Does anyone know the standard width between girders on ballasted deck plate girder bridges? I know that if the bridge is on a curve the bridge is wider to account for inside and outside curve overhang of long cars. But what is the width when the bridge is on tangent track and has tangent on both ends with no curve overhang to deal with?
Actually, what you are asking about are ballasted through plate girder bridges. A deck plate girder bridge, whether ballasted or open timbers, has the girders below the rails and there is no clearance issue.
Returning to your question, I believe it may vary depending on the state, since different states have slightly different clearance requirements. But in general I think you will be looking at 8’-0 to 8’-6" from centerline of the track to the inside edge of the top flange of the girder. If the top of the girder is less than 4 feet above top of rail, in some jurisdictions the distance can be reduced.
John
Totally dependent on the individual state rules and how that applies to the knees (butress braces) as connected to the floor beams connected to the plate girder on either side…
New construction or grandfathered in? (what standard?)
Either standard. Doesn’t matter.
In the real world, it DOES matter.
Most states, current standard, would be 17 feet between closest faces. (Look at AREMA CH. 28 for the state clearance reg that applies)…
For tangent track the normal spacing for center to center of girders on a through girder is 20 feet.
Don’t forget the width of the top flange of the girder - usually half on each side - needs to be added to the minimum horizontal clearance dimension to get the closest possible girder spacing. The top flange width can vary depending on the length of the span - anything from 12" to 24" +/- so there could be a little variation there. If I were a designer, I’d go with the 20’ as suggested above - and would consider maybe even 22 - 24’ to allow for wide load moves and other unusual needs, albeit at the price of a more expensive floor system.
- Paul North.
If it’s anywhere near a switch, you wind up adding another 36"-72" for walkways for the ground monkeys…but the kicker is still what railroad in what state.???
You do not just order one of those rascals out of a book, you design to suit the situation, railroad preference (esp regarding new construction, all are slightly different in approach) and the applicable regulations.
Open deck or ballast deck?