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Somehow I find it surprising how completely the bridge collapsed after the damage. I understand that a container ship collision is serious, but you could imagin

Somehow I find it surprising how completely the bridge collapsed after the damage. I understand that a container ship collision is serious, but you could imagine a scenarios where the bridge slumps or buckles but doesn’t just disintegrate like that. It’s surprising that ships capable of doing this damage were probably regularly driving past it, and its safety as a thoroughfare depended entirely on those collisions not happening. Does anyone know if modern construction standards would require more stability after a ship collision, or is this still how we build bridges?

pdntspa 3y ago
That bridge looks like its almost entirely made of just trusses. It's hard to imagine how one might expect it not to collapse when everything holding it together is so thin.
EasyMark 3y ago
If you watch it in slow motion and how it breaks apart, you won't really find it surprising how things snap and bend considering how big the container ship is compared to the bridge. It makes a lot of sense.
makach 3y ago
Modern bridges are required to endure a collision. This bridge might be very old and not sufficiently maintained against current requirements.
- Reason077 3y ago
  It opened in 1977. So, oldish, but not that old. Plenty of far older bridges around than that. https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_(Baltimore) https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_(Balt...
  - loeg 3y ago
    Notably predating the 1980 collapse of the Sunshine Skyway after a ship hit.
    - Reason077 3y ago
      Neat how they made what was left of the old bridge into a giant fishing pier!
- hgomersall 3y ago
  I'm not sure how many brand new bridges would stay up after having one of the piers on the main span removed.
  - rob74 3y ago
    The trick is to make sure the piers are not removed. For example, the new Tampa Bay Sunshine Skyway Bridge (rebuilt after a similar disaster): > In addition to a wider shipping lane, the channel would be marked by a 1⁄4 mi (400 m)-long series of large concrete barriers, and the support piers would be protected by massive concrete "dolphins". https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#/media/File:Skyway_Bridge_old_and_new.jpg https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#/media/...
    - gregors 3y ago
      Good view of them on Google maps https://www.google.com/maps/place/Sunshine+Skyway+Bridge/@27.6223368,-82.6586101,954m/data=!3m1!1e3!4m6!3m5!1s0x88c31db3105de9a5:0x53e7724a2432b4a6!8m2!3d27.6207079!4d-82.6558418!16zL20vMDJ3dzdo https://www.google.com/maps/place/Sunshine+Skyway+Bridge/@27...
- guenthert 3y ago
  Collision with what? I'm pretty sure that with a sufficiently massive ship sailing fast enough, one could take down any bridge. Hence I'd think there are limits which ship may approach at a given speed. Was one of those limits perhaps exceeded?
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- boringg 3y ago
  Collision means nothing without magnitude of force. A glancing blow is completely different from a direct hit. And the amount of Newtons behind the blow completely changes the outcomes. A small ship versus a loaded container ship is a completely different force. I doubt many bridges would take a full speed, fully loaded container ship directly to one of their supports and survive it. Certainly the most celebrated bridges have a better chance of surviving but I doubt any second tier, lower traveled routes would.
  - bmitc 3y ago
    Apparently this container ship was only half loaded to capacity. And it seems likely that a container ship would hit it given the vicinity of such container ships. I'm generally confused on this matter.
    - boringg 3y ago
      It hit the support completely dead on and stopped. All of that momentum and force went directly into the bridge. The pulse from that impact would have been enormous. Why would you anticipate that a container ship would have to hit the bridge? What about the flip side to that... How many bridges have never been hit by a container ship or alternatively how many times have an almost fully loaded container ship come to a dead stop after hitting a bridge?
      - bmitc 3y ago
        According to a quick search and reporting due to this event, apparently a quick number is a few dozen full collapses in the past 55 years, which doesn't seem to account for impacts and collisions that didn't result in full collapses. So that seems like a lot of bridges indeed, along with a lot of deaths and economic impact. The reason why I would anticipate a container ship hitting that bridge is because of the video we've all seen. It's a huge ship that is going the slowest it can while still retaining control over the vehicle, unattended, through a tight spot, close to a bridge with zero protection from ship collisions, and all with a ship design that is apparently (according to other comments) effectively impossible to correctly maintain and keep running at all times. So I think the better question is, why wouldn't you anticipate a collision?
_giorgio_ 3y ago
The problem is the static scheme of the bridge. Most modern bridges are hyperstatic: if you remove one support, it still stands. Or at least isostatic: you remove one support or one span, and nothing happens to the nearest ones. This bridge was ill conceived: you remove one support or span, and it brings down everything like a chain that pulls down everything it's linked to. It's bad because the "engineer" just wanted to show off.
- 4gotunameagain 3y ago
  You cannot put the entire weight of the 70's safety culture to an engineer "showing off" I bet there was a much more complex and nuanced analysis which included crossing ship dimensions, budget, time to completion, available technology, composition of the local seabed etc.. Designing a bridge is proper engineering and not that easy.
  - baq 3y ago
    > Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands. ...in other words.
  - _giorgio_ 3y ago
    Believe me, an engineering student that sees that, immediately understands the problems after taking the first science of construction lessons. You do need need the truss at all. If the truss fails (in any of the three spans), it brings down two adjacents spans. It's just a show off.
    - bigbillheck 3y ago
      There's been at least 50 years, probably more like 60 or 70, of advances in the art (much less pedagogy) that those students have and the bridge engineer did not.
  - Tanoc 3y ago
    The '70s were also a transitional period in bridge design where truss bridges were being phased out in favour of newer types of hybrid suspension bridge. Many of the iron and steel bridges of the 1890s through the 1970s were later replaced with suspension bridges or arch span bridges because they used less material and could be architecturally adapted to the area better. So some truss bridges were made as much for appearance as function in order to compete with the futuristic hybrid suspension bridges like the 1967 Ponte Morandi or the 1987 replacement Sunshine Skyway.
mkl 3y ago
Not all bridges are this vulnerable to a single impact. This one, opened 12 years earlier, has a different style and mostly survived a cargo ship impact: https://en.wikipedia.org/wiki/Tasman_Bridge_disaster https://en.wikipedia.org/wiki/Tasman_Bridge_disaster
- somat 3y ago
  I would say the damage is about the same, The ship knocked down a pier and all spans connected to the pier went down. The difference is, on the baltimore bridge is that the spans are a lot longer. But all other spans(the ones nearly out of frame) are still standing.
  - mkl 3y ago
    Parts of the Francis Scott Key Bridge not connected to the hit pylon went down too. The beam structure above the road that supports the whole thing collapsed and took down other spans.
    - somat 3y ago
      Yes the entire truss section dropped. However the bridge is quite a few times longer than it's trussed section. and none of those spans dropped.
    - xeonmc 3y ago
      Maybe it's the extra momentum that took it over the edge, which if it were built in the 70s probably were designed with static loading in mind without the benefit of dynamical simulation?
    - whizzter 3y ago
      And that structure probably existed because the bridge has fewer longer spans, probably since the seabed below the bridge is deeper (and needs to be deeper to support container ships passing below). The Öresundsbron (connecting Sweden and Denmark) features both short segments but also with an overhand section in the middle for larger ships to pass through. (1) The great belt bridge (inside Denmark) is slightly higher but has the same kind of profile, one of the largest cruise ships barely making it under it is shown passing in the video below (2). I think the simple truth is that we're vulnerable to these kinds of accidents unless we build far far sturdier bridges, but at these scales to allow passage of ships of these sizes the cost would just make many bridge projects prohibitably expensive. 1: https://www.norden.org/sites/default/files/styles/content_size_800/public/2021-03/%C3%98resund.jpg?h=0583ede9&itok=vfdhJoKL https://www.norden.org/sites/default/files/styles/content_si... 2: https://www.youtube.com/watch?app=desktop&v=j1Cs0C8LkeU https://www.youtube.com/watch?app=desktop&v=j1Cs0C8LkeU
irjustin 3y ago
This situation is terrible, but to your specific question: Anyone can build a bridge, but it takes an engineer to barely make it stand.
- jack_riminton 3y ago
  I like this quote. We have a medieval bridge near to our house (1000 years old perhaps), it's incredibly solidly built, but could you call it well-engineered? It's a subtle distinction that I don't think many in the digital realm quite grasp either i.e. far too many over-engineered technical solutions for features and products that aren't even desired
  - lukan 3y ago
    "but could you call it well-engineered" If it is still standing after 1000 years, I would say yes. You cannot build a bridge out of stones with bad engineering - it would collapse under its own weight. edit: does "well engineered" now means over engineered to some?
    - jack_riminton 3y ago
      "If it is still standing after 1000 years, I would say yes" but what if they included far more material in areas where it wasn't needed, skimped on other areas and it fell down tomorrow? It's almost a philosophical question, and it's true that the bridge builders happened across a solid design by accident. But I think the true definition of engineering has to encompass a level of efficiency through design, calculation and rationalization. In other words, echoing what the original commenter said, including only what is barely necessary.
      - lukan 3y ago
        "and it's true that the bridge builders happened across a solid design by accident" Or by experience and learning from other sucessful bridges? Stone bridges were not new in the year 1000. There is a roman bridge that was allmost completely surviving all this time, till it was blown up in WW2: https://en.m.wikipedia.org/wiki/Ponte_Pietra_(Verona) https://en.m.wikipedia.org/wiki/Ponte_Pietra_(Verona) If they wanted a cheap solution, they would have used wood. But wood does not last a 1000 years. Personally I salute anyone, who can build something that lasts that long. "including only what is barely necessary." And "barely necessary" in solid engineering includes lots of safety margins. Not barely standing. And yes, that includes not using more than you need, because the more material you use, the heavier your bridge is -> the greater are the forces on the structure itself even with no one passing over it. There are some fun games out there on various plattforms, google "bridge builder" Not a scientific simulation of course, but they do show the concept.
somat 3y ago
I would guess none. No bridge span could survive complete loss of it's supporting abutment. Some bridges are engineered to survive partial loss. For example if the left side goes the right side will hold it up. But from the video the ship looks like it took out the entire supporting structure.
gnfargbl 3y ago
Why would slumping or buckling but not-quite-collapsing be a functionally better outcome than complete failure? In both cases, the sheer size of the physical changes is going to lead to forces that humans won't survive, so there's no benefit there. In both cases, the bridge is going to have to be completely demolished before rebuilding, so there's no benefit there. A bridge that could stand the loss of a single support pier without any significant collapse would obviously be preferable -- but that's a big ask. I'm not a structural engineer, but I am aware of scaling laws [1] and it feels to me that those scaling laws are going to mean that increasing the margin of safety by x is going to increase costs by x^n. For a project like this one, where cost was apparently the deciding factor over a tunnel, that matters. [1] https://galileo.phys.virginia.edu/classes/609.ral5q.fall04/LecturePDF/L14-GALILEOSCALING.pdf https://galileo.phys.virginia.edu/classes/609.ral5q.fall04/L...
- Dalewyn 3y ago
  >Why would slumping or buckling but not-quite-collapsing be a functionally better outcome than complete failure? Well for starters, there's a better chance of less (or ideally no) people forced to get their feet wet and go missing or die from drowning or hypothermia.
  - gnfargbl 3y ago
    The specific point I'm making (in the sentence following the one you quoted) is that no, there is not a better chance of those things. If a bridge of this size is going to fail in any significant way, it is going to lead to loss of life. The broader point is that attempts to blame the bridge designers here are misplaced. It really isn't reasonable to have hoped that they could design a structure that could cope with this kind of failure, within the cost constraints that they had. And cost constraints were a real thing for the designers of this particular bridge.
archi42 3y ago
You could try to avoid collisions with barriers, or make the bridge fail differently (only a few spans), or make it tolerant to a single support failing. But you need a pretty beefy steel beam to survive a direct hit by... Uh... 200,000t(??) traveling even at a slow jogging pace. (And then it transfers the energy into the rest of the bridge, which will very much not like it). I guess we can be happy failure like this is rare, and that the bridge was not busy: reports indicate 13 cars, and about 7 persons still missing. This could be so much worse. The best way to think about measures is after we know the full chain of events that have lead to this.
- bagels 3y ago
  Some other bridges have barriers around, but not connecting to the pylons.
  - Kye 3y ago
    Those are great for little boats like one of those superyachts. They become dominoes that hit before a boat like this: https://www.vesselfinder.com/?imo=9697428 https://www.vesselfinder.com/?imo=9697428
    - archi42 3y ago
      Absolutely. 116851 long tons deadweight, which the Google info box says includes everything (busy now, so can't check in detail). That's 120,000,000 kg, so a little bit less than I guessed. Now looking at 10km/h or 6.2mi/h or 2.78m/s, that's enough to come up with a big E for E = 1/2 * m * v². The momentum p = m * v is also rather unpleasant. If the momentum was suddenly transferred into my 2,000 kg car (e.g. if the ship hit my car), I could do my work trip in about 1s, though that's only a few times times faster than the ISS (which travels at 7660 m/s). [I'm very busy, so hopefully I didn't forget/add a few 0s by accident. Anyone feel free to correct me if I did.]
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onetimeuse92304 3y ago
Most bridges nowadays (say last century) depend on a careful balance of forces that are transferred through a chain of members in tension and compression. When any piece in the chain of those forces breaks, the entire structure loses ability to transfer forces and breaks. This arrangement is what allows us to build these structures in the first place. There is careful calculations of forces and risks and allowance for margin for error and unexpected events. But, unfortunately, in many cases those do not include ramming things with a large container ship...
- rkagerer 3y ago
  Many homes also incorporate lightweight trusses that can fail in a similar fashion. They pose a unique risk for firefighters, which is why New York went so far as to require warnings be posted outside such structures: https://www.finehomebuilding.com/2015/01/28/new-york-now-requires-truss-warning-on-buildings https://www.finehomebuilding.com/2015/01/28/new-york-now-req...
- armchairdweller 3y ago
  Thanks! So why are huge—ass container ships allowed to navigate underneath fragile public bridges with single points of failure? The not unlikely worst case is that the ship is out of control for some reason…
  - oliviabenson 3y ago
    We notice these type of accidents because they’re so rare. 5k+ people die each year because of large trucks on the road, by comparison, boats and bridges are very safe — that’s why it’s allowed.
    - 3seashells 3y ago
      [dead]
  - bombcar 3y ago
    Because bridges over harbors are quite common an incidents like this are rare.
loeg 3y ago
Check out Brick Immortar (it’s a pun) on YouTube for some in depth videos on past container ship collisions with bridges and how newer bridges are engineered.
- rpeden 3y ago
  Here's the one about the Sunshine Skyway Bridge collapse in Tampa Bay: https://youtu.be/3htwtaJI2nM?si=7SKMY2qxQEQpaf-O https://youtu.be/3htwtaJI2nM?si=7SKMY2qxQEQpaf-O It's pretty similar to this one.
dist-epoch 3y ago
People love bridges which look sleek, thin and like air. They are also cheaper (less materials). But this means there is no redundancy left.
cool_dude85 3y ago
The Mathews Bridge in Jacksonville was clipped by a container ship a few years back and did not collapse. Despite being almost 75 years old, they fixed it up and it opened back up after a year or two. The difference is that the boat did not hit a pylon.
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plastic3169 3y ago
There is this often in HN featured article about bridge engineer analysing bridge collapses in film [1]. It’s about suspension bridges though but the takeaway for me was that when they go they go completely. [1] https://hackaday.com/2015/11/18/suspension-bridges-of-disbelief/ https://hackaday.com/2015/11/18/suspension-bridges-of-disbel...
dathinab 3y ago
At least in the links with the video now you can see that the container ship directly hits one of the two main (and in the central area only) pillars completely collapsing it. No matter(1) the engineering there is no pretty much way to not lose the whole large middle area and left area leading to the destroyed pillar in that situation. Such a collapse crates so much force (tension vibrations etc.) so that the collapse of the section right of the right pillar is not unreasonable. The only question is if the impact should have made the pillar collapse. But a loaded container ship is ... absurdly massive I mean they are like multiple high raise building (but not sky scrapers) standing squished together side by side. So the force it can apply is huge and if cargo moving in it there will be force applied to whatever it crashes into even after the initial impact. And looking at the waves caused by impact with the base it was at least 8m high I think (depending on the container ship). So that wasn't a "slow moving" impact. And even slow moving impacts with container ships can tear apart a solid jetty. So while the US has issues with infrastructure maintenance idk. if anything but building a many pillar bridge would have made any difference. And building a many pillar bridge might not be very viable depending on the under water landscape and water use under the main area. EDIT: Looking at pictures with daylight where you can try to estimate the high of the ship using containers I would say the waves where handwavingly 4 containers high so ~9.5m and it also looks like the ship might have embedded half of the pillars fundament into/under itself (but it's a bit hard to tell to the angle of the picture). I think if that's the case probably the huge majority of bridge pillars of past and presence would have collapsed.
- JohnBooty 3y ago
  It certainly does not seem reasonable to design a bridge pillar to withstand a direct impact from a massive cargo ship. But I guess I thought that maybe there was... typically some kind of earthen buffer around the pillar to prevent such an impact? That's probably impractical too, I guess. I guess I just didn't realize ~$1bn bridges were one fluky ship accident away from total collapse at any given time. I think maybe I prefer my previous state of ignorance, to be quite honest....
  - hgomersall 3y ago
tyingq 3y ago
I did hear one expert on the news say that a better, low-tech defense some bridges have is sacrificial piers in front of the actual ones. I don't know if this bridge had none, or if they didn't get the job done.
bluedino 3y ago
The Bay Bridge in SF has been hit by numerous ships (as large as tankers)
- sf_rob 3y ago
  The 2007 Cosco Busan incident appears to be a glancing blow. I can't find any information suggesting an analogous impact at any point.
bluedino 3y ago
> It’s surprising that ships capable of doing this damage were probably regularly driving past it, and its safety as a thoroughfare depended entirely on those collisions not happening. There are cities with skyscrapers near airports, which depend on the airplanes not hitting the skyscrapers.
chasd00 3y ago
I don’t drive boats or around water much but I’ve seen “bumpers” on bridge pylons before that make a collision more of a glancing blow and guide the boat to the side. I guess there wasn’t any installed on this bridge? Also, someone on Imgur pointed out that when this bridge was built boats that large weren’t a risk. That may or may not be true but sounds plausible.
- fl7305 3y ago
  > when this bridge was built boats that large weren’t a risk Doesn't sound plausible to me. Very large Panamax ships were used in the 1970's when the bridge was built.
  - 1letterunixname 3y ago
    Sorry, but you're very wrong. A civil engineer on Sky News even raised this issue. https://www.container-transportation.com/worlds-largest-container-ship.html https://www.container-transportation.com/worlds-largest-cont...
    - fl7305 3y ago
      Panamax specifications (320 m length, 32 m width) have been in effect since the opening of the canal in 1914. Some ships were already larger than that back then. The Titanic was about that size. The ship that knocked down the bridge could weigh ("DWT") up to 115 000 tons. Some ships from the 1960s and 1970s: Universe Ireland: Launched in 1968, it had a DWT of over 300 000 tons. Esso Atlantic (1977): DWT of over 500 000 tons. But these were tankers. You're right that container ships were not as big back then. One of the larger container ships when the bridge was built in 1977 was MV Hamburg Express. It was 280 meters long, 32 meters wide, and had a DWT of 50 000 tons. Do you really think a 280 meter long ship weighing 50 000 tons would not have knocked down the bridge in exactly the same way? https://de.wikipedia.org/wiki/Hamburg-Express-Klasse_(1972) https://de.wikipedia.org/wiki/Hamburg-Express-Klasse_(1972)
- hnburnsy 3y ago
  There were tiny bumpers, two for each pylon, one on each side, but looks like they were place too far out, you can see them here... https://i.pinimg.com/736x/1c/6e/f8/1c6ef8db981c77b1bd780982742d5e65--spangled-banner-star-spangled.jpg https://i.pinimg.com/736x/1c/6e/f8/1c6ef8db981c77b1bd7809827... Ironically there are power lines running in parallel that have much more substantial protection, here you can see the powerline protection and the tiny bumpers... https://patabook.com/news/wp-content/uploads/2024/03/cbsn-fusion-baltimore-key-bridge-collapse-details-rescue-efforts-reactions-thumbnail-2787613-640x360.jpg https://patabook.com/news/wp-content/uploads/2024/03/cbsn-fu...
Lance_ET_Compte 3y ago
In 2013, a tanker ship hit the Bay Bridge (Oakland <--> SF) but didn't do much damage. In 2007, another tanker (Cosco Busan) hit the same bridge dumping oil into the bay: https://www.youtube.com/watch?v=upfjxfl2nRM https://www.youtube.com/watch?v=upfjxfl2nRM. We have a new bridge there now because that one was also damaged in the Loma Prieta earthquake. When the Golden Gate needs replacement, the Marin NIMBY's that didn't extend BART to the north bay are going to be sad (more likely, their children will be).
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ak_111 3y ago
This brings back to memory 911 conspiracy theories. Many revolved around the unlikelihood that a building would collapse the way the towers collapsed just due to knocking out a few floors at the top. But the truth is all these mega structures are quite fragile and can instantly collapse in unintuitive ways.
G0dchi1d 3y ago
The ongoing construction work likely creaty some type of structural integrity issue...
patrickwalton 3y ago
In many structures, catastrophic failures are far more likely than graceful failures.
foxhop 3y ago
these ships have to be boarded by special port captians to make this maneuver.
CydeWeys 3y ago
One factor that a lot of people in this discussion are missing is that buildings are primarily built to resist vertical forces, because gravity is by far the largest force any building (or bridge) ever experiences. Having a large force strike perpendicular to gravity is just not something it's designed for at all. All it ever has to handle in the form of force from that direction is wind, and that's absolutely nothing compared to a fully laden container ship hitting it.
doer1984 3y ago
Ironically, simply bulking up the ground around the piers would have had the ship run aground; at 8 knots the ship would have slowed to a stop within several yards, and suffered minor damage, maybe would have required being tugged back into clear waters. Running aground puts the majority of impact into a downward force absorbed by the earth. It's hard to build a bridge pier that will withstand 200,000 tons of direct impact, no matter how slowly that's moving.
- adrianmonk 3y ago
  That's what makes sense to me. Ships are designed to minimize drag going through the water. But the friction of the entire hull scraping across the bottom should be MUCH larger and thus able to exert lots more stopping force. Also, if the ground is sloped, it will act like a ramp, lifting the ship out of the water. The loss of buoyancy means its weight will push downward on the ground below it. An increased normal force means more friction, thus more stopping ability.
- fl7305 3y ago
  > simply bulking up the ground around the piers That is exactly what they did around the pylons of the large Öresundsbridge between Denmark and Sweden.
doer1984 3y ago
Simply bulking up the ground around the piers with loose fill or monolithic concrete would have had the ship run aground; at 9mph (the recorded impact speed) the ship would have slowed to a stop within several yards, and suffered minor damage, maybe would have required being tugged back into clear waters. Running aground puts the majority of impact into a downward force absorbed by the earth. It's hard to build a bridge pier that will withstand 200,000 tons of direct impact, no matter how slowly that's moving.
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hwh47 3y ago
separate but pertinent question: what was the mv dali's air draft? (FSK bridge's clearance is 185'/56m) was the container ship going to fit under the bridge, i.e., perhaps the incident was an aborted attempt to crossing under the bridge?
- lolc 3y ago
  I'd assume the procedure of how the ship will enter and leave was clear to all involved before it even got close to Baltimore.
hwh47 3y ago
separate but pertinent question: what was the mv dali's air draft? (FSK bridge's clearance is 185'/56m) ...perhaps the incident was an aborted attempt to crossing under the bridge?
doer1984 3y ago
Anyone know about backup steering power on these vessels? I know they typically keep emergency generators, but does this provide adequate steering power?
frankfrank13 3y ago
Someone hasn't played enough polybridge
snarf21 3y ago
Is there a reason we don't force ships above a certain side to always approach a bridge like this perpendicular in the main channels? Seems like a trivial thing to implement immediately and makes this never happen again.

pdntspa 3y ago

That bridge looks like its almost entirely made of just trusses. It's hard to imagine how one might expect it not to collapse when everything holding it together is so thin.

EasyMark 3y ago

If you watch it in slow motion and how it breaks apart, you won't really find it surprising how things snap and bend considering how big the container ship is compared to the bridge. It makes a lot of sense.

makach 3y ago

Modern bridges are required to endure a collision. This bridge might be very old and not sufficiently maintained against current requirements.

Reason077 3y ago
It opened in 1977. So, oldish, but not that old. Plenty of far older bridges around than that. https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_(Baltimore) https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_(Balt...
- loeg 3y ago
  Notably predating the 1980 collapse of the Sunshine Skyway after a ship hit.
  - Reason077 3y ago
    Neat how they made what was left of the old bridge into a giant fishing pier!
hgomersall 3y ago
I'm not sure how many brand new bridges would stay up after having one of the piers on the main span removed.
- rob74 3y ago
  The trick is to make sure the piers are not removed. For example, the new Tampa Bay Sunshine Skyway Bridge (rebuilt after a similar disaster): > In addition to a wider shipping lane, the channel would be marked by a 1⁄4 mi (400 m)-long series of large concrete barriers, and the support piers would be protected by massive concrete "dolphins". https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#/media/File:Skyway_Bridge_old_and_new.jpg https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#/media/...
  - gregors 3y ago
    Good view of them on Google maps https://www.google.com/maps/place/Sunshine+Skyway+Bridge/@27.6223368,-82.6586101,954m/data=!3m1!1e3!4m6!3m5!1s0x88c31db3105de9a5:0x53e7724a2432b4a6!8m2!3d27.6207079!4d-82.6558418!16zL20vMDJ3dzdo https://www.google.com/maps/place/Sunshine+Skyway+Bridge/@27...
guenthert 3y ago
Collision with what? I'm pretty sure that with a sufficiently massive ship sailing fast enough, one could take down any bridge. Hence I'd think there are limits which ship may approach at a given speed. Was one of those limits perhaps exceeded?
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boringg 3y ago
Collision means nothing without magnitude of force. A glancing blow is completely different from a direct hit. And the amount of Newtons behind the blow completely changes the outcomes. A small ship versus a loaded container ship is a completely different force. I doubt many bridges would take a full speed, fully loaded container ship directly to one of their supports and survive it. Certainly the most celebrated bridges have a better chance of surviving but I doubt any second tier, lower traveled routes would.
- bmitc 3y ago
  Apparently this container ship was only half loaded to capacity. And it seems likely that a container ship would hit it given the vicinity of such container ships. I'm generally confused on this matter.
  - boringg 3y ago
    It hit the support completely dead on and stopped. All of that momentum and force went directly into the bridge. The pulse from that impact would have been enormous. Why would you anticipate that a container ship would have to hit the bridge? What about the flip side to that... How many bridges have never been hit by a container ship or alternatively how many times have an almost fully loaded container ship come to a dead stop after hitting a bridge?
    - bmitc 3y ago
      According to a quick search and reporting due to this event, apparently a quick number is a few dozen full collapses in the past 55 years, which doesn't seem to account for impacts and collisions that didn't result in full collapses. So that seems like a lot of bridges indeed, along with a lot of deaths and economic impact. The reason why I would anticipate a container ship hitting that bridge is because of the video we've all seen. It's a huge ship that is going the slowest it can while still retaining control over the vehicle, unattended, through a tight spot, close to a bridge with zero protection from ship collisions, and all with a ship design that is apparently (according to other comments) effectively impossible to correctly maintain and keep running at all times. So I think the better question is, why wouldn't you anticipate a collision?

_giorgio_ 3y ago

The problem is the static scheme of the bridge. Most modern bridges are hyperstatic: if you remove one support, it still stands. Or at least isostatic: you remove one support or one span, and nothing happens to the nearest ones. This bridge was ill conceived: you remove one support or span, and it brings down everything like a chain that pulls down everything it's linked to. It's bad because the "engineer" just wanted to show off.

4gotunameagain 3y ago
You cannot put the entire weight of the 70's safety culture to an engineer "showing off" I bet there was a much more complex and nuanced analysis which included crossing ship dimensions, budget, time to completion, available technology, composition of the local seabed etc.. Designing a bridge is proper engineering and not that easy.
- baq 3y ago
  > Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands. ...in other words.
- _giorgio_ 3y ago
  Believe me, an engineering student that sees that, immediately understands the problems after taking the first science of construction lessons. You do need need the truss at all. If the truss fails (in any of the three spans), it brings down two adjacents spans. It's just a show off.
  - bigbillheck 3y ago
    There's been at least 50 years, probably more like 60 or 70, of advances in the art (much less pedagogy) that those students have and the bridge engineer did not.
- Tanoc 3y ago
  The '70s were also a transitional period in bridge design where truss bridges were being phased out in favour of newer types of hybrid suspension bridge. Many of the iron and steel bridges of the 1890s through the 1970s were later replaced with suspension bridges or arch span bridges because they used less material and could be architecturally adapted to the area better. So some truss bridges were made as much for appearance as function in order to compete with the futuristic hybrid suspension bridges like the 1967 Ponte Morandi or the 1987 replacement Sunshine Skyway.

mkl 3y ago

Not all bridges are this vulnerable to a single impact. This one, opened 12 years earlier, has a different style and mostly survived a cargo ship impact: https://en.wikipedia.org/wiki/Tasman_Bridge_disaster https://en.wikipedia.org/wiki/Tasman_Bridge_disaster

somat 3y ago
I would say the damage is about the same, The ship knocked down a pier and all spans connected to the pier went down. The difference is, on the baltimore bridge is that the spans are a lot longer. But all other spans(the ones nearly out of frame) are still standing.
- mkl 3y ago
  Parts of the Francis Scott Key Bridge not connected to the hit pylon went down too. The beam structure above the road that supports the whole thing collapsed and took down other spans.
  - somat 3y ago
    Yes the entire truss section dropped. However the bridge is quite a few times longer than it's trussed section. and none of those spans dropped.
  - xeonmc 3y ago
    Maybe it's the extra momentum that took it over the edge, which if it were built in the 70s probably were designed with static loading in mind without the benefit of dynamical simulation?
  - whizzter 3y ago
    And that structure probably existed because the bridge has fewer longer spans, probably since the seabed below the bridge is deeper (and needs to be deeper to support container ships passing below). The Öresundsbron (connecting Sweden and Denmark) features both short segments but also with an overhand section in the middle for larger ships to pass through. (1) The great belt bridge (inside Denmark) is slightly higher but has the same kind of profile, one of the largest cruise ships barely making it under it is shown passing in the video below (2). I think the simple truth is that we're vulnerable to these kinds of accidents unless we build far far sturdier bridges, but at these scales to allow passage of ships of these sizes the cost would just make many bridge projects prohibitably expensive. 1: https://www.norden.org/sites/default/files/styles/content_size_800/public/2021-03/%C3%98resund.jpg?h=0583ede9&itok=vfdhJoKL https://www.norden.org/sites/default/files/styles/content_si... 2: https://www.youtube.com/watch?app=desktop&v=j1Cs0C8LkeU https://www.youtube.com/watch?app=desktop&v=j1Cs0C8LkeU

irjustin 3y ago

This situation is terrible, but to your specific question: Anyone can build a bridge, but it takes an engineer to barely make it stand.

jack_riminton 3y ago
I like this quote. We have a medieval bridge near to our house (1000 years old perhaps), it's incredibly solidly built, but could you call it well-engineered? It's a subtle distinction that I don't think many in the digital realm quite grasp either i.e. far too many over-engineered technical solutions for features and products that aren't even desired
- lukan 3y ago
  "but could you call it well-engineered" If it is still standing after 1000 years, I would say yes. You cannot build a bridge out of stones with bad engineering - it would collapse under its own weight. edit: does "well engineered" now means over engineered to some?
  - jack_riminton 3y ago
    "If it is still standing after 1000 years, I would say yes" but what if they included far more material in areas where it wasn't needed, skimped on other areas and it fell down tomorrow? It's almost a philosophical question, and it's true that the bridge builders happened across a solid design by accident. But I think the true definition of engineering has to encompass a level of efficiency through design, calculation and rationalization. In other words, echoing what the original commenter said, including only what is barely necessary.
    - lukan 3y ago
      "and it's true that the bridge builders happened across a solid design by accident" Or by experience and learning from other sucessful bridges? Stone bridges were not new in the year 1000. There is a roman bridge that was allmost completely surviving all this time, till it was blown up in WW2: https://en.m.wikipedia.org/wiki/Ponte_Pietra_(Verona) https://en.m.wikipedia.org/wiki/Ponte_Pietra_(Verona) If they wanted a cheap solution, they would have used wood. But wood does not last a 1000 years. Personally I salute anyone, who can build something that lasts that long. "including only what is barely necessary." And "barely necessary" in solid engineering includes lots of safety margins. Not barely standing. And yes, that includes not using more than you need, because the more material you use, the heavier your bridge is -> the greater are the forces on the structure itself even with no one passing over it. There are some fun games out there on various plattforms, google "bridge builder" Not a scientific simulation of course, but they do show the concept.

somat 3y ago

I would guess none. No bridge span could survive complete loss of it's supporting abutment. Some bridges are engineered to survive partial loss. For example if the left side goes the right side will hold it up. But from the video the ship looks like it took out the entire supporting structure.

gnfargbl 3y ago

Why would slumping or buckling but not-quite-collapsing be a functionally better outcome than complete failure? In both cases, the sheer size of the physical changes is going to lead to forces that humans won't survive, so there's no benefit there. In both cases, the bridge is going to have to be completely demolished before rebuilding, so there's no benefit there. A bridge that could stand the loss of a single support pier without any significant collapse would obviously be preferable -- but that's a big ask. I'm not a structural engineer, but I am aware of scaling laws [1] and it feels to me that those scaling laws are going to mean that increasing the margin of safety by x is going to increase costs by x^n. For a project like this one, where cost was apparently the deciding factor over a tunnel, that matters. [1] https://galileo.phys.virginia.edu/classes/609.ral5q.fall04/LecturePDF/L14-GALILEOSCALING.pdf https://galileo.phys.virginia.edu/classes/609.ral5q.fall04/L...

Dalewyn 3y ago
>Why would slumping or buckling but not-quite-collapsing be a functionally better outcome than complete failure? Well for starters, there's a better chance of less (or ideally no) people forced to get their feet wet and go missing or die from drowning or hypothermia.
- gnfargbl 3y ago
  The specific point I'm making (in the sentence following the one you quoted) is that no, there is not a better chance of those things. If a bridge of this size is going to fail in any significant way, it is going to lead to loss of life. The broader point is that attempts to blame the bridge designers here are misplaced. It really isn't reasonable to have hoped that they could design a structure that could cope with this kind of failure, within the cost constraints that they had. And cost constraints were a real thing for the designers of this particular bridge.

archi42 3y ago

You could try to avoid collisions with barriers, or make the bridge fail differently (only a few spans), or make it tolerant to a single support failing. But you need a pretty beefy steel beam to survive a direct hit by... Uh... 200,000t(??) traveling even at a slow jogging pace. (And then it transfers the energy into the rest of the bridge, which will very much not like it). I guess we can be happy failure like this is rare, and that the bridge was not busy: reports indicate 13 cars, and about 7 persons still missing. This could be so much worse. The best way to think about measures is after we know the full chain of events that have lead to this.

bagels 3y ago
Some other bridges have barriers around, but not connecting to the pylons.
- Kye 3y ago
  Those are great for little boats like one of those superyachts. They become dominoes that hit before a boat like this: https://www.vesselfinder.com/?imo=9697428 https://www.vesselfinder.com/?imo=9697428
  - archi42 3y ago
    Absolutely. 116851 long tons deadweight, which the Google info box says includes everything (busy now, so can't check in detail). That's 120,000,000 kg, so a little bit less than I guessed. Now looking at 10km/h or 6.2mi/h or 2.78m/s, that's enough to come up with a big E for E = 1/2 * m * v². The momentum p = m * v is also rather unpleasant. If the momentum was suddenly transferred into my 2,000 kg car (e.g. if the ship hit my car), I could do my work trip in about 1s, though that's only a few times times faster than the ISS (which travels at 7660 m/s). [I'm very busy, so hopefully I didn't forget/add a few 0s by accident. Anyone feel free to correct me if I did.]
    - deleted 3y ago
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onetimeuse92304 3y ago

Most bridges nowadays (say last century) depend on a careful balance of forces that are transferred through a chain of members in tension and compression. When any piece in the chain of those forces breaks, the entire structure loses ability to transfer forces and breaks. This arrangement is what allows us to build these structures in the first place. There is careful calculations of forces and risks and allowance for margin for error and unexpected events. But, unfortunately, in many cases those do not include ramming things with a large container ship...

rkagerer 3y ago
Many homes also incorporate lightweight trusses that can fail in a similar fashion. They pose a unique risk for firefighters, which is why New York went so far as to require warnings be posted outside such structures: https://www.finehomebuilding.com/2015/01/28/new-york-now-requires-truss-warning-on-buildings https://www.finehomebuilding.com/2015/01/28/new-york-now-req...
armchairdweller 3y ago
Thanks! So why are huge—ass container ships allowed to navigate underneath fragile public bridges with single points of failure? The not unlikely worst case is that the ship is out of control for some reason…
- oliviabenson 3y ago
  We notice these type of accidents because they’re so rare. 5k+ people die each year because of large trucks on the road, by comparison, boats and bridges are very safe — that’s why it’s allowed.
  - 3seashells 3y ago
    [dead]
- bombcar 3y ago
  Because bridges over harbors are quite common an incidents like this are rare.

loeg 3y ago

Check out Brick Immortar (it’s a pun) on YouTube for some in depth videos on past container ship collisions with bridges and how newer bridges are engineered.

rpeden 3y ago
Here's the one about the Sunshine Skyway Bridge collapse in Tampa Bay: https://youtu.be/3htwtaJI2nM?si=7SKMY2qxQEQpaf-O https://youtu.be/3htwtaJI2nM?si=7SKMY2qxQEQpaf-O It's pretty similar to this one.

dist-epoch 3y ago

People love bridges which look sleek, thin and like air. They are also cheaper (less materials). But this means there is no redundancy left.

cool_dude85 3y ago

The Mathews Bridge in Jacksonville was clipped by a container ship a few years back and did not collapse. Despite being almost 75 years old, they fixed it up and it opened back up after a year or two. The difference is that the boat did not hit a pylon.

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plastic3169 3y ago

There is this often in HN featured article about bridge engineer analysing bridge collapses in film [1]. It’s about suspension bridges though but the takeaway for me was that when they go they go completely. [1] https://hackaday.com/2015/11/18/suspension-bridges-of-disbelief/ https://hackaday.com/2015/11/18/suspension-bridges-of-disbel...

dathinab 3y ago

At least in the links with the video now you can see that the container ship directly hits one of the two main (and in the central area only) pillars completely collapsing it. No matter(1) the engineering there is no pretty much way to not lose the whole large middle area and left area leading to the destroyed pillar in that situation. Such a collapse crates so much force (tension vibrations etc.) so that the collapse of the section right of the right pillar is not unreasonable. The only question is if the impact should have made the pillar collapse. But a loaded container ship is ... absurdly massive I mean they are like multiple high raise building (but not sky scrapers) standing squished together side by side. So the force it can apply is huge and if cargo moving in it there will be force applied to whatever it crashes into even after the initial impact. And looking at the waves caused by impact with the base it was at least 8m high I think (depending on the container ship). So that wasn't a "slow moving" impact. And even slow moving impacts with container ships can tear apart a solid jetty. So while the US has issues with infrastructure maintenance idk. if anything but building a many pillar bridge would have made any difference. And building a many pillar bridge might not be very viable depending on the under water landscape and water use under the main area. EDIT: Looking at pictures with daylight where you can try to estimate the high of the ship using containers I would say the waves where handwavingly 4 containers high so ~9.5m and it also looks like the ship might have embedded half of the pillars fundament into/under itself (but it's a bit hard to tell to the angle of the picture). I think if that's the case probably the huge majority of bridge pillars of past and presence would have collapsed.

JohnBooty 3y ago
It certainly does not seem reasonable to design a bridge pillar to withstand a direct impact from a massive cargo ship. But I guess I thought that maybe there was... typically some kind of earthen buffer around the pillar to prevent such an impact? That's probably impractical too, I guess. I guess I just didn't realize ~$1bn bridges were one fluky ship accident away from total collapse at any given time. I think maybe I prefer my previous state of ignorance, to be quite honest....
- hgomersall 3y ago

tyingq 3y ago

I did hear one expert on the news say that a better, low-tech defense some bridges have is sacrificial piers in front of the actual ones. I don't know if this bridge had none, or if they didn't get the job done.

bluedino 3y ago

The Bay Bridge in SF has been hit by numerous ships (as large as tankers)

sf_rob 3y ago
The 2007 Cosco Busan incident appears to be a glancing blow. I can't find any information suggesting an analogous impact at any point.

bluedino 3y ago

> It’s surprising that ships capable of doing this damage were probably regularly driving past it, and its safety as a thoroughfare depended entirely on those collisions not happening. There are cities with skyscrapers near airports, which depend on the airplanes not hitting the skyscrapers.

chasd00 3y ago

I don’t drive boats or around water much but I’ve seen “bumpers” on bridge pylons before that make a collision more of a glancing blow and guide the boat to the side. I guess there wasn’t any installed on this bridge? Also, someone on Imgur pointed out that when this bridge was built boats that large weren’t a risk. That may or may not be true but sounds plausible.

fl7305 3y ago
> when this bridge was built boats that large weren’t a risk Doesn't sound plausible to me. Very large Panamax ships were used in the 1970's when the bridge was built.
- 1letterunixname 3y ago
  Sorry, but you're very wrong. A civil engineer on Sky News even raised this issue. https://www.container-transportation.com/worlds-largest-container-ship.html https://www.container-transportation.com/worlds-largest-cont...
  - fl7305 3y ago
    Panamax specifications (320 m length, 32 m width) have been in effect since the opening of the canal in 1914. Some ships were already larger than that back then. The Titanic was about that size. The ship that knocked down the bridge could weigh ("DWT") up to 115 000 tons. Some ships from the 1960s and 1970s: Universe Ireland: Launched in 1968, it had a DWT of over 300 000 tons. Esso Atlantic (1977): DWT of over 500 000 tons. But these were tankers. You're right that container ships were not as big back then. One of the larger container ships when the bridge was built in 1977 was MV Hamburg Express. It was 280 meters long, 32 meters wide, and had a DWT of 50 000 tons. Do you really think a 280 meter long ship weighing 50 000 tons would not have knocked down the bridge in exactly the same way? https://de.wikipedia.org/wiki/Hamburg-Express-Klasse_(1972) https://de.wikipedia.org/wiki/Hamburg-Express-Klasse_(1972)
hnburnsy 3y ago
There were tiny bumpers, two for each pylon, one on each side, but looks like they were place too far out, you can see them here... https://i.pinimg.com/736x/1c/6e/f8/1c6ef8db981c77b1bd780982742d5e65--spangled-banner-star-spangled.jpg https://i.pinimg.com/736x/1c/6e/f8/1c6ef8db981c77b1bd7809827... Ironically there are power lines running in parallel that have much more substantial protection, here you can see the powerline protection and the tiny bumpers... https://patabook.com/news/wp-content/uploads/2024/03/cbsn-fusion-baltimore-key-bridge-collapse-details-rescue-efforts-reactions-thumbnail-2787613-640x360.jpg https://patabook.com/news/wp-content/uploads/2024/03/cbsn-fu...

Lance_ET_Compte 3y ago

In 2013, a tanker ship hit the Bay Bridge (Oakland <--> SF) but didn't do much damage. In 2007, another tanker (Cosco Busan) hit the same bridge dumping oil into the bay: https://www.youtube.com/watch?v=upfjxfl2nRM https://www.youtube.com/watch?v=upfjxfl2nRM. We have a new bridge there now because that one was also damaged in the Loma Prieta earthquake. When the Golden Gate needs replacement, the Marin NIMBY's that didn't extend BART to the north bay are going to be sad (more likely, their children will be).

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ak_111 3y ago

This brings back to memory 911 conspiracy theories. Many revolved around the unlikelihood that a building would collapse the way the towers collapsed just due to knocking out a few floors at the top. But the truth is all these mega structures are quite fragile and can instantly collapse in unintuitive ways.

G0dchi1d 3y ago

The ongoing construction work likely creaty some type of structural integrity issue...

patrickwalton 3y ago

In many structures, catastrophic failures are far more likely than graceful failures.

foxhop 3y ago

these ships have to be boarded by special port captians to make this maneuver.

CydeWeys 3y ago

One factor that a lot of people in this discussion are missing is that buildings are primarily built to resist vertical forces, because gravity is by far the largest force any building (or bridge) ever experiences. Having a large force strike perpendicular to gravity is just not something it's designed for at all. All it ever has to handle in the form of force from that direction is wind, and that's absolutely nothing compared to a fully laden container ship hitting it.

doer1984 3y ago

Ironically, simply bulking up the ground around the piers would have had the ship run aground; at 8 knots the ship would have slowed to a stop within several yards, and suffered minor damage, maybe would have required being tugged back into clear waters. Running aground puts the majority of impact into a downward force absorbed by the earth. It's hard to build a bridge pier that will withstand 200,000 tons of direct impact, no matter how slowly that's moving.

adrianmonk 3y ago
That's what makes sense to me. Ships are designed to minimize drag going through the water. But the friction of the entire hull scraping across the bottom should be MUCH larger and thus able to exert lots more stopping force. Also, if the ground is sloped, it will act like a ramp, lifting the ship out of the water. The loss of buoyancy means its weight will push downward on the ground below it. An increased normal force means more friction, thus more stopping ability.
fl7305 3y ago
> simply bulking up the ground around the piers That is exactly what they did around the pylons of the large Öresundsbridge between Denmark and Sweden.

doer1984 3y ago

Simply bulking up the ground around the piers with loose fill or monolithic concrete would have had the ship run aground; at 9mph (the recorded impact speed) the ship would have slowed to a stop within several yards, and suffered minor damage, maybe would have required being tugged back into clear waters. Running aground puts the majority of impact into a downward force absorbed by the earth. It's hard to build a bridge pier that will withstand 200,000 tons of direct impact, no matter how slowly that's moving.

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hwh47 3y ago

separate but pertinent question: what was the mv dali's air draft? (FSK bridge's clearance is 185'/56m) was the container ship going to fit under the bridge, i.e., perhaps the incident was an aborted attempt to crossing under the bridge?

lolc 3y ago
I'd assume the procedure of how the ship will enter and leave was clear to all involved before it even got close to Baltimore.

hwh47 3y ago

separate but pertinent question: what was the mv dali's air draft? (FSK bridge's clearance is 185'/56m) ...perhaps the incident was an aborted attempt to crossing under the bridge?

doer1984 3y ago

Anyone know about backup steering power on these vessels? I know they typically keep emergency generators, but does this provide adequate steering power?

frankfrank13 3y ago

Someone hasn't played enough polybridge

snarf21 3y ago

Is there a reason we don't force ships above a certain side to always approach a bridge like this perpendicular in the main channels? Seems like a trivial thing to implement immediately and makes this never happen again.