"Ballasted Deck" bridge question.

Matt,

Interesting reading, especially the part about keeping bridge track level with grade track.

 

http://www.arema.org/publicati...Guide/PGChapter8.pdf

 Wow that is an interesting question

 

 I really never gave it much thought,but on the east side of Williamson,WV they replaced two open steel bridges on the main line with two concrete structures.And yes they are ballasted just like the main that lays on the ground.I believe the NS did the same thing when they created a 3rd main going into Cincinnati Ohio ,having built several miles of concrete "viaduct" .

With regard to the linked article's comment concerning the difficulty in maintaining same grade approaches and exits from open deck bridges; about 20 years ago, I was in the cab of a CSX B36-7 on the head end of an office car train.  We were just north of Mobile on the line to Montgomery and the RFE had us running at the maximum permissible track speed of 79 MPH.  I remember coming off the end of one open deck bridge and it seemed like the engine went airborn for a second or two.  I recollect the "landing" as being bone jarring, it was that hard.

 

Curt

That was a good article and the site is a good source of basic information. If you're really "hard core" they sell the actual manuals.

 OUCH! Lucky you guys stayed on the rails.

Matt

 

Great subject!  And thanks to Lima for posting the AREMA link.

 

There are some subtle variations that can be interesting to model.  On the Milwaukee Pacific extension all those high trestles had ballasted decks.  But in the Washington Cascades they were concrete while in the drier areas to the east they were timber.  Here is a look at the model of the Eagle Nest trestle on the NWTL.

 

 

 

The GN typically used an open deck on their truss bridges as on this model of the bridge leading into Sky.

 

 

The GN truss bridge over the North Fork of the Skykomish River at Index has a ballasted deck for the same reason as many of the Milwaukee's trestles.  The ballasted deck makes it possible to maintain a continuous curve and superelevation across the bridge and avoid a speed restriction.

 

 

Ah, yes, the beloved FB-2 "no springs" truck -- I think all CSX B36's had em....

Best, SZ

I understand ballasted decks are highly desired on any line running passenger trains and high speed freight. Others have sited the reason...much smoother running and alignments.

 

Neil

I can't speak for any other railroad, but Santa Fe went on the rampage to put ballast decks on all main track bridges on the transcontinental main line and the main routes into Texas.  By the 1980's, there were only a few open deck bridges remaining.  We had two very small open deck bridges on the Needles District, near Saltus, and they both rode well at 90 MPH, but they also got a lot more maintenance than the other bridges did.  They received ballast decks around 1990.

Great Information everyone... Certainly does make a lot of sense to have the ballast.  Great question Matt.
Chris

I thought most (all?) freight diesels maxed out at 70?

 

---PCJ

No.  It depends on the load and the gear ratio.  

20 of the Santa Fe F45's, 10 SD45's, 10 U33C's, and some of the SD45-2's were geared for 90 MPH for use on the 79 MPH Super C freight train (and, in the case of the F45's, 90 MPH passenger service when needed).

 

Back to the bridges . . .

Thanks for the information.  I was debating whether to ballast several decks on my layout but this thread has swung me in favor of doing it.

 

Poppyl