blue streak 1The report was only factual since it was a FRA and not NTSB report.
Thanks to Chris / CopCarSS for my avatar.
blue streak 1 According to the accident report UP originated the train (where ?).
Johnny
Two more reports of boats on rivers damaging or destroying railroad bridges:
In 1978, I was taking the Floridian from Birmingham to Chicago, and while I was waiting for the train, we were told that a tow had hit the Southern bridge across the Tennessee at Decatur, Ala. Rather than wait for a full assessment of the damage and perhaps necessary repair, Amtrak chartered buses to ferry passengers between Birmingham and Nashville. I do not recall hearing, later, of necessary repair.
One of the roads that was absorbed into the East Tennessee Virginia and Georgia was built from Rome, Ga, and Meridian, Miss., by way of Anniston, Selma, Demopolis, and York, Ala. I do not remember just what year it was that a riverboat hit the bridge across the Tombigbee at Demopolis (I do not have the memory of resident of Benevola, Ala. who told me this), but the 6/15/31 timetable of the Southern shows a through train between Rome and Meridian (using the AGS between York and Meridian), and the next timetable I have (9/36) shows no service between Demopolis and McDowell (4.9 miles west of Demopolis). The Southern did not rebuild the bridge, but used the line from Marion Junction to Akron to handle traffic to York from Selma. Even this line, as well as the line from McDowell to York, is gone now.
There is a note to the Rome-York timetable--"Note: No train service betweenDemoplis and McDowell, Ala. Through passengers between Selma and Meridain handled between Marion Junction and Akron. See Tables 66 and 10. A passenger would really have to want to go from Selma to Meridian, since he had to take a mixed train at 5:00 am, and would wait in Akron from 8:40 until 10:40 for the Queen and Crescent to take him on to York and Meridian. Eastbound, he would leave Meridian on the local, #18, at 6:30 am, arrive in Akron at 8:43 am, leave on the mixed at 9:30, and arrive in Selma at 1:05 pm.
Deggestyblue streak 1 According to the accident report UP originated the train (where ?). The rocket motors are made in Utah, near Salt Lake City.
The rocket motors are made in Utah, near Salt Lake City.
The Shuttle SRM's are made in Alliant Techsystem's plant in Promontory.
- Erik
Question :: What is the route of the SRMs? UP - KCS - M&B - CSX - FEC? Could be the gulf coast route of CSX (L&N) could not take the overweight cars?
nanaimo73 I can think of two bridge failures here in British Columbia, both were wooden bridges owned by Canadian National. A bridge collapsed under a freight train, which resulted in the death of two CN employees on May 14, 2003 near McBride, British Columbia.http://www.tc.gc.ca/eng/mediaroom/releases-nat-2004-04-h031e-3527.htm The other was on the line to Kitimat. It happened as the wood towers were being replaced with steel, and a crane was on the bridge at the time.
I can think of two bridge failures here in British Columbia, both were wooden bridges owned by Canadian National. A bridge collapsed under a freight train, which resulted in the death of two CN employees on May 14, 2003 near McBride, British Columbia.http://www.tc.gc.ca/eng/mediaroom/releases-nat-2004-04-h031e-3527.htm
The other was on the line to Kitimat. It happened as the wood towers were being replaced with steel, and a crane was on the bridge at the time.
Timber structures are still driven by railroads in places. (For that matter, there are still timber trestles/bridges still under US Highways and State Highways here in Colorado.) There are ways to stiffen bridges as well (eg steel caps and stringers or T-Rail under the ballast decks)....Shortlines probably more than Class 1's, but the thinking that goes behind the decision(s) makes it interesting, usually centered around lifecycle economics, climate and tonnage.
Murphy Siding blue streak 1The report was only factual since it was a FRA and not NTSB report. ? Can you explain that comment?
? Can you explain that comment?
Personal observation....NTSB findings seem to be swayed more by political winds from time to time.
Never too old to have a happy childhood!
mudchickenTimber structures are still driven by railroads in places.
Timber structures are still driven by railroads in places.
I'm guessing that a timber bridge can be put in place faster than most steel or concrete bridges as a pile driver can drive a lot of piles in the time it takes to prepare foundations for a steel or concrete bridge. If conditions are such that a timber bridge will last more than 30 years, it wouldn't take much of an initial costs savings for it to be cheaper in the long run to replace the bridge when needed.
A recent "Seconds from Disaster" about the Bayou Canot accident asserted that the investigators determined that the bump from the barge should not have damaged the bridge, and in fact part of the bridge that was contacted (the non-swing part) did not move. The problem was that the bridge was a swing bridge whose swing mechanism was "decomissioned" improperly.
Unfortunately, only the *rails* were holding the bridge in place. When the barge struck the bridge part of it hit the swing span and the rails deformed enough to allow the bridge to move several inches.
Had the swing span been fastened in place the accident would not have happened. The barge impact would have had little to no effect.
Of course the barge should not have been in the canot, but the bridge should have been fastened correctly.
It is not just one factor in this case.
The full report by the TSB of Canada on this McBride bridge collapse - consisting of 69 pages, approx. 654 KB in size -
RAILWAY INVESTIGATION REPORT - R03V0083
MAIN-TRACK DERAILMENT - CANADIAN NATIONAL TRAIN NO. 356-51-14
MILE 7.9, FRASER SUBDIVISION - MCBRIDE, BRITISH COLUMBIA
14 MAY 2003
- can be found at -
http://www.tsb.gc.ca/eng/rapports-reports/rail/2003/r03v0083/r03v0083.pdf
Short version from page 41 (49 of 69 of the 'PDF' format version) is that there were severe deterioration in some of the timber trestle components - which had been identified 4 years earlier - but which were later overlooked and not followed-up on:
2. It is most likely that cap 15 crushed under the weight of the lead locomotive when its bearing capacity was exceeded, leading to the bridge caving in and the subsequent derailment.
3. As the load shared by stringers 5 and 6 of span 15 was increased due to the internal rot of the adjacent stringers, the reaction load transferred to cap 15 was concentrated over a smaller area, thus exerting increased stresses over the existing void in cap 15.
4. The condition of cap 15, identified as reject in the 1999 detailed report, was not reflected in subsequent inspection reports. Therefore, its continuing deterioration was not reassessed.
5. The failure to identify the urgency and the severity of the condition of the bridge was not recognized, despite subsequent inspections, because of shortcomings in the inspection, assessment, planning, and maintenance process.
6. As a result of heavy workload, and overlapping duties during job transitions, the Planning and Inspection (P & I) Engineer relied on the inspectors’ overall assessments and most recent visual inspection reports, which did not indicate any deficiencies on the bridge. Therefore, the severity and urgency of the condition that was identified in 1999 was not recognized.
- Paul North.
HAd a trestle collapse under a loco in 2008 in Columbus Jct Iowa. Also Turkey River bridge ( not sure if it was 2008 still or earlier for this one) up on the Marquette sub. Two bridges one railroad. Kinda rare these days.
Yes we are on time but this is yesterdays train
CShaveRR I remember one near failure of a bridge here in Chicago. It was the CTA's connecting line between the old south side "L" to the new line in the median of the Dan Ryan Expressway. Somebody riding under this bridge on a commuter train noticed what he thought was a crack in one of the girders--and he was right. Things were very hastily shored up, and the line was returned to service in a relatively short time. I don't know to what extent the bridge was rebuilt, but it is now used by the CTA's Orange Line trains to Midway Airport.
From the Transportation Research Board's publication "EVALUATION AND FIELD TESTING OF THE DAN RYAN RAPID TRANSIT STRUCTURE" at - http://pubsindex.trb.org/view.aspx?id=210102 [emphasis added - PDN] -
"The Dan Ryan rapid transit structure is a 40-span, 4,000-ft-long elevated structure that carries Chicago Transit Authority (CTA) rapid transit trains into and out of the Chicago Loop. The structure, which was completed in 1969, consists of welded stringers and is supported by steel box-girder bents. Splices in the stringers are field bolted. The steel stringers carry two sets of track on a ballasted concrete deck. In January 1978 major brittle fractures ocurred in three of the steel box-girder bents. Since discovering the bent fractures, CTA inspectors found two long cracks in the bottom of the stringers. These cracks were found to originate at welded lateral gusset-plate connections. Approximately 1,800 lateral gussets are used in the 40-span system to attach lateral bracing. Each gusset plate contains a cutout to accommodate the vertical stiffener of the stringer. This detail creates a short gap between the cutout of the gusset and the vertical stiffener. An extensive investigative study of seven spans of the superstructure was carried out to assess the fatigue sensitivity of the stringers with the lateral gusset-plate connections. The study included a review of details used in the structure, field instrumentation and testing, an analytical review, in-depth examination of gusset-plate connections, examination and testing of samples that contain cracks, and the development of retrofits. The information collected during the study, particularly the field testing data, is reviewed. Reviews are also made of the fractographic examination conducted on a sample that contains a 4-in. crack and the in-depth inspection findings. As part of this study retrofits were developed to either shield the crack origin from stress or to increase the gap between the gusset-plate cutout and the vertical stiffener."
The correct name of the fellow who noticed the cracks was Hernan Solarte, P.E., a Rock Island RR bridge engineer, who received a commendation from the City of Chicago for noticing the problem. Some details from the Ed King article referenced above to follow in a day or so. Mr. Solarte is still active in the business - the firm he now works for had a lot to do with the recent Cajon Pass project for BNSF.
I have been reading this string and keeping quiet, but I think some things need to be said.
While I have never seen an episode of "Seconds from Disaster", I do have to take issue with the assertion that the barge hit (not a bump) should not have damaged the bridge.
The NTSB report clearly shows the impact point was on the pier under the north end of a 165' truss and the south end of the 140' TPG and on the center pier of that TPG. The TPG was, according to the report, built in 1909 to replace a truss span. The intention seemed to be to create a swing span. No machinery was ever installed. The south pier of the TPG is concrete. The south end was the expansion end, the north end was the fixed end, hence no direct anchoring of the span to the pier. It was fastened correctly.
The south end of the TPG "was displaced 38" by the barge and was subsequently destroyed when tran 2 struck the displaced girder" to quote from the NTSB report. That is hardly a "bump"
Please, when you are commenting on incidents such as this, it helps if you take a little time and consider what sources you are referencing.
I also recall most of what steve14 posted above about that disaster, and hence agree with him on that. (BY the way, ''TPG'' = Through Plate Girder.) I looked earlier and was not able to find the full report - maybe it was moved to someplace I'm not familiar with ? - the best I could find was the below summary of the NTSB report, which didn't address the precise issue here. Nevertheless, my recollection is that it was a definitely a fixed portion of the bridge that was distorted on the order of 3 ft. out of line by the barge tow's impact - I thought it was more like trestlework than a pier and the TPG, but my memory is not clear or certain on that. Simple consideration of the mass/ weight of that tow moving at a couple miles per hour tells you that when it hit that fixed structure, serious damage was going to be done - there's no energy absorption or attenuaiton device or arrangement on either one, other than the distortion and deformation resulting from the collision damage, which is what finally brought the barge tow to a stop.
RAILROAD-MARINE ACCIDENT REPORT Adopted: September 19, 1994 DERAILMENT OF AMTRAK TRAIN NO. 2 ON THE CSXT BIG BAYOU CANOT BRIDGE NEAR MOBILE, ALABAMA SEPTEMBER 22, 1993
NTSB Number: RAR-94/01 NTIS Number: PB94-916301
http://www.ntsb.gov/publictn/1994/RAR9401.htm
[EDIT]: Here's the NTSB's summary of the causes - note that all 3 of the principal causes are marine-related, not rail-related. As between some sensationalistic TV show and the NTSB, I give the NTSB a whole lot more credence [emphasis added - PDN]:
"The National Transportation Safety Board determines that the probable causes of Amtrak train 2's derailment were the displacement of the Big Bayou Canot railroad bridge when it was struck by the MAUVILLA and tow as a result of the MAUVILLA's pilot becoming lost and disoriented in the dense fog because of (1) the pilot's lack of radar navigation competency; (2) Warrior & Gulf Navigation Company's failure to ensure that its pilot was competent to use radar to navigate his tow during periods of reduced visibility; and (3) the U.S. Coast Guard's failure to establish higher standards for inland towing vessel operator licensing. Contributing to the accident was the lack of a national risk assessment program to determine bridge vulnerability to marine vessel collision."
[END EDIT]
Here's the link to the NTSB's list of ''Railroad Accident'' reports:
http://www.ntsb.gov/Publictn/R_Acc.htm
If someone has a link to the full NTSB report, that would be appreciated.
I don't think the program fabricated the idea that the barge moved a swing span that was not fastened properly. I'm having a look at the NTSB report.
It's funny how in the same forum we have slandered the NTSB and have now praised it.
Oh, and it was the train that destroyed the end of the bridge, not the barge. That's an important point of fact.
I should add that these shows often have additional research not included in the reports.
Anyway, here are some more documents:
http://www.usfa.dhs.gov/downloads/pdf/publications/fa-163b.pdf
EDIT: The original is still only in book or microfiche form.
A couple years ago, a U.P. train running on the ex-M&StL line from Chaska, MN to Merriam Junction, crushed a short (50’ long) timber trestle spanning a watercourse draining into the adjacent Minnesota River and dumped several cars into the water. Due to having only one customer on the line, U.P. abandoned it rather than rebuild the trestle. Interestingly, that same trestle was struck by lightning and set ablaze in the 1910-1915 era, and an CMStP&O freight broke through the smoldering timbers before the engineer realized the bridge was on fire.
On that same line, there is a much larger, multiple span deck girder bridge on stone piers spanning the Minnesota River at Carver, MN. In earlier times, the M&StL routinely had commercial divers enter the river and inspect the bedding of the stone piers. Over the last 20 years or so, one of those stone piers has settled unevenly, apparently due to the river scouring out the bedding for the pier.
Before operations ended, that pier was tipped toward downstream so that its top was about 12”-18” out of alignment. It was very visible as a large dip and offset in the bridge deck, and in just looking at the pier compared to the rest of the piers. I found it hard to believe that U.P. continued to use the bridge when the pier bedding was so obviously compromised. How could you be sure of the pier performance at any given train event when the condition of the pier was obviously changing over time? How many degrees can you tip a GP-38 before you concentrate so much extra loading on the tipped pier that it tips further?
Paul--I must have down loaded the report early enough to get the whole thing, because only the Summary shows on the NTSB web site now.
Aegrotatio--The TPG span was destroyed by the train, yes that is fact. The key point is that the barge moved the span over 38" so as to be in line for the train to hit it. With the force of impact of the barge, no amount of anchor bolts would have held that end of the bridge in place.
I don't really think anyone slandered the NTSB. Are you referring to Blue Streak 1's differentiation between an FRA accident report, which is confined to facts, and an NTSB report which brings in a great deal more analysis and recommended changes, etc?
If there was additional info developed for that show, it would be nice to see it and know who and how it was developed. As Paul said-- TV show vs NTSB, who ya' gonna believe?
Semper Fi
http://news.google.com/newspapers?nid=1817&dat=19931206&id=TTEdAAAAIBAJ&sjid=cKUEAAAAIBAJ&pg=6706,3198067
Sure, TV show vs. NTSB report, but be careful of the association fallacy. This isn't the only show you may encounter that adds extra evidence and research to a long-held problem. The thing lacking would be peer review, but just because it's on TV doesn't mean it's wrong.
Bucyrus On that same line, there is a much larger, multiple span deck girder bridge on stone piers spanning the Minnesota River at Carver, MN. In earlier times, the M&StL routinely had commercial divers enter the river and inspect the bedding of the stone piers. Over the last 20 years or so, one of those stone piers has settled unevenly, apparently due to the river scouring out the bedding for the pier. Before operations ended, that pier was tipped toward downstream so that its top was about 12”-18” out of alignment. It was very visible as a large dip and offset in the bridge deck, and in just looking at the pier compared to the rest of the piers. I found it hard to believe that U.P. continued to use the bridge when the pier bedding was so obviously compromised. How could you be sure of the pier performance at any given train event when the condition of the pier was obviously changing over time? How many degrees can you tip a GP-38 before you concentrate so much extra loading on the tipped pier that it tips further?
What I'd like to know is how often trains were put through in a day and how fast they would run. I know there would have been restrictions but----
Also what would that offset do to the piers next to the tipped pier----I'd love to have seen what kinds of side loading would have occured with, say, 15 cars loaded----
Any argument carried far enough will end up in Semantics--Hartz's law of rhetoric Emerald. Leemer and Southern The route of the Sceptre Express Barry
I just started my blog site...more stuff to come...
http://modeltrainswithmusic.blogspot.ca/
Some more details in the ''Seconds from Disaster'' vein, from -
http://en.wikipedia.org/wiki/Big_Bayou_Canot_train_disaster#Analysis [usual disclaimers apply - PDN]
An episode of the National Geographic Channel [National Geographic Channel, also commercially abbreviated as Nat Geo, is a subscription television channel that airs non-fiction television programs produced by the National Geographic Society...] documentary series Seconds From Disaster [Seconds from Disaster is a documentary television series that aired from July 6, 2004 to March 7, 2007 on the National Geographic Channel. The program investigates historically relevant man-made and natural disasters...] examined this accident in detail.
This analysis seems to me to be of a ''If pigs had wings . . . '' nature. It completely skips over the fact that 'but for' the towboat skipper getting lost and then hitting the bridge, the wreck would have never happened. Also, there's a circular fallacy here about barge traffic posing a regular hazard - if that had been a designated river channel, the points might have some merit - but it wasn't. So why should the railroad have equipped the bridge to withstand a collision from a marine tow that wasn't even supposed to be near there in the first place ? Note that of all the many recommendations made by the NTSB to the several agencies and organizations as a tresult of this tragedy, none of them pertained to this aspect. To suggest as the above quote does that jointed rails are better on bridges because they might be more likely to break if impacted and thereby trip the signals to red - and ignoring the other benefits of welded rail - is to invent facts and rationales where none exist or have actual support in reality. May as well say that the engineer should have run 5 minutes ahead of schedule - then the train would have been past the site when the barge impact occurrred.
Still looking for the full text of the NTSB report to see if it thought this even warranted mentioning, and what treatment it was given . . .
'Original Post' for this thread -
Murphy Siding Other than last year, when a bridge (or trestle?) on a shortline railroad collapsed while hauling something big for NASA, are railroad bridge failures rare?
I ran across this while looking for the NTSB report on the Amtrak Big Bayou Canot wreck. It's pretty instructive, I think, for the original question:
''What the Profession Can Learn from Failure of its Bridges.''
from
at - http://content.asce.org/files/pdf/HHNewsletterMay08.pdf
[It's 3 pages, approx. 369 KB in size]
There's a little table of 11 bridge failures over the 150 years from 1857 to 2007; the Ashtabula Ohio bridge in 1876 is the 2nd entry, and the I-35W bridge in Minneapolis in 2007 is the last. Notably, 6 of the 11 are railroad bridges; but the last one before the 1993 Big Bayou Canot Amtrak wreck was the 2nd attempt to bridge the St. Lawrence River at Quebec in 1916 - the other 5 in the last 40 years since 1967 are all highway bridges. This excerpt is also illuminating [emphasis added - PDN]:
''In summary, six of the failures were the result of a failed connection, two by ship impact, one by a compression member failure, one by scour and one by a train running off its tracks. The journals and newspapers of the time sensationalized each failure. Over time the profession modified procedures and specifications to minimize future failure. The Minneapolis Bridge failure, however, indicated we still have a ways to go before bridge failures are a thing of the past. Henry Petroski, Chair of the H & H Committee, has written extensively on bridge failures and has written as early as 1993 “that the cable stayed genre was a most likely candidate to experience the next major bridge failure.”
It is recommended that the training of Civil Engineers include an exposure to the History of the profession in general but more specifically in the study of failures and subsequent actions by ASCE and the specifying agencies to correct flaws in the specifications, design procedures and inspections.''
Finally, on the 3rd page under the heading ''Banner Images'' are a couple of paragraphs on the Kate Shelley Bridge, its Engineer, and its then-pending replacement. I ought to post a link to it in one of those threads, too . . .
Perhaps one of the most famous because of film recording of it's failure would be the Tacoma Narrows Bridge back in 1940.
The famous pictures of the automobile out on the bridge, and I believe it also showed a person trying to make his way back on foot to safety, while the wind has the bridge starting to sway and buckle until it finally tears apart and falls into the water.
I believe both bridge towers remained standing thru it all....The bridge was cable supported, and they finally snapped and much of it collapsed.
Quentin
blownout cylinder Bucyrus On that same line, there is a much larger, multiple span deck girder bridge on stone piers spanning the Minnesota River at Carver, MN. In earlier times, the M&StL routinely had commercial divers enter the river and inspect the bedding of the stone piers. Over the last 20 years or so, one of those stone piers has settled unevenly, apparently due to the river scouring out the bedding for the pier. Before operations ended, that pier was tipped toward downstream so that its top was about 12”-18” out of alignment. It was very visible as a large dip and offset in the bridge deck, and in just looking at the pier compared to the rest of the piers. I found it hard to believe that U.P. continued to use the bridge when the pier bedding was so obviously compromised. How could you be sure of the pier performance at any given train event when the condition of the pier was obviously changing over time? How many degrees can you tip a GP-38 before you concentrate so much extra loading on the tipped pier that it tips further? What I'd like to know is how often trains were put through in a day and how fast they would run. I know there would have been restrictions but---- Also what would that offset do to the piers next to the tipped pier----I'd love to have seen what kinds of side loading would have occured with, say, 15 cars loaded----
Here is a link showing the bridge at Carver, MN over the Minnesota River:
http://www.johnweeks.com/bridges/pages/rm01.html
In the first photo, you can see the misalignment toward the far end. In the bottom photo, you can see the defective pier, which is third from the left. In this photo, the river flows toward the camera, and you can see the pier tipped toward the camera as well. My impression is that the misalignment progressed significantly further than shown here.
During the final operations over the defect, trains were minimal in size, speed, and frequency. They would consist of one engine (GP-38) and 1-6 cars. Speed was very restricted over the bridge, to perhaps 10mph or less. The defect appears to involve only one of the piers. There is no indication of a structural problem with the integrity of the stone pier itself. Instead, it appears to be a case of the whole pier being tipped 5-10 degrees due to a loss of footing in the riverbed.
Trees float down the river and lodge against the bridge piers. Over the last 20 years of operation, the U.P. and previous owner C&NW allowed the trees to accumulate into a huge floating mass covering maybe an acre or more. Then the company would stage a rail crane and grapple on the bridge to pick the trees out of the mass, and place them on the downstream side of the bridge. When these tree massing events reached their maximum, they apparently restricted the river to a narrower flow, which accelerated the bottom scouring around the affected pier.
I know that yard tracks can become shockingly misaligned and still pass trains without derailment. But I found it rather surprising that the company would accept running trains over this bridge defect when is was obviously in the process (although a slow process) of developing abrupt, catastrophic failure. Moreover, the consequences of reaching that failure point while riding over it in an engine would be quite dreadful for the crew. Ironically, though, the eventuality of a pending catastrophic failure of this bridge was precluded by the abrupt, catastrophic failure of a small trestle only about mile south, which ended operation over this line.
As promised - from Trains, June 1986, Vol. 46, No. 8, "Disaster du Jour, and other stories", by E. W. ‘Ed’ King, Jr., pp. 30 - 36, at pg. 35, cols. 1 and 2, and pg. 36, col. 1:
[Several paragraphs omitted - PDN]
*The ''Jesse James'' coaches were ''steam-heated, 2500- and 2600-series ''Jesse James'' (or ''Harriman'') open-window coaches from the mid-1920's. Some commuters swore that there were holes in them from bullets and arrows.'' - per pg. 32, col. 1.
IIRC, there is a Mississippi River bridge whose location escapes me (Vicksburg?)-a cantilever, I believe-that has/had one pier out of alignment almost from the day of opening. Apparantly it's not too noticeable...but just knowing that would always give me pause before crossing (but I get nervous when it comes to heights, anyway...)
Paul--Thank you pulling out all of this trivia (bridge geeks like this stuff) and clearing up the "basis" of the claims made in the TV show. Sensationalism over substance. It would be interesting to know who the people were that developed these opinions.
I can send you a hard copy of the report if need be. The report makes note of the CWR over the bridge and that the signal system was not interrupted by the barge hit but offers no opinion on whether jointed rail would have come apart. This is hardly suprising. One of the many examples we use in the AREMA Bridge Scour seminar shows a bridge where the roadmaster had gone over suring a severe weather inspection and wanted to run back over the same route before letting trains go. The diapatcher argued with him saying his board showed all green. The roadmaster won and came back to the bridge which he had gone over only a couple hours before to find 2 of the 4 double track TPG's in the river.
The question we ask is "what color are the signals?"
We have many other examples of scary things you find on bridge inspections in AREMA's Bridge Inspection seminar also.
Kevin C. Smith Bucyrus On that same line, there is a much larger, multiple span deck girder bridge on stone piers spanning the Minnesota River at Carver, MN. In earlier times, the M&StL routinely had commercial divers enter the river and inspect the bedding of the stone piers. Over the last 20 years or so, one of those stone piers has settled unevenly, apparently due to the river scouring out the bedding for the pier. Before operations ended, that pier was tipped toward downstream so that its top was about 12”-18” out of alignment. It was very visible as a large dip and offset in the bridge deck, and in just looking at the pier compared to the rest of the piers. I found it hard to believe that U.P. continued to use the bridge when the pier bedding was so obviously compromised. How could you be sure of the pier performance at any given train event when the condition of the pier was obviously changing over time? How many degrees can you tip a GP-38 before you concentrate so much extra loading on the tipped pier that it tips further? IIRC, there is a Mississippi River bridge whose location escapes me (Vicksburg?)-a cantilever, I believe-that has/had one pier out of alignment almost from the day of opening. Apparantly it's not too noticeable...but just knowing that would always give me pause before crossing (but I get nervous when it comes to heights, anyway...)
I can understand how experience can judge how much misalignment you can run a train over without significant risk of derailment, and thus why some degree of misalignment is often tolerated. And, if there were a permanent misalignment on a bridge, simply due to a construction mistake, they might just live with it.
However, this misalignment on the Carver bridge is clearly the result of a progressing structural failure of the bridge. It is hard to believe that would be tolerated at all. Bridges are inspected to seek any indication of a failure that might occur because once the failure begins, it might progress as an instantaneous collapse with no further warning.
About two miles downstream from the Carver bridge was another bridge over the Minnesota River that carried the Milwaukee Road original Hastings & Dakota RR. That was a steel through truss center pivot swing bridge. Around 1988, I noticed that the bridge was obviously in the process of falling over due to a tipping of the center support that carried the swing bearing. This was an undermining of the riverbed just like what is occurring at the Carver bridge today. With the H&D bridge, I could see the tipped pier, one of the end roller bearings lifted off of its support base, and some of the tension bars coming off of the center “A” frame were buckled in compression. Clearly, the bridge was slowing falling over into the downstream side of the river.
By that time, that Milwaukee line had been abandoned and converted to a trail, so I called the state DNR and told them the bridge was falling over. They poo-pooed my report as being not credible. They said they routinely had commercial divers inspect the river bottom for evidence of scouring and pier undermining. They told me not to worry about it because they had engineers and bridge experts who would make sure that the bridge was safe.
In 1998, that bridge suddenly began to tip faster day by day, giving sure indication that it was going to fall over. So the DNR blew it up for safety. It was a tragic and needless loss of a magnificent structure dating from the 1890s, and a treasured feature of interest on the trail. So that was a catastrophic bridge failure in very slow motion. It took over fifteen years from start to finish.
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