketchup test, I came up with this idea. (forgive if someone else has already done this….I think the only thing new aspect is the prestressing.)
(And this bridge is using geo-reinforced earth abutments..)
Step one – Drive the sheetpile.
Sheetpile shortens the bridge by using a high abutment system, so it easier to develop a single span bridge.
Step 2 – construct the abutments and drag or use a crane to place steel beams.
Step 3 – prestress the steel beams on site. I may need cross bracing to minimize distortion of the beams.
Step 4 – add the metal arches. The arches provide voids in the deck reducing the deadload. (I know this has been done before.)
Step 5 – place some regular reinforcement (not shown, hey I’m giving a test here!) and pour the deck. (The purple portion and the white deck are the same concrete pour. I just showed it in stages.)
So what this does is prestress the concrete deck / steel beams into a typical T-beam system. A system I think any county could build.
Step 6 – after the deck and the abutment is poured, encasing the ends of the beams, bolt on the railing. And voila, a cheap, strong county bridge. Now, give me some feedback.
Would this work?