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  • General discussion about railroad operations, related facilities, maps, and other resources.
General discussion about railroad operations, related facilities, maps, and other resources.

Moderator: Robert Paniagua

 #430355  by Murjax
 
In light of the Minneapolis road bridge disaster, I have heard so much stuff on the news about road bridges not being safe because of the lack of maintenance. Well I was wondering if railroad bridges (particularly ones owned by Amtrak or other commuter rails) are under maintained like these road bridges?
 #430360  by ljeppson
 
You may recall that last summer Amtrak silver service was disrupted on the Atlantic coast for several days while a CSX bridge received emergency maintenance.

 #430367  by RichM
 
OK, I'm setting myself up to be flamed... but...

Most if not all of the bridges deemed structurally dificient or obsolete bear this designation because of design changes mandated by the DOT/FHA and various state DOT's following their construction, for things like ramp and lane widths, height clearances, steepness and visibilty associated with grading, etc.

Tens of billions are spent annually already on highway trust fund issues (that we all question, based on Amtrak's limited share of this pie.)

A catastrophe happened, but let's find out why first.

 #430375  by Gilbert B Norman
 
You won't be flamed by me, Mr. RichM; your voice of constraint and reason regarding a "delicate" matter is duly noted.

 #430389  by John_Perkowski
 
A friend of mine was a Civil Engineer, he watches engineering news as a hobby now.

Of note: The bridge in MN had a 50 year design life. It was 40 years old. It'll be interesting to read the engineering analysis of the failure.

Engineering in the slide rule era had a simple solution for variables: Over-engineer. Lots of railroad bridges fall in this category. That's one reason why railroads are harvesting abandoned line bridges (ex-MoPac, now UP Missouri river bridge at Boonville for one) for re-use.

For the Corridor, Amtrak needs to conform with standards.

For outside the Corridor, Amtrak needs to insist on due care in engineering any route it travels on!
 #430393  by 2nd trick op
 
While the incidence of rail bridge issues is relatively small, the media have not paid much attention to the simple fact that our highway infrastucture has been put under intensifying pressure due to more liberal size and weight restrictions.

When I graduated from college in 1971, the maximum length permitted for a highway semitrailer in my native Pennsylvania had just been increased from 40 to 45 feet. That figure has since been raised twice more, and now stands at 53 feet. Gross vehicle weight restrictions have been increased from 73,000 to 80,000 pounds. and the diminshed suitability of the rail network for "high and wide" moves has opened the door for much bigger loads if authorized by special permit.

Preliminary indications are that the bridge in question was not under a particularly heavy stress, but I'm still waiting for confirmation. It's worth noting that in the days of steam, some rail bridges necessitated the separation of double-headed power by the use of idler cars. And as a very heavy load crosses a truss bridge, the stresses shift to different parts of the structure. Multiply that by the chance occurrence of two or three heavily loaded 18-wheelers spaced close together and moving in the same direction -- who knows?

If any suitable response comes out of this tragedy, I would hope that our media would do a better job of informing the public how badly our transport infrastructure has deteriorated, and how much greater a cost will be occasioned by our "gotta-have-it-yesterday" attitude toward distribution.
Last edited by 2nd trick op on Fri Aug 10, 2007 2:14 pm, edited 1 time in total.

 #430394  by prr60
 
I am a civil engineer and there is no reason that a properly maintained bridge can not last 100 years or more. The Ben Franklin Bridge in Philadelphia is over 80 years old, the Delair Conrail (NJT) bridge (Philadelphia to NJ) is over 110 years old. Many Amtrak NEC structures are at or near 100 years old. Design life is related to functional use, not structural integrity.

Until we know exactly what happened with I-35W, it is hard to say what implications it will have for other bridge owners. Right now we know very little, so the implications for Amtrak are impossible to predict.
 #430396  by ljeppson
 
This suggests an analysis of what happened will require not just static modeling, but dynamic traffic modeling as well.

 #430397  by 3rdrail
 
RichM wrote:OK, I'm setting myself up to be flamed... but...

Most if not all of the bridges deemed structurally dificient or obsolete bear this designation because of design changes mandated by the DOT/FHA and various state DOT's following their construction, for things like ramp and lane widths, height clearances, steepness and visibilty associated with grading, etc.

Tens of billions are spent annually already on highway trust fund issues (that we all question, based on Amtrak's limited share of this pie.)

A catastrophe happened, but let's find out why first.
No flaming here either, Rich. Many otherwise sound bridges are given sub-par ratings, as you already noted, due to modern technical issues not relating to the bridge's solidity.
 #430400  by amtrakhogger
 
Look at Starucca Viaduct in Lanesboro Pa. built 1848, in service
and no load restrictions that I am aware of.

 #430752  by Finch
 
Well, the Thames River Bridge in Connecticut is on its way out, but it's also close to a century old. And it's a drawbridge. In its current state it certainly isn't doing so well, but at least Amtrak is replacing it. Let's hope it can limp along for just a little while longer.

 #431029  by Robert Paniagua
 
Yes, Ive been on that Thames Rivber Bridge, but even if a new bridge is built in it's place the trains can't go any faster than now, since there's a tight curve on approach to New London.

For outside the Corridor, Amtrak needs to insist on due care in engineering any route it travels on!

That would be the host railroad's responsibility, to maintain properly their bridge especially if Amtrak uses thir ROWs. Amtrak's trains are significantly faster than other trains so that's one thing there for those host railroads to keep in mind.

 #431048  by Jay Bong
 
Many parts of the Amtrak NEC date from the original PRR main line, including much of the bridges, tunnels and ROW. The 1873 B&P Tunnel in Baltimore is still in use, for example.

The bridges are safe. Despite their 90+ year age, they were designed and built for heavier loads at a different time. Being maintained and inspectly regularly, they will be fine.

The Hell Gate Bridge, on the other hand, was well overbuilt with a rigid steel arch main span to support the heaviest locomotives and loads of its time. It still is ranked as the strongest steel arch in the world. Some experts have predicted that it will be able to last over a millennium or more.

 #434727  by e.sillery
 
There is a wooden rail bridge in Tuscaloosa, AL that was completed in 1898 and is used every day by a shortline. It is about 1/2 to 3/4 miles long. It crosses the Black Warrior River and has an "S" curve in it (it was not built as a straight bridge). The trackage is leased from KCS and the bridge has more splices than I can count. There is a 10 mph restriction on it.

About 200ft. of walkway caught on fire a couple of months ago and that put the walkway out of service for a while. Even after it was replaced there is not a walkway that crosses the entire bridge. There is no walkway over the river section.

The contractor that is constantly repairing/replacing parts told me "There is no way in Hell I would ride a train across that thing."

This bridge is being maintained by a penny pinching shortline so the maintenance done is only what absolutely has to be done.