I was thinking today about how. Railroad bridges last so long and how regular road bridges always seem to fail or fall apart after only 50 or so years after begin built. I go under two bridges every afternoon and one has been in place for over 100 years yea it’s rusty and the concrete is starting to break but it still standing strong. But if you look at a regluar road bridge like the Hoan bridge here in milwaukee. I don’t know if you all remember about back in like 2002 or somewhere back a few years ago the bridge buckled and had to be blown up to get fixed in the part that buckled and that bridge. Is only I beleave is right around 50 or so years old. But anywho now about the other railroad bridge.I go under is only about 35 or 45 years old and that’s in better shape then. Most of the regluar road bridges. I go under everyday on my venture though this great city. But anywho now on to the question how do these bridges last so long and the other kind of bridges fall apart or desinagrate alot qiucker then the railroad bridges. But if you really think about it the railroad bridges haul alot more weight then regular ones. Do they build them stronger or what. But now if the people building road bridges would talk to the people building railroad bridges and just maybe. The bridges could last alot longer then just 40 or 50 years. Oh and the two bridges that. I go under each day one is the UP/CNW bridge on. South 6th St. and the other one is also ON south 6th St that runs over 6th and morgan Ave. Oh well that’s bout it hope to be hearin from you all soon
…I would imagine the duty cycle {work it has to do}, is programed into the build to last “X” amount of years, and I suppose railroads do build their structures to do the work for a longer life span than highway engineering does for their bridges. Why…I really don’t know, but maybe cost.
Maybe because our trains are driven by well trained and well paid professionals and a large percentage of cars are driven by homicidal maniacs and drooling idiots.
Railroad bridges are designed and built to a significantly different set of standards that hiway bridges. Not too many 400,000 pound trucks on the road but many of the locomotives weigh that much.
Second reason in northern climates or near the ocean is salt - any small crack in the concrete on a hiway brdige and salt will eventually work its way into the core of the structural members and start rusting the reinforcing bars. Since rust takes up more space than clean steel, the rusting process also starts putting pressure on the bridge from the inside - where it will eventually push chunks out of the concrete and weakening the bridge. That is why the steel in new bridges is covered with green epoxy. Rarely do railroads use salt on their bridges so internal corrosion is much less of a problem.
dd
…We have a pair {end to end}, through truss RR bridges here in Muncie that have been out of service {hence, no maintenance}, since around 1970…They still look like they would stand another 75 years or so if the concrete / stone pier holding up the center where they meet in mid river will stay sound.
I suggest Interstate highway bridges are simply not built in a manner that allows them to last that long under their work loading. RR bridges are, or were built of heavy structural steel in the past because of heavy loading of large steam engines and simply last longer. I wish Interstate bridges {in general}, were able to last that long too. Driving over them and knowing the heavy trucks have been pounding them {in some cases}, for almost 50 years and it makes me wonder passing over them how well they have been inspected recently.
The old Erie bridge in Hancock, NY is still going strong, albeit under minimal traffic. The highway next to it is on it’s third bridge…
It is all about the salt…
Another factor, though, is that modern engineering is capable of designing a structure that will do the job, and not a lot more. Back in the day, many structures were over-engineered. They were built with a margin of significant error.
Ive seen entire Interstates AND Bridges replaced twice or three times in the same areas over the two decades or so.
What a waste.
Build them BIG, strong and Smooth. Do it right the first time cost be damned. They will outlast your children’s children.
Well, I would guess that railroad bridges are better because they have a corporation interested in its survival. Road bridges are owned and maintained by government, who does not depend on the bridge for profit returns.
[#ditto]
When that runaway river boat and barge knocked down the I40 bridge in Oklahoma, you BETCHA Uncle Sam fell out of bed reaching for his wallet. They replaced it under-schedule within 60 days flat.
Or maybe back in the early 90’s that Interstate 70 Ramp was eaten by a massive hole or some sort coal mine (Never did find out the rumor/fact mess) that required a 20 mile roundabout detour that eats an hour or more out of a regular driving day up there in the midwest. They toiled night and day to replace that lost ramp ASAP.
Look at the one bridge they built way down south along the Rio Grande. A nice fat 6 Laner with all the best. Problem was it sat empty while everyone continued to flood the already over-worked, choked Laredo area 50 miles away.
Road projects languish for months and YEARS in the same OLD places. Governments at all levels get re-elected every 4 years and the new people have to re-invent the wheel all over again. Hell, some of Germany’s Autobahns were built in Hitler’s time and sections still in use today at frigging 200 MPH!
If I gotta say ONE positive thing about this whole interstate business is that Arkansas FINALLY slapped a few feet of fill, blacktop on what was truck breaking concrete, and I thought PA had the worst, especially between Frystown and down towards the Maryland Line. They fixed that too. AND the bridges across the entire PA turnpike, those bridges served out thier useful lives and were replaced pretty promptly. OORAH!
Ohio make thier turnpike 3 lanes wide and banned toll paying trucks from using that far left. Oh well. Back to US 20 we go!
Dont get me started all over again.[soapbox]
That is exactly it.
I saw a Nova special on bridges several years ago that covered this topic somewhat, and I just found the transcript. They also spoke about old bridges being very “over-designed” to the point you could remove bolts, etc. and the bridge will remain just as strong. Apparently with designing highway bridges today as a means of government cost-cutting the real challenge is to design a bridge that will just barley hold a specified weight. Of course, such structures never last long because they aren’t really designed to. Sad, really. So short-sighted. That’s government for ya.
Thank you deepspire for the link. I too watched this show. The statement about making a bridge barely strong enough was unsettling. I add, it is a very beautiful bridge.
Older bridges, including railroad, highway, aqueducts, etc. were often over-engineered and over-designed because engineers of the time had few ways of accurately measuring the stresses that would be applied to the spans and were consequently dependent on educated guesses and prior experience, which would include bridge failures. The original design of the Quebec Bridge failed while still under construction. We only see the successes, not the failures.
Two factors have been brought up regarding the relatively short lifespan of post-war highway bridges: salt and cost. Both are valid, especially since I don’t see anybody volunteering to pay higher gasoline and other taxes to cover the added expense of building an over-engineered bridge that will still be subject to the depredations caused by the use of salt and other chemical de-icers.
Speaking of sturdy old bridges…
Does anyone out there know where I could obtain drawings & info on the Hanging Bridge in the Royal Gorge, Colo. ? I hope to reproduce this bridge as accurately as possible in a highlighted portion of my next layout. thanks in advance for your help.
It hasn’t been a hanging bridge for more than 50 years! [(-D]…Inspected it in 1998 and 2000.
(Don’t tell the touristas on Lindsay Ashby’s toy train![;)]
UP has the only complete set of plans for the bridge. Go visit CRRM in Golden and go look at the D&RG bridge records and the ICC field notes from 1918.
[bow][bow][bow]
E50 to E80 certainly trumps E10 to E30
Boy. The locals sure had me fooled.
…I agree…Overbuild on material and design probably is the most accurate answer of the longer lasting RR bridges as compared to newer Interstate structures. Newer Interstate structures are designed just to the need and almost no extra, hence not much longevity built in.
I’d say the same applies with buildings. Empire State Building as an example…Way overbuilt with steel and design according to many articles I have read on that subject.
Most railroad bridges were designed and built during the age of steam. Steam engines due to the counterweights that were used to balance the drivers and the power stroke applied to the drivers created a tremendous pounding action upon the rail and all the struructres that steam engines operated. The higher the speed, the more severe the pounding. As a consequence rail bridges designed and built during this era built to withstand this pounding and built heavily enough to withstand the pounding with minimal continual maintenance. Were the engineers and bean counters of the 21st Century to view the designs of these structures they would conclude that they were vastly overbuilt and much too expensive to construct. Today’s diesel electric powered trains don’t develop anywhere near the stresses up on the track and bridge structures that the steam engines did, however the longer and heavier cars that today’s carriers handler are more stressful upon the track structures than were the cars of yesteryear.
I love pics and the history of Rockville bridge. This is great example of overbuild that will last through the ages. Unfortunately, my pics were unsatisfactory. I like this one by Carl Weber
http://rrpicturearchives.net/showPicture.aspx?id=358952