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Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...
4

Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

(OP)
This particular bridge has been the subject of many posts in this forum over the years. Well, it appears that they're finally going to do something that they hope will resolve the problem. Note that they are only raising the bridge eight inches, increasing the clearance from 11'-8" to 12'-4". Not sure how much this will help, but it's the best they can do without completely replacing the bridge and re-engineering the rail route.

North Carolina’s Infamous ‘Can Opener’ Bridge May Decapitate Trucks No Longer

An 11-foot-8-inch railroad overpass in Durham is being raised after years of viral videos showing it lopping the tops off of vehicles.


https://www.huffpost.com/entry/can-opener-bridge-d...

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Are they raising the bridge or lowering the roadway below? With only two weeks for construction I have to believe it's the latter.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Quote (azcats)

Are they raising the bridge or lowering the roadway below? With only two weeks for construction I have to believe it's the latter.

According to this Atlas Obscura article, there's a sewer right below the roadway. My bet is that they're lifting the existing span and raising the abutments slightly, then re-grading the tracks on either side. But, we'll know for sure soon enough.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

That's probably the limit on how much the tracks can be raised without completely redoing the entire overpass to make sure the trains don't hang air going at their maximum allowable speeds.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Not affecting the grade crossings on each side of this location is probably the highest priority followed by limiting the maximum incline on each side of the bridge.

I hope the only reason for this is pedestrian safety as it is otherwise a national treasure in the art of paying attention while driving.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

8 measly inches.. I hope it helps. Those air conditioner sweeps will probably still happen. LOL

Keith Cress
kcress - http://www.flaminsystems.com

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

My guess, based just on what's written above, is that the bridge will be replaced with one that has less depth but the track grade won't be altered. New abutments could have already been placed using jump spans on either side of the main span to allow the abutment excavation and construction. Perhaps poured weeks ago and now fully cured.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Sidney Australia got tired of repairing tunnels, so they installed these difficult to overlook stop signs projected onto a cascading sheet of water, all triggered by overheight vehicles.



RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

The interior of the tunnel is always relatively dark, making an ideal backdrop. There is also a manned station near to that water curtain which is where the monitor those photos were taken is. Unlike the tunnel, the underpass has nearby alternates so when it is blocked there are options, making an expensive 24 hour manned warning overkill for the situation.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

One of my office mates lives in Durham. He is very familiar with the “can opener” and the years of entertainment the truck drivers have delivered.

Good Luck,
Latexman

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

"...expensive 24 hour manned warning..."

You've incorrectly associated two somewhat-related facts, linking them incorrectly.

Tunnels have staff to monitor traffic anyway, no matter if they have a Water Curtain or not. Especially if oversized trucks are constantly crashing into their tunnels. The staff would have to be stationed near the tunnel entrances for obvious reasons.

The triggering of the Water Curtain itself is obviously fully automatic; clearly it has to be. As a stand alone warning, it need not necessarily be 'expensively manned' as you've implied. Even if it needs to be reset manually, that's a ten-minute job, not 7 hours extracting the 3rd wedged lorry of the morning.

The Sydney tunnel will need significantly fewer staff overall if they're not spending their days extracting oversize trucks wedged into tunnels by inattentive bogans. The Water Curtain has presumably led to a dozen tunnel staffers being made redundant.

If one of the few remaining Sydney tunnel staffers happens to wander over after the system has been triggered, it would be to scold the driver, take away their Crown Lager, and assist them in backing up in heavy Sydney traffic.

And finally, if an underpass is overly bright, then the Water Curtain water could be tinted black to enhance contrast.

...Or they can lower the road by eight inches.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

The only thing that makes the water curtain possible is 24 hour watching to see that it functions. The fact that there is a monitor nearby was the first and most basic requirement, no matter the other duties. If the water supply fails or the lamp fails then someone has to fix that. It cannot go months without a look. The bridge gets about 1 truck a month; only about 1 per year required extraction. So the bridge would move from zero people to at least 3 full time on duty.

The water curtain being tinted black would absorb the light projected on it. Just water will not stop drivers any more than the majority that run the red light who strike the bridge.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

"The only thing that makes the water curtain possible is 24 hour watching to see that it functions. ...If the....lamp fails...

Yes of course, just like traffic signal lights. Every signalized intersection needs at least three full time staff.

ponder

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

But this is a railway bridge no?

They really don't like being run into as they usually need to check the tracks each time to make sure there isn't a risk of de-railment and stop trains until it's done. At least that's what happens in the UK....

A water curtain idea sounds like a proportionate response to me.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Littleinch
This bridge has an armored Beam in front of the bridge on a separate structure to do the can opening

Hydrae

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Makes it better. I hope they raise this as part of the work! Wonder what margin they allow on the bridge vs barriver.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

That particular overpass even has its own website http://11foot8.com/ The barrier is pretty beefy, but debris can still be seen hitting the trestle and shaking it. The site claims there's been at least 147 collisions at this overpass. The last was in June of this year.
http://11foot8.com/speeding-semi-gets-smashed-up-a...

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

This is the most recent crash accident there, and you can still see the trestle still got hit by something on the bucket truck and it bobbles a bit.
http://11foot8.com/bucket-truck-gets-chewed-up-at-...

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

(OP)
I watched several of those bridge videos (from the links above) and it's amazing how many people run the red-light at the intersection next to the bridge, including many of the trucks that crash into the barrier. It's like the stop-light is merely a suggestion.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

There's one video where the rental truck makes the turn away from the overpass, but, for some reason, decides to try it anyway, and comes back, and since there's a video...

You would think ANY rental truck company in the area would WARN renters to stay away from that bridge; but maybe that's a way to total the truck and get insurance money to buy a new one. I recall a couple of videos I watched a few years ago where the barrier cleanly zippered the tops of some trucks, but I guess that's the luck of draw and how much the truck was loaded down.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

It's fun watching that. One issue clearly is that the traffic lights on the bridge seem to bear no relation to the over height warning. Sometimes they're green, sometimes they're red.

The FAQ section of the website says there are many warnings and signs before the bridge but even so....



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

This saddens me a bit. My wife and her siblings all did their undergrad degrees in NC, so a couple years ago we all went down for homecoming and to visit her brothers at Duke. They're a big sports family and *really* into school spirit, some of which they were hoping would rub off on me during this glorious weekend in the south. Well, I don't give two hoots about my own alma mater, much less somebody else's. They weren't too amused when the only thing I got excited about all weekend was seeing "that bridge from the internet."

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

LI,
The traffic light is the traffic light for the intersection. The warning sign starts blinking when the bridge detects an overheight truck, but unless they know that the blinking is because of them, they'll see it only as a general warning and not applicable to them.

Of course, there seems to be a very high incidence of red-light running, so those people will obviously ignore the overheight warning, just because they're running the light anyway.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

I think the rental trucks are typically not from the area.

The light turns red on the initial detection, turning green to allow the over-height vehicle to turn at the intersection; if it stayed red then no traffic could move. There should be at least one red cycle before an over-height vehicle enters the intersection.

On Google maps one can take a tour down that road. There are many signs leading to the bridge; they seem to fail for those who forget they have a truck or trailer behind their seat.

Some think the trestle shakes - there is a walkway on the side of it that cantilevers and the railing and walkway do shake; I expect the bridge does not as it does not deflect when a locomotive rolls over it.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

The red light is strictly the intersection traffic light and has nothing to do with the trucks. The humongous blinking letter sign is what's supposed to warn the trucks. I've only seen one video from 2019 where the sign didn't blink. Note that most of the red lights you see are where the trucks and other traffic are running that red light.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

The red light was attached to the over-height sensor to stop traffic when the initial over-height item is detected and give drivers the option to think. I assume most do and make the turn. It has to turn green sometime.

"The signage is good, and the vast majority of truck drivers notice the problem and avoid the bridge. Large signs alert driver to the low clearance several blocks before the bridge. Half a block before the trestle, a sensor detects overheight vehicles and triggers an LED blackout warning sign that was installed in May 2016. That same sensor also triggers a red-light phase at the traffic light directly in front of the trestle (installed in March 2016), so the driver has 50 seconds to read the warning sign next to the red traffic light and consider their next move."

http://11foot8.com/faq/

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

(OP)
I guess it's possible that the 'locals' know that when the warning sign is flashing AND the red-lights are ON, that the cross street's light are also red and so they just take advantage of the situation and drive through the intersection knowing that it's 'safe'. If the city wanted to make a little extra cash they would assign some patrol cars there to not only ticket the drivers who ignore the warning signs and hit the bridge, but also all of those other drivers who blow-off the red-light thinking that it does not apply to them. After all, a red-light is a red-light, and when it comes to traffic laws, it has to mean the same thing to everyone. And if they wanted to get really bitchy, the city could install a red-light-cam and automate the entire process.

BTW, even if they do manage to successfully raise the railroad bridge eight inches, they will still need to keep all of the signs and warning systems in place, only changing the clearance warning from 11'-8" to 12'-4". And there will still be crashes, albeit less frequent (they hope), than now as there are still a lot of trucks out there with loads taller than 12'-4".

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

I was driving a few hundred feet behind a camper going under this bridge. The lights were flashing and he/she did not seem to notice. Watched his A/C unit get ripped off the top.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Signage is often a big problem, particularly something like this. When do you notice the sign is blinking; was it blinking all the time? "You talking to me?"

A cool high tech solution might be to have a steerable high-intensity light that shines directly at the truck driver, "Yes, you, you numbskull; your truck is too tall for the bridge!" Or, maybe, it just flashes, "Turn away from this light!" However, I saw one video, out of about 10 viewed today, where the sign didn't flash, possibly because the truck was JUST BARELY over the limit.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

(OP)
And the local authorities also have to be careful to not make the height detector too 'conservative'. After all, if it can be shown that the detector is forcing the rerouting of commercial vehicles unnecessarily, this could lead to official complaints if not actual legal challenges. And again, all of this talk about 'fixing' the bridge, will only mitigate but not eliminate the problem.

BTW, does anyone know what the minimum overpass clearance is on say the interstate system? What about municipal streets? I realize that if there are such standards and or even regulations, that this particular structure would have been grandfathered years ago, which brings up a question for the people out there might actually know. How much 'tinkering' with this bridge can they get away with before they reach a point where they are forced to simply replace it altogether? It's like where I live here in SoCal, in a desert environment, where wild fires are frequent. When our residential development was built back in the mid-to-late 70's, they were still allowing wood shake roofs. Now every 5th house or so had clay tile roofs (ours is one of those) but the rest were wood. Since then the laws have changed and wood shakes are no longer allowed, but they couldn't go in and force home owners with wood roofs to replace them. However, they did pass an ordinance that if a home owner attempts to replace more than a certain percentage of his wood roof with new wood shakes, then he must replace all of it with some sort of fireproof material. This protected people who needed to only make minor repairs while also protecting the community from people who replaced 90% of their wood roof with new wood shakes while saying they were only doing a minor repair. I'm not sure what this minimum percentage is as it was never going to be an issue with us. Since we moved into this neighborhood 32 years ago, virtually all of the wood roofs have been replaced with fireproof materials, but there are still a few holdouts who have gamed the system by only replacing small sections of their roof every couple of years. A few of them have probably replaced their entire roof more than once over already, but they're resisting out of principle, I guess. I suspect that if they had just bitten the bullet the first time there was any significant work done that they would saved money in the long run, to say nothing about getting a discount on their homeowner's fire insurance. And for the record, within our development, which this story was related to, there are 134 homes, and as I said, there's probably no more than five left with wood roofs.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

This overpass is about 100 years old. AFAIK it predates the US interstate system.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

The red light is not a height control. It is not held on as long as any over-height truck is anywhere in the area. The FAQ from the guy who lives there tells that. It triggers as an over-height vehicle is detected, but it's got to turn green sometime or it will just block the entire street.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Would it be an effective deterrent to install those hanging overhead clearance bars things that are used in parking garages? They could put one at each of the 3 sides of the intersection, so a truck would get clunked away from the bridge and hopefully stop at that point.

Edit: Maybe not at all three sides since innocent trucks traveling parallel to the bridge would be getting bonked unnecessarily (good point by 3DDave), but having one on the bridge side of the intersection would probably help a little bit at least.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Those clanging banging noise making things that would irritate the neighborhood for blocks around for the 99.99% of delivery trucks that don't head for the bridge? Making the sound of a good bashing all the time instead of just when someone deserves it? Sure. Punish all the people.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Didn’t realize they were a noise issue. I was imagining something like this:

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

My grandfather always said that you can't make something idiot proof

The signage is an interesting example of a doomed attempt to accomplish that. Arrows related to the hazard point in literally every direction. I wonder how many hours have been spent in staff and council meetings trying to decide which way the arrows should point

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

It better make a lot of noise to get through to drivers that have ignored a bunch of signs and -exactly- that same bar across the roadway that they keep hitting at the bridge.

This bridge has been investigated for nearly 80 years.

As if in 80 years no one living there was smart enough to realize a simple fix would work.

This signage seems clear -

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

But, that sign can be easily obscured by a truck in the RH lane doing the correct thing, while the victim (?) blithely carries on in the left lane. It also depends on the driver actually paying attention and assumes that the driver actually remembers the height of the truck they're driving, which seems particularly difficult for a rental truck. Half the time, I can't remember the color of my rental car the next morning, and something the rental counter person told me 3 days ago, like the height of the truck, might be long gone.

I certainly wonder whether some sort of hanging sign at the height limit might have been more effective. I would have thought that a sign that said, "Turn away from this overpass if you hit this sign" might trigger some sort of survival instinct.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

At the head of the street are a pair of 11'8" warning signs, one on each side. The limit signs are duplicated at the bridge.

The correct answer is - if your truck is over 11'8" don't go across the intersection.

Rental trucks usually have the height placard on the dash board in front of the driver and on the side of the box where it is properly readable in the side mirror.

1000 trucks slamming into a noise producing obstacle and doing some damage to the trucks as well is a poor way to stop the 1 from hitting the barrier.

This isn't an office park or a parking structure. It sees truck traffic all the time. I'm sure that 80 years of deliberation came to the right conclusions that preventing non-injury accidents is primarily the responsibility of the drivers and that providing multiple warning signs, flashing warning signs, and a striped beam that's been damaged, should be enough.

If the driver isn't paying attention to a certain collision situation they need to not drive anymore.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Apparently, the bridge bit another one, just posted today, but occurred almost 3 weeks ago! http://11foot8.com/excavator-on-trailer-bites-back...

Again, the lights stay green, but the sign clearly flashes the warning.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

The video starts with the light red, indicating the red light was triggered to stop the vehicle and give the truck driver an opportunity to look around. The truck was in the right lane, next to the turn sign so his view of that was not blocked.

I rank this the same as people who let their truck and trailer run into the lake and sink at boat ramps.

To amplify, did this driver look at the flashing sign between the traffic lights, then look around and say "I'm the only truck here, so it cannot possibly be referring to me."? I assume he can see the light is green and is paying attention to traffic lights.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

2
A more anemic bunch of warnings you couldn't come up with! Truly pathetic.
The bridge is a menace and obviously way under national norms. Because of this they should make an extra effort to warn drivers.

1) They should use a laser scanner to sweep the streets and find the approaching potential victims at a distance.

2) The warning should be nearly blinding red including some RED Strobes.

STOP - OVER HEIGHT VEHICLE! Not some low contrast white garbage sign.

Saying they've provided adequate warning when they haven't is a poor argument.

You get more warning in a car wash that: "JIFFY WAX is being applied!".

Keith Cress
kcress - http://www.flaminsystems.com

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

In this mornings The News & Observer:



Good Luck,
Latexman

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Really, just block the underpass completely. That's the only effective "warning." Sure, it means that emergency services might have extra miles to go if the grade crossings are blocked by a train, but that's the breaks to save a few ignorant drivers from hurting their vehicles.

Wasn't a red strobe light starting epileptic seizures a critical part of Andromeda Strain? Seems like a poor idea to put a someone into an epileptic fit because another person in a truck is near to them.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

3DDave... what if we got a few dead horses and suspended them from just the right height so they would make gentle thudding sounds that would not disturb the neighbors, cause seizures, or require a local launch control centeresque command center for monitoring their functionality?

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Ha - then the drivers of the trucks would not hear them and they would still hit the bridge guard beam.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Just keep the next truck roof that gets zipped off and attach it to the guard beam. That would get a truck driver's attention no problem.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

I do like that, though I think collecting the A/C units and putting them on spikes would serve as well.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

"...a poor argument."

This particular forum does seem to attract strongly-held opinions whose formulation is inexplicable.



RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Poor arguments are those that propose a fix, but then don't detail how that fix will flawlessly work. Given the number of other structures around the world and the number of crashes and damage from them, if there is a good fix the person with that idea will be wealthy beyond imagining. Unless the fix is far more expensive than the losses. Which is poor engineering at best.

Share those cost-effective solutions that the proposer has personally sold and has demonstrated to eliminate all such problems. No fair picking ones that are proposed to solve the problem.

Problem statement - prevent all trucks from taking a path that is open to cars.

Ready, set, GO!

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Quote (3DDave)

Problem statement - prevent all trucks from taking a path that is open to cars.

Solution: Install bridges at a height of 11'-8" winky smile

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

That only stops their completing the path, not from taking it.

Good try.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

That's why you have the tow truck standing by to remove the stuck truck and allow the cars to continue to flow.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Those trucks can get pretty well stuck; there's at least one video where they had to deflate the tires to get sufficient clearance to move the stuck truck.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

That's 10,000 tow operators on 24 hour standby; though it is not a universal fix. Some of the collisions have destroyed the bridge. I saw one in Florida where a back-hoe clipped through all the bottom strands of the post-tension cables on one of two beams of a pedestrian walkway. The road was closed over fear of collapse for about 2 weeks until the bridge was demolished. Makes the FIU response look especially poor as the visible volume of damage was not nearly as much.

Another similar collision not only tore out the post-tension cable, but also punched out the entire web of an outer concrete beam.

The reason for all trucks is that in New York state there is a no-trucks parkway that would easily cost half a billion dollars to replace all the overpasses, apparently designed in the 1940s, and truck and semi drivers routinely ignore no-trucks signs and either get stuck, get demolished, or creatively, straddle the lanes to position under the high part of the archways.

The finders fee for avoiding a half-billion dollar fix would be a nice retirement. And would go far in keeping 36 ton trucks off of 8 ton pedestrian and light traffic bridges.

Another great source of revenue is keeping both heavy equipment such as high lifts and backhoes from being overheight (above 16'6" Federal highway limits) but also dump trucks from driving about with raised beds that seem able to reach 30 feet. Maybe all overpasses need to be 50 feet, just to be sure. In any case, the dump trucks are an especial menace as they stop the truck bed in under a second, can bring down highway spanning steel sign supports that can easily crush most cars, can punch out structural members force long term overpass closures. All because the driver has no situational awareness.

The challenge there is simple, but the circumstances are not.

The driver will cut wires and do any splicing required to stop any alarm or flashing light from distracting them on the job site where moving the truck with the bed up is necessary. I've seen it done on military equipment by enlisted workers where they "accidentally" damaged the warning beepers. Over and over again.

It can also not add any cost or have any other failure modes. Trucking firms don't want to pay for upfront or maintenance costs. It will have to last at least 30 years.

And it cannot depend on the driver to take any other action.

But it has to guarantee the bed is fully down on the stops when it is on the road, even if the PTO is engaged and the Bed-Up switch is on.

This is separate from the bridge challenge, but it would also avert injuries and deaths every year and hundreds of millions of dollars in infrastructure and personal property damage.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

"...how that fix will flawlessly work."

Ah, I can now see where your assumptions have gone wrong.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

The current signage and warning solution is not flawless. It works, but not every time. Yet many feel that is not acceptable.

The only choice for improvement is to make a flawless solution. So my assumption of what is required by those railing for change is perfectly correct. The only change I'd push for is a barrier wall to protect pedestrians from ejecta; the damage to vehicles and their occupants currently doesn't bother me at all.

We know that other bridges with greater clearance than the planned alteration to this one get hit nearly as frequently; they just happen not to have their own YouTube channel to remind us of that every few months. So raising the bridge to any height is a flawed approach.

But, if one accepts failure in spending more money without benefit, then maybe that's a bad assumption.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

"So my assumption....is perfectly correct."

That's perfectly incorrect.

Edit: Extraordinary claims require extraordinary evidence.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

They would be better restricting the width of the two lanes so only cars can get through.

I used to drive 40 ton artics in my youth and around Scotland there are a fair number of similar restricted bridges which regularly get hit with lorry's that are not in the know. Quite a few of them listed as cultural items which need protection.

Drivers will see and not go near narrow openings. They can see the limitations of the front of the vehicle, they can't see the roof. 4 elephant posts both sides of the bridge with a car width between them will do the trick. Two next to pavements stopping them going on it and the other two in the middle restricting the width. Also has the bonus of giving a pedestrian safe heaven in the middle while crossing.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

VEIBLL - then you should be able to write a concise statement to the contrary rather than gainsaying the negative.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

So they won't hit the bridge but now have road level impacts with obstructions that prevent emergency vehicle access? In the USA roads typically don't have posts directly in the middle. Distracted car operators now have something to hit that they did not expect. Smashing.

Looks like a no-fail plan; here it is in action:
https://www.dailymail.co.uk/news/article-4600048/J...
https://www.alamy.com/stock-photo-white-panel-truc...
https://www.dailymail.co.uk/news/article-2051302/L...
https://www.driving.co.uk/news/news-trucks-damage-...
- "Drivers ignore 6ft width restriction sign", "in the past week alone, three trucks have become stuck in it."
- three a week is not an improvement over the current situation.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

The internal logic (sic) that was used to reach (for example) this conclusion, "So raising the bridge to any height is a flawed approach", clearly indicates that rates of occurence (i.e. numbers) are not being considered.

That's a blindspot that is a subtle form of innumeracy. A sort of 'Black vs. White' digital processing that is effectively a Random Opinion Generator. This type of cognitive bias allows arguments to be made that are grammatically correct, but reach the most extraordinarily bizarre conclusions.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

The goal is avoidance of impacts. Changing from X per year to Y per year, where X ~ Y, at some large cost is a blatant form of innumeracy.

Perhaps you could do the work and see what the change in rate was from the addition of the red light and blinking sign. That would likely show that the desired reduction, but not elimination, has already been achieved but, since no one has stated their lower limit acceptance for collisions, the clear assumption has to be that that number is zero. Which won't happen.

I think you don't know what "(sic)" means.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Why not install a Railroad Crossing Arm that doesn't budge until the vehicle that is the height hazard is out of range?

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Because the detector has to be far enough back that a truck at full speed has time to stop; if cars are already stopped to allow cross traffic and a truck trips that detector, the truck will never be able to move because the cars ahead of it will have a solid red light/crossing arm blocking their way.

Now, as the Australian experiment goes, 24/7 manning of the bridge could put a person there to handle this deadlock, but I think the budget for 3 shifts a day of two people to cover for lunch and bathroom breaks is more than they want to spend.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Raise the bridge but don’t change any of the signage or the warning system. The number cases where the truck is only 3-5 inches too tall will be greatly reduced.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Works fine in uk, ambulances have a remote that drops the posts in middle if required.

Fire brigade have zero chance getting under it anyway. Police cars fit through.

Two bracket bollards are different to narrowing streets and medieval corners.

Mind you UK drivers can do roundabouts which I suspect would be leathal in the USA.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

"...the clear assumption has to be that that number is zero."

Nonsensical assumption leads to nonsensical opinions.

It's one thing to pretend to be daft on a social forum for entertainment purposes, but I really hope that you don't do serious engineering work like that.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

VEIBLL - Then what number do you pick? How much is it worth? How often do you resort to insult instead of analysis to force your opinion on co-workers? That's not an argument, that's bullying.

Alistair - If a driver cannot notice two entire buildings are too close together then they won't notice small items planted in an unexpected location. A remote? Come up with a link showing these in the middle of London streets for truck control. There are traffic circles all over Washington DC; US drivers handle them fine. But the number of low bridge collision stories in merry Old England is stunning, so you haven't much evidence of any superior skills there.

Edit: Used correctly bollards are a great idea for this https://www.youtube.com/watch?v=IELpd43PMvk Instead of damaging over height vehicles they can potentially damage everyone else.

Edit 2: Cambridge put rising bollards in. Then Cambridge took them out because of continuing damage. Huh. Who would have guessed? https://www.cambridge-news.co.uk/news/cambridge-ne... Now they use Big Brother ticketing cameras.
"An ambulance, on the way to a treat a fallen child in the city centre, was forced to make a detour because the bollards in the road failed to go down." Perfect example.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

They manage and they are not small.

And painted black and yellow.

https://www.access2time.co.uk/security-gates-barri...

They are also used to control access to pedestrian areas.

And London has loads of them mainly used to protect against lorry attacks against pedestrians. They are tested for a 40 ton artic hitting them at 50 mph.

Problem with English roads is most of them are chariot sized or horse and cart same with road curvature in market towns. There are loads of bridge hits as well, there is also the problem with double decker buses which when they do hit tend to kill the whole of the top deck.

Most commercial drivers in the SE of England are not locals. Its a 200 year old road structure with no space to expand the road width.

I can't see them getting rid of hydraulic bollards any time soon.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

(OP)
Yes, I've often driven around the Midlands, places like Nottingham and Leicester, or out west of London to places like Salisbury and Andover. and what always struck me was that for a country famous for some very large cars, like Rolls' and Bentley's, they had some of the narrowest 'country lanes' I've ever seen, often with hedgerows that would have made it impossible for two cars like that to pass each other. I always rented something small like a Mini or one of the smaller Fords, simply because of the narrow roads and having to find places to park, particularly in older cities like Cambridge or Grantham.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

You just need to look at the maps of these place in the 1600's and then 1700's then 1800's, London benefited of a reset with the fire of London. Most places didn't.

Country lanes for hundreds of years were only for the transport of product to the farms there was no need of more space, traffic only went in one direction depending on the time of day. These days some of them are main routes between population centres.

Up north in Scotland we didn't benefit from the Roman roads but due to much lower population density the roads are much less restrictive. What we do have though is a load of railway bridges of none standard height which do cause problems. More than half of them aren't even active but are of historical importance. All of them are made out of arched brick so there is no chance of adjusting the height to add an extra 8" on.


large cars/lorry's have only existed for the last 100 odd years, the road network start evolving with the Romans in England.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

"Then what number do you pick?"

That's where engineering analysis comes in, in a small report and/or spreadsheet. As opposed to taking extreme positions, as you have.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

VEIBLL,

Ah, blame shift to a "report". Very few such reports get done. Engineering is generally to maximize or minimize, based on some resource limitation. So one either picks an amount of money to spend and gets the most for it or picks an outcome and tries to spend the minimum to achieve it. The latter was the case for every proposal and contract I worked on for the DoD.

They are spending $600k and closing the underpass for 2 weeks solid. I expect both of those numbers exceeds the last 20 years expense to the city for responding to crashes and the total time the underpass was closed while jammed vehicles were removed.

Based on your economic experience, would you agree that this paying off, without including the time-value of money, in more than 20 years is a wise investment?

The sad thing is this won't prevent -all- crashes. As I previously pointed out, there are many bridges that share the new height or are higher which are hit regularly. They aren't as noted because they don't have a website dedicated to them. So it is likely to stretch this investment payback to 30+ years.

To demonstrate that is expected, they are installing a new crash beam.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Just found this:

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Horizontal and vertical are easy, the diagonals look like it will take another few pages to get.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Looking at the Sydney Harbor tunnel -
1) The water curtain stop sign is manually operated. I assume this is because traffic speed is variable and they don't want a car getting rear-ended while stopping by the truck it is actually for, so they carefully observe the monitors to operate it at exactly the right time.
2) They say they decreased the incidents by one third simply by instituting a 2000 Australian dollar fine; they also pull the license for 3 months.
3) This is not for ordinary trucks; this is for legally over height vehicles, so it's a tiny fraction of traffic.
4) The sensors on warnings like at the Durham bridge that are ahead of this are set below the marked tunnel height, so drivers of vehicles don't know what the limit actually is; gets fined 2k anyhow.
5) Because it's last-ditch, an onsite crew has to be available 24/7 to block traffic while the over height vehicle backs up to a place, 500 meters earlier apparently, to where it can divert.
6) My favorite, one trucker was going to get a fine because a thin sheet-metal panel, about 500mm square and <1 mm thick was peeled up and waving in the breeze on his ordinary height semi trailer. And lose 3 months of work.
7) Even with this system there are still truckers who manage to hit the tunnel; they just have to be far more creative, such as letting the load slide partly off the side but still be too tall to get lifted by a fork truck back into place.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

"1) The [Sydney tunnel] water curtain stop sign is manually operated."

I assume that you picked that up from the online video, where somebody presses the big red button. Did you consider the possibility that that's just a demo deployment, while the film crew were onsite?

Automatic overheight sensors are not a technological leap as you have erroneously concluded. They're used everywhere. Your objections are extraneous.

I can't be bothered to find the error in your financial conclusion, but it is obviously incorrect. As evidenced by them proceeding with the project.



RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

No I picked it up from the video where the guy working there says "We activated the curtain after the truck passed the automatic warnings." This before they spent 30 minutes clearing the resulting traffic jam, which is more time than the steel beam usually requires at this bridge.

I know you love the idea, but how does it work with bright daylight behind it on this bridge? ENG101 for feasibility; needs to work in all expected conditions.

Where do you get the idea I think height detectors are such a leap? Getting them to trigger the deluge at the exact right time when they don't detect either the speed of the vehicle or understand what will happen to surrounding traffic is what is difficult. Not so much when there is 24 hour manning to watch the tunnel and people can do that.

If it automatically triggers for a 45 mph truck, the sensor needs to be far enough back to stop, but if the truck is only going 10 mph then it needs to be just before the bridge. I'm sure you saw the video where a truck stopped a couple of feet from the beam and then gave it the gas. Should it just stay on continuously blocking all lanes as long as a truck is somewhere on the street?

Give it some thought as to why it's installed in only one place in the world when it is such a great idea.

It's $600k to raise the bridge 8 inches and is likely because even one pedestrian injury judgement will exceed that and in court they can now say they tried, but it won't stop the collisions. Those RVs are still going to lose their AC units and a lot of box trucks are still not going to fit.

Economically, since the railroad hasn't had any costs because of the collisions, isn't this a charity donation? (Figures - original cost of collisions was zero. Ongoing cost of collisions remains zero. $0/$600k = benefit = 0. I think I've got the finances of this calculated correctly. At an historical $0/incident how long to recoup that $600k?

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

LOL, it's not hard to detect the speed of a vehicle, at all....

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

It's hard to predict what speed the vehicle will be going as the driver reacts. LOL.

It's the inverse of the self-driving car problem, which still sees vehicles slamming into stationary objects. Which is why it is manually operated in Sydney. At the only installation.

But if you are so smart, then you can make millions selling your solution to the problem and make me feel bad at the same time.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Jumping into this one late, but I have to agree that the water curtain isn't practical in this case. Too bad we don't have any traffic engineers around to throw in their two cents, but since I did take a traffic engineering course once, I'll give it a whirl.

The cramped quarters of the intersection at bridge make most efforts to stop traffic difficult. The distance is so short that, even if you do detect vehicle speed, you have a very narrow range in which you could operate the system without putting other drivers at risk. You also have to consider where traffic will go once it is stopped. Automated features are great and feasible, but they have to be implemented well before the bridge where there is still an alternate route that the truck can take moving forward.

Here's my idea: I know they put in the laser, but I don't think they did it to a sufficient level. Add blinking lights with height detectors a block before the bridge. At the intersection on the road moving to the bridge, Change the light to a flashing red as traffic approaches. Each car can go in turn after stopping. When the over height truck gets there, solid red with flashing warning signs (and sirens? Maybe not - could be a noise issue - put it to the neighbors to see which is more annoying, the stuck trucks or the siren) directing them to turn. On the road parallel to the bridge, have flashing lights for over height trucks and, as they approach the intersection, have a lighted no right/left hand turn sign with and over height truck label on it to warn them. And also add the hanging "if you hit this" sign (though one that only makes a thumping noise when you run into it) just after the intersection where there is still room to stop.

Make it so visually obnoxious that, if they do manage to not notice, a judge would have no choice but to slap them with reckless endangerment for being asleep while driving through a crowded intersection.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

I like this:

If height too high is detected:
Alarms, signs, lights go on. There should be a "STOP BEFORE HERE" line.
If "STOP HERE LINE" is volated, "truck stopper poles" raise up from ground at entrance.

Good Luck,
Latexman

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

its a bit surprising it takes so little time for things to start moving again in other parts of the world.

After pulling a load of trailers from under railways bridges in Scotland it takes about 2 hours of fannying about to shift the unit and get the trailer out after the Police have done their stuff. Most of that time is the result of various health and safety types having an input. If we were left to do it ourselves we would just disconnect the unit after putting the legs half down on the trailer and letting the air out the tyres. Drop the front and then rip the trailer out backwards with a strop onto the rear axle. Bit more problematic if its skids instead of rollers on the legs. But two round logs and a plank under the skids did the job. Strop onto the pin and pull it round into the right direction. Ram lift the trailer onto the fifth wheel aka some prat forgot to put legs down, connect the suszy's inflate tyres and 100meter accel and brake check and take it back to the yard.


But then its another 12 hours for the bridge to be surveyed and deemed safe for traffic to go under it and trains to go over it.

Personally I would just put a 500 ton tension wire across the front of the bridges 1" lower than the structure and let it cut the top off the lorry. But that's deemed unacceptable in the UK because it would guarantee it would kill anyone in a bus that went under it. They only thing that would defeat it would be a crane jib.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Up-thread we've been advised that warning lamps require "...24 hour watching to see that it functions. ...If the....lamp fails..." ponder

---

'Personally I would just put a 500 ton tension wire across the front of the bridges 1" lower than the structure and let it cut the top off the lorry.'

They use a beam for that purpose, which is why the bridge itself has survived. They've replaced the old bent beam with a new one, adjusted to the new height.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

"It's hard to predict what speed the vehicle will be going as the driver reacts. LOL."

Figuring that out isn't very hard either.

The problem is that it's close to an intersection and high traffic which makes it difficult to single out one vehicle even it you know it's approaching. And of course the large case of "really don"t care".

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

A couple of videos of bridge raising.

Video 1

Video 2

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

What's the buckling strength of scaffolding ?

4 vertical each end, no spreaders on the feet straight onto road surface, 2 diagonal bars and 4 50 ton jacks.... what could go wrong.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

I count 12 jacks. Each jack alongside the midspan supports got its own scaffold. 50 tons is the capacity of the jack, not the load it carries.

So I guessed - the flanges are 1 inch thick; the web is 0.5 inches; the depth of the beam is 24 inches, and the flanges are 8 inches. So each channel is about 8 kips. It's documented as a total span of 92 feet; there are two c-channels per beam, so about 16 kips on 6 jacks. Add about 20% for wood ties and the rails; about 21 kips, or a bit over 3.5 kips per jack.

Even if I was way under and the weight is double, that would be 7 kips; it's 1800 pounds per leg. One supplier offers 10 kips scaffolding with an actual capacity of 40 kips (OSHA 4:1 compliance) and it looks less sturdy than these. Railroads are likely to do this job properly.

In looking at the Wikipedia page I found a safety study was done.

"There have been four deaths and two other injuries in the study area since 1991, compared to only three minor injuries at Gregson." Average, about 1 minor injury per decade at an intersection.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

1800 pounds through a 3" square plate was my main concern and the APN of what it's sitting on.

One corner goes through and your into a nice buckling event.

Personally I would have stuck some metal plate under the legs onto the road and sat the feet on that.

I agree the top looks more than meaty enough. And the vertical scaffolding sufficient. It's the cross bracing and feet support looks a bit suspect in the event of a leg going through the road surface.



Anyway it worked.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

That's 200 psi compression, ~100 psi line shear; maybe 30 psi for a 3 inch layer of macadam.

Where would it go through to? Usually there is a thick layer of crushed and compacted rock for the macadam to sit on.

Like I said, 1700 is if I was off by 100%; I did some deflection and stress calcs on the estimated size and that size is about right. So closer to 100 psi and ~50 psi line shear / 15 psi shear in the paving.

There's only a need for load spreading when there is enough load to worry about.

If you like you might want to estimate the Euler buckling load for the scaffold. Since the loads applied are typically acceptable for a wood 2X4 I expect the steel frame is more than up to the task.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...


charliealphabravo; Thanks for the vids. They gave the bridge the full Monty treatment! Too bad the ad crap on those vids is about the worst I've seen on YouSpood.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

To be honest I have zero clue about imperial units, what is large or small. Engineering wise.

But I have seen the result of a base foot going through tarmac 4 deaths in the middle of Glasgow

Aircraft regularly go through aprons tarmac when people ignore the APN numbers

Anyway dodgy baseplate is alive and kicking in Scotland as well. This is under the Christmas market in Edinburgh.


RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Before they re-packed the rails...



I guess this is the maximum they can do without having to dig up the tracks and totally re configure the base below the ballast. Some of the sleepers look like could do with replacing though....



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

I was stopped at a train crossing on the way in this morning and rather amazed at how much the track flexed up and down with each passing bogie. It had to be moving at least an inch vertically as I was watching it from ~30 feet away. Is that normal?

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Alistair, I'm sure something has gone wrong somewhere. That's what engineers doing the calculations first is for.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Very few scaffolding jobs get an engineer looking at them. People look at the max load of the frame and then throw it up.

UK they now need a license to erect it after the number of collapses that occured. It has reduced the number but not stopped them completely.

My fag packet metric thoughts are 500 tons through 24 plates 250mm square giving 500 tons over 1.5 square meters. Even if it's "only" 250 tons it's still way way over a normal road pressure load 1D. Most aprons couldn't take that.

Stick 1 m2 plates under each foot and your into something sensible.

Your 40 ton lorry is 25 tons onto 12 tyres at .25 m2 each on the trailer.


Now buckling would be of interest in single point of failure not static load. One corner goes through the tarmac what's it going to do?

This case at least the road was closed and it would just drop onto the old supports so no issues from me.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

I think 500 tons is way off though. The previous estimate was about 20 which seems low, but there isn't that much to that bridge. It's only 25m of single track railway supported by a few C section beams. If it was total of 100 tons I would be surprised.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

I was going off one that was removed north of Aberdeen on the Peterhead road. It was less width and 250 tons.

I also have zero clue what the APN of USA roads is, Or if the pavements are the same.

Getting the load pressure down to the legal max of a road vehicle seems sensible to me. Especially when all it requires is the temporary laying down of some plate. Which is pretty standard for mobile cranes. And even then they sometimes kill the surface.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

That pressure is way under what a woman's high heel puts down. Maybe keep them off the apron as well?

I did look for ways that I missed major contributors to weight, but it's clearly pairs of c-channels, one under each rail and rail companies seem unlikely to overspend. A current heavy locomotive, which should weigh a good deal more than any rail car so it should be the upper limit, is about 400 kips. It's weight is split to at least 2 trucks, so the concentrated load is just 200kips and the beam is not a single free span.

No links to that narrower, heavier bridge? This bridge's superstructure isn't as wide as the ties; getting narrower is footpath territory.

Yes - mobile cranes can do damage. Because the heavy ones put down more load than a locomotive. But this isn't a mobile crane or the higher loads that other mobile machinery can put down.


Edit - The 20 kips is per beam. The bridge has 2 beams, so twice that amount for the entire bridge. Of course it is then divided among twice the number of jacks and scaffolds, so back to the original loading.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Ahhh too bad about the ads in the video. I use the AdBlocker extension for Chrome and didn't see them. It works almost all the time.

Edit: This video screenshot shows them working at the train station which is about 600 feet way. I suppose there wasn't much they could do about the grade without it becoming a bigger project. Also I sounds like the job was supposed to be finished in less than a day so the train schedule would not be interrupted.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

High heels do destroy the apron, also air bridges as well and aircraft internal flooring and steps.

Thankfully the amount of pax these days that travel in the high pressure type heels is extremely small and gets smaller by the year. This is pushed by security issues getting through metal detectors with steel shanks in them more than anything else.

Btw the aircraft most likely to sink on aprons and taxi ways at the biz jets with their skinny tyres. The big heavies eg 747 have a collosal tyre foot print and require relatively low APN values.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Those spike heels should be considered a lethal weapon by TSA anyways.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Btw the bridge I was on about could take the Flying Scotsman going over it.

I would still stick spreader plates under the feet. It's not as if it costs anything A rail yard is bound to have some plate kicking about.


I would also put a wire into the stone and attach it to the top. So the frame couldn't go sideways.

Mind you I am a coward when it comes to these things In the house I am building I have 2 eye bolts 4 meters up on the cable ends to strap scaffolding onto. At least you can put some lateral force into jobs and not be scared it's going toppel away with a lardy arse like me 8 meters up trying to put a 30mm hole through 450mm of solid wood.



RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Destroy? Like punch through? British birds are built bigger than I suspected.

The Flying Scotsman was a passenger train, not a locomotive. But maybe the weight is related to the birds? The first run of that line might have been over cast iron bridges, known for their problems with "crystalizing" until the concept of fatigue failure in metals was better understood. The typical response was to just make the structures absurdly heavy. Or was this a stone arch bridge?

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...



It's an engine.

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RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

"The Flying Scotsman was a named passenger train service from London Paddington to Exeter St Davids. It ran from 1849 until 1892, originally over the Great Western Railway (GWR) and then the Bristol and Exeter Railway."

I see that they named an engine for that line.

From the fan page: "By 1924, when it was selected to appear at the British Empire Exhibition in London, the loco had been renumbered 4472 – and been given the name ‘Flying Scotsman’ after the London to Edinburgh rail service which started daily at 10am in 1862."

So while there is support for each side, the service had the name for 62 previous years, the locomotive isn't all that heavy and doesn't apply a near point load. If it takes a massive bridge to hold it, that's a commentary on low strength bridge building materials rather than the size of the engine.

It's quite small. At just over 30,000 lbf tractive effort; is dwarfed by the UP Big Boy series at 135,000 pounds of which 25 were produced, built just 17 years later.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

The bridge was on the Formartine and Buchan Railway which opened in 1865. And was closed to pax with the Beeching cuts in 1960's freight continued on it until the 70's. The metal track was lifted


You can still walk along it and this site has a picture of a typical bridges which were on it that's a single lane one the one removed was about 2.5 times that span. The pic of the bridge I was referring to is not on it. It was speared by a crane with the gib "accidently " left up. Lorrys going up to the Peterhead port with oil equipment had to take a 25 mile detour to get round it. So some 30 odd years ago now an about to retire crane driver hit it doing about 45 mph with 40 tons of crane which shoved it off to the side. And within an hour various oil company's had arranged it to be removed to safety at the side of the road where is sat for years. Every attempt to get it put back on was met with sorry we can't lift it (it was a historically protected bridge so in theory they were meant to put it back the way it was). The old crane driver had his license revoked (he had 3 days left anyway) the 1000 UKP fine was paid by the road hauliers in Aberdeen and he got some 50k UKP retirement present plus 500 quid and a card from Aberdeen police who were as fed up with it as everyone else. . Which some reckon was about 6 months worth of savings of the route now not having a height restriction. I can remember driving under it as a kid and seeing it next to the road. I only got told the story when I was driving the artics in Aberdeen as a holiday job at Uni in my 20's. I don't know for sure if its true but it has a ring to it that it might be mostly true, its definitely something the oil company's would do in that period. The fuel saving wouldn't have been the priority. The cutting the transport time to get a part offshore would have driven it.

https://www.walkhighlands.co.uk/aberdeenshire/form...

The flying scotsman is built for speed. And you can still travel on it. I was very lucky to have had a cab on it.

With a huge amount of effort it can still beat the modern train on the route. The huge effort is the provision of water and coal when required which is extremely often on a speed run. But she is a beauty when going flat out.

RE: Infamous 'can opener' bridge in Durham, NC, is finally being 'fixed'...

Nah, that was a nibble....

Previously it would have rolled the roof back.

Are those trucks commonplace / a standard design?

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