Deggesty Ed, certainly, proper maintenance is not a temporary patch job. It is my understanding that MC was referring to need for a replacement, not simply a patch job.
Ed, certainly, proper maintenance is not a temporary patch job. It is my understanding that MC was referring to need for a replacement, not simply a patch job.
He was. He believes the bridge is a complete lost cause. I am trying to find out whether that is true or not. I am curious. I have seen nothing that explains that it IS such a lost cause.
So, there's a 1.3 BILLION project proposed. I am curious.
On the plus side, the 1.3 BILLION bridge won't need much maintenance, being concrete and immovable and all. So Amtrak's inability to do that sort of thing won't be a problem anymore.
Ed
wanswheel Excerpt from FRA scoping document, Dec. 2006 https://www.fra.dot.gov/eLib/Details/L01424 In addition to the age of the Portal Bridge, several aspects of the bridge's design are problematic. The bridge consists of seven spans and totals 961 feet in length. The middle span is a 300 foot long moveable swing span and is able to pivot to an open position (perpendicular to the rail line) to allow marine traffic to pass through the bridge. When the swing span is open, the bridge is closed to rail traffic. Special rail connections, known as “miter rails,” allow the rails to disengage and the bridge to open and close. These connections are mechanically separated and automatically controlled for the swing span to open and then are realigned after it is closed. Mechanical wedges must lock the structure in the closed position and with electric traction special mechanical catenery connections must join continuous contact wire on either end of the bridge. Depending on the reliability of this process, the period of time the bridge is closed to train traffic may be adversely affected resulting in train delays. Due to these issues, older swing span bridges are now being replaced by other types of moveable bridges such as vertical lift and single-span bascule bridges. The miter rail connections have been an ongoing problem since the Portal Bridge was constructed, and the connections have been replaced several times. They are vulnerable to maladjustment and negatively affected by temperature changes. The rate of wear on these miter rail connections is worsened with higher train speeds and frequencies. As a result, while trains can operate at 90 miles per hour (mph) on adjacent portions of the NEC, speeds on the Portal Bridge were previously restricted to 70 mph, and most recently (December 2006) have been permanently restricted to 60 mph.
I started reading the cited document and got several pages in. I noted the statement twice claiming the bridge was opened "frequently". Turns out "frequently" means about every four days. And 70 of those are for some sludge barge. Right.
That makes me suspect other claims in the document. Consider the miter rail connections. Which need frequent attention. And yet, 100 years later, modern technology can't come up with an improvement on the design. Right.
7j43k mudchicken http://www.northeastallianceforrail.org/2011/08/a-21st-century-nec-the-top-four-failing-bridges-on-the-nec.html With the number of cycles that bridge has gone through, I'm amazed it's still there. Movable bridges aren't "off the shelf" rascals and fatigue is a major issue in older movable bridges. Even overdesign can get you only so far, happy circumstance that it might be. You can only "band-aid" to a point and then the slow orders and loading reductions of a bridge at or beyond capacity are a nighmare with diminishing returns. (Since a 1996 accident/derailment and an earlier fire, the thing is restricted to 60 MPH when it used to be 90MPH.) I wish you could see some of the AREMA presentations on this rascal and some of its cousins. This bridge would cost more to restore than to replace. There are foundation issues and bent+pier issues in the waterway that also are in play. PDN will comment eventually. I don't understand the logic & reason of the folks who think a steel bridge, especially a movable one, can last forever. bubblegum, band-aids, belts and supenders? - no thanks. I read the section on the Portal Bridge in the cited document. I saw evidence of incompetent maintenance. But I saw nothing noted concerning failure due to age of structure. And I don't think doing proper maintenance is "bubblegum, band-aids, belts and supenders". Ed
mudchicken http://www.northeastallianceforrail.org/2011/08/a-21st-century-nec-the-top-four-failing-bridges-on-the-nec.html With the number of cycles that bridge has gone through, I'm amazed it's still there. Movable bridges aren't "off the shelf" rascals and fatigue is a major issue in older movable bridges. Even overdesign can get you only so far, happy circumstance that it might be. You can only "band-aid" to a point and then the slow orders and loading reductions of a bridge at or beyond capacity are a nighmare with diminishing returns. (Since a 1996 accident/derailment and an earlier fire, the thing is restricted to 60 MPH when it used to be 90MPH.) I wish you could see some of the AREMA presentations on this rascal and some of its cousins. This bridge would cost more to restore than to replace. There are foundation issues and bent+pier issues in the waterway that also are in play. PDN will comment eventually. I don't understand the logic & reason of the folks who think a steel bridge, especially a movable one, can last forever. bubblegum, band-aids, belts and supenders? - no thanks.
http://www.northeastallianceforrail.org/2011/08/a-21st-century-nec-the-top-four-failing-bridges-on-the-nec.html
With the number of cycles that bridge has gone through, I'm amazed it's still there. Movable bridges aren't "off the shelf" rascals and fatigue is a major issue in older movable bridges. Even overdesign can get you only so far, happy circumstance that it might be. You can only "band-aid" to a point and then the slow orders and loading reductions of a bridge at or beyond capacity are a nighmare with diminishing returns. (Since a 1996 accident/derailment and an earlier fire, the thing is restricted to 60 MPH when it used to be 90MPH.) I wish you could see some of the AREMA presentations on this rascal and some of its cousins. This bridge would cost more to restore than to replace. There are foundation issues and bent+pier issues in the waterway that also are in play. PDN will comment eventually.
I don't understand the logic & reason of the folks who think a steel bridge, especially a movable one, can last forever.
bubblegum, band-aids, belts and supenders? - no thanks.
I read the section on the Portal Bridge in the cited document. I saw evidence of incompetent maintenance. But I saw nothing noted concerning failure due to age of structure.
And I don't think doing proper maintenance is "bubblegum, band-aids, belts and supenders".
Johnny
BaltACD Anybody ever been stopped on a 'substansial' bridge and traffic is moving on another lane of the bridge? Ever noticed the bounce and sway you feel as that lane of traffic moves, especially when trucks pass your location. All that movement generates the repetitive stresses that all the elements of the bridge are faced with - over and over and over - cycle after cycle. Put the elements of a bridge under these repetitive stresses for 100+ years and the elements of the bridge are stress worn out, no matter how overbuilt the structure may have been at its creation. A structure built today to replace one of these 100+ year old bridges most likely won't have a lifespan anywhere near 100 years. Modern engineering calculates the stresses too prcisely and design their structures to cover only the known stresses plus an additional margin for 'safety' (however, that margin most likely will be less than the 'old timers' rule of thumb guesses would be).
Anybody ever been stopped on a 'substansial' bridge and traffic is moving on another lane of the bridge? Ever noticed the bounce and sway you feel as that lane of traffic moves, especially when trucks pass your location.
All that movement generates the repetitive stresses that all the elements of the bridge are faced with - over and over and over - cycle after cycle. Put the elements of a bridge under these repetitive stresses for 100+ years and the elements of the bridge are stress worn out, no matter how overbuilt the structure may have been at its creation.
A structure built today to replace one of these 100+ year old bridges most likely won't have a lifespan anywhere near 100 years. Modern engineering calculates the stresses too prcisely and design their structures to cover only the known stresses plus an additional margin for 'safety' (however, that margin most likely will be less than the 'old timers' rule of thumb guesses would be).
I do not see that a bridge bouncing and moving must necessarily lead toward fatigue failure. It would seem that if the flexing stays within elastic limits, the bridge can bend pretty much forever.
Or do elastic limits change over time? It was my impression from an Engineering Materials class that they did not.
Quoting MC: "bubblegum, band-aids, belts and supenders? - no thanks"
You reminded me of a description of home-rolled cigarettes which was, I believe in the Saturday Evening Post late in WWII. The two I especially remember were "the Drooper--too little and too late," and "the Blooper--held together with gummed tape." The Portal Bridge certainly would not be described as a "drooper," for it has done well over the years. However, no one should even consider patching it up, but plans should be made soon so that it will "so round, so firm, so fully packed"--and not a draw-- that it will do its job for another hundred years at least.
Never too old to have a happy childhood!
cx500 7j43k: "Replacing rivets" is not the issue.
7j43k:
"Replacing rivets" is not the issue.
Darn. 'Cause I thought I could sell my method to Amtrak and make a big profit. Double darn.
They are simply what fasten the various structural members together and it is no doubt those structural members that are starting to show their age. With older bridges, especially those with frequent traffic, fatigue becomes a concern. I don't know what type of bridge it is, but am assuming it is a through truss, with floor beams and stringers supporting timber ties. Those members can be renewed but that is a major project in itself since the track panels they support must be removed. No track equals no trains on that track, a huge bottleneck. Fortunately railroads designed their bridges very conservatively which is why many are still serving years after contemporary highway bridges were replaced. If the main trusses are showing signs of age, replacement of the entire truss, and hence the bridge, is the only real option. Moveable spans, whether lift, bascule or swing spans, are a continuing maintenance headache. Obviously with old mechanisms the problem is more acute but even mdern machinery is never problem free. It is not just the main mechanism; there are also locking pins and movable rail joints, all of which must be kept in precise adjustment and tied into signal circuits. A new higher bridge crossing that eliminates the need for a movable span will have enormous long term benefit. I presume any new bridge would also have a ballasted deck, also preferable for track maintenance and ride.
Fortunately railroads designed their bridges very conservatively which is why many are still serving years after contemporary highway bridges were replaced. If the main trusses are showing signs of age, replacement of the entire truss, and hence the bridge, is the only real option.
Moveable spans, whether lift, bascule or swing spans, are a continuing maintenance headache. Obviously with old mechanisms the problem is more acute but even mdern machinery is never problem free. It is not just the main mechanism; there are also locking pins and movable rail joints, all of which must be kept in precise adjustment and tied into signal circuits.
A new higher bridge crossing that eliminates the need for a movable span will have enormous long term benefit. I presume any new bridge would also have a ballasted deck, also preferable for track maintenance and ride.
I can see that a bridge that was not designed well could have fatigue failure problems. Which would be why a bridge would take some time to fail (famous highway bridge failure in Minneapolis several years ago), as opposed to collapsing under the first loading (NP bridge of river a long time ago).
But, so far, all I've heard is "It's old!", as if that's a reason to replace the bridge. It is not. BNSF, for example, is still using bridges along the Columbia River that were installed when SP&S was first built--about 100 years ago. I have also seen mention of the locking pins and movable rail joints, but never a real discussion about why, exactly, they can't be repaired. If needed.
I find it odd that obtaining an accurate description of the failings of the bridge is difficult/impossible. If there was an inspection/evaluation conducted, where is it?
I found this interesting discussion of fatigue failure online:
http://www.nordicsteel2009.se/pdf/147.pdf
Falcon48 Of course, this has nothing to do with the main thrust of this thread. But someone may find it interesting (then again, maybe not).
I found it interesting. Thank you.
"Replacing rivets" is not the issue. They are simply what fasten the various structural members together and it is no doubt those structural members that are starting to show their age. With older bridges, especially those with frequent traffic, fatigue becomes a concern. I don't know what type of bridge it is, but am assuming it is a through truss, with floor beams and stringers supporting timber ties. Those members can be renewed but that is a major project in itself since the track panels they support must be removed. No track equals no trains on that track, a huge bottleneck.
Wizlish * * * 2) Law is that any maritime traffic that wants the bridge open has the right of way (navigation came before the railroads). You might change that with legislation, but IIRC it's a can of worms with extended implications. * * *
* * *
2) Law is that any maritime traffic that wants the bridge open has the right of way (navigation came before the railroads). You might change that with legislation, but IIRC it's a can of worms with extended implications.
A relatively trivial point about "drawbridge law".
Drawbridges over navigable waterways are governed by U.S. Coast Guard regulations (49 CFR Part 117). The "law" that vessels have the right of way is the general rule under the Coast Guard rules, but CG can make exceptions without a change in legislation. There are, in fact, pages and pages of exceptions and special operating procedures for specific drawbridges in Part 117, Subpart B. Among these are special operating procedures for the Portal Bridge in 49 CFR sec 117.723, as follows:
Wizlish A couple of quick answers: 1) No, adding another track to the existing structure would be structurally difficult if not impossible -- probably cheaper to install a whole new parallel bridge. In my opinion, cheaper to replace with a slightly higher fixed structure designed and built to carry the necessary number of parallel tracks...
A couple of quick answers:
1) No, adding another track to the existing structure would be structurally difficult if not impossible -- probably cheaper to install a whole new parallel bridge. In my opinion, cheaper to replace with a slightly higher fixed structure designed and built to carry the necessary number of parallel tracks...
So a third or fourth track is DESIRED. But then, is it needed? There are choke points on most any railroad (and freeway, as I've found out). Railroads design around that. Until they can't. There had better be some sort of study on this matter demonstrating the need for more tracks.
I can see that. There could be many and varied incentives to have some or all of the "customers" adapt to restricted access.
I have little hesitation in saying that a fleet of special low-clearance tugs or whatever would cost far more than any bridge replacement, even if nothing else were to be improved with the bridge structure and approaches.
Only need one. And, as to cost, see above.
3) Cracking, corrosion, problems under riveted joints. Look at some of the discussions involving the New Haven shore line bridges, of similar vintage and general design quality.
Depending on the extent of the damage, my very rough estimate for replacing all the rivets is 8 million. And the new bridge(s) are how much?
4) It did not help that a considerable period of time with deferred maintenance elapsed, and I suspect that maintenance under Amtrak ownership is not everything it should be. Steel bridges require continuous maintenance and reasonably prompt attention when problems start. Portal and other opening spans further south on the NEC have been the subject of other discussions here. (You can search for them with the 'search conversations' tool on the Classic Trains site...)
I did a search for Portal Bridge before posting and didn't find anything. I didn't read all of them, mostly just looked at the subject line. Beyond that, I'm not sure what the search term(s) would be.
On deferred maintenance, I had a feeling that might be so. Would I be correct in assuming that Amtrak continually kept Congress and the Executive apprised of this? Sort of: "We did our part. We TOLD you this would happen years ago, and you ignored it." Alternately, perhaps they didn't, as there could have been stress generated by an even larger bill to run Amtrak.
Low-clearance tugs are not that big a deal on the Illinois Waterway. I've seen any number of towboats equipped with a wheelhouse that can be lowered while in motion to fit under any number of bridges.
Wizlish There are a couple of major issues: it's track-capacity limited,
There are a couple of major issues: it's track-capacity limited,
Meaning a third track can't be added?
and it is so low that it has to be made 'openable'.
I believe there's 75 loads of sludge in a barge, plus 15 "others". Since the sludge is not time-sensitive, the movement of those 75 loads could happen when the tracks are clear. Unless, of course, the tracks are, or would be, busy 24 hours a day. Even then, I do wonder if the barge itself couldn't easily fit under the closed bridge. And a special low-clearance tug would likely be cheaper than a new bridge. And also useful in other service.
Much of the structure dates back to the NYCR construction era, IIRC, which makes it old in the tooth in ways that are not easy to detect with NDT methods that work on in situ structures.
So there are likely undetectable flaws. I am curious what they might be. Since, although they are undetectable, they are apparently predictable.
The replacement is 'just' higher enough that it doesn't have to be openable. The designs I've seen have the bridge made in reinforced concrete, which solves most of the long-term corrosive issues in a marine environment.
There are a LOT of steel bridges in salt water environments. I suppose there must be some research on long-term durability.
There are a couple of major issues: it's track-capacity limited, and it is so low that it has to be made 'openable'. Much of the structure dates back to the NYCR construction era, IIRC, which makes it old in the tooth in ways that are not easy to detect with NDT methods that work on in situ structures.
The replacement is 'just' higher enough that it doesn't have to be openable. The designs I've seen have the bridge made in reinforced concrete, which solves most of the long-term corrosive issues in a marine environment. I do not know whether the 'final' design will incorporate access from the adjacent commuter trackage (ex-EL, isn't it?) which would increase some of the convenience for 'one-seat' service to NYP from some interesting points.
Portal Bridge is in the news, again. New York Times, today.
It's just GOTTA be replaced. At no small expense.
And yet, I never hear any real info about what's wrong with it. Except that it's old.
Does anyone out there have information about what's wrong with the bridge?
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