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The video is surreal, it looks like it barely bumps the bridge and 2 seconds later the entire thing is gone. I don't know what I was expecting, the bridge just
by bastardoperator 3y ago
The video is surreal, it looks like it barely bumps the bridge and 2 seconds later the entire thing is gone. I don't know what I was expecting, the bridge just looked extremely fragile, makes me wonder what other bridges are at risk of an event like this.
- danpalmer 3y agoIt's somewhat counterintuitive how much energy can be in something moving so slowly. I say somewhat, because when you're up close it's much more obvious, but you're right that on a video it doesn't look like much.
- major505 3y agoForce = mass * acceleration, it might be slow but how much does a container shop weighs? 100, 200 thousand tons?
- hangonhn 3y agoThe same go for cars. I was hit by a car which was already slowing down but over ran the line and hit me. The car couldn't have been going more than 10 mph but it was enough force to fracture my knee (the fracture type is also colloquially known as a bumper fracture).
- throw0101b 3y ago> It's somewhat counterintuitive how much energy can be in something moving so slowly. Reminder: Kinetic Energy = ½mv^2 Squaring numbers can make them big in a hurry.
- dweymouth 3y agoBut in this case with slow speed, it's the massive (literally) amount of mass of the cargo ship that gives it an un-intuitively large amount of energy.
- trilbyglens 3y ago8kn isn't super slow
- lupire 3y agosqrt of 100K times weight of a car is 300 cars worth.
- eternauta3k 3y agoNitpick: squaring makes numbers greater than 1 bigger, and numbers smaller than 1 smaller. In this case we're squaring something with units, and we can't say the input is greater or smaller than the output, because they have different units. What we can say, is that v^2 curves upward: it grows faster with increasing v, and slower with decreasing v.
- deltarholamda 3y agoThis disconnect happens with boats quite a lot. For example, I can, by myself, pull a 45 foot grand banks trawler in shallow water. I know because I've done so. But at even very low speeds, I cannot stop it from hitting a pier. I have not tried to do this, but every harbor master has a bunch of stories about people trying to do so and getting a leg or an arm or something squished and pulverized. People who are not boat people rarely recognize these sorts of dangers, which is why so many get hurt on boats. "I can push us off the dock, so I can definitely keep us from hitting it." Nope, Sir Isaac Newton says you're wrong.
- paddy_m 3y agoTo anyone reading this who isn't an experienced boater: If you are invited onto someone else's boat, sit down and shut up during docking, don't talk to friends, let the captain concentrate. Don't help, if the captain wants you to do something, they will let you know. If you think you know better than the captain, and this advice is unknown to you, you don't know better. Being a good guest during docking shows experience and helps get an invite back.
- imoverclocked 3y agoThis advice also translates for general aviation during takeoff, landing and taxiing.
- CIPHERSTONE 3y agoThis is great advice. For myself, docking in windy situations can be nerve racking. The old adage is to only dock as fast as your willing to hit the pier, and for me this means slow as hell. I always let guests know exactly what I want them to do, and to your point, it's mainly to sit tight and let me focus.
- EB-Barrington 3y agoWind, current, tides, your own boat at risk as well as other people's boats alongside... docking can certainly get the heart pumping. (Liveaboard cruiser here)
- hgfghj 3y agoThat ship had a 10,000 TEU capacity and was actually hauling a little under 5,000 TEUs. An empty container weighs a little over 5,000lbs, and a full one can be up to 67,000lbs. If you do the math, you find that it’s just an astronomical amount of momentum, and there’s no effective defense for a bridge that needs support in more than 30 or so feet of water.
- semi-extrinsic 3y agoThrowback to the scene in The Day After Tomorrow where the cargo ship comes to an almost instant halt after impacting a bus wreck under water. For some reason it managed to stand out as ridiculous even in that movie.
- peteradio 3y agoSomebody should do a side-by-side of that scene with this threads scene in gif.
- Gare 3y agoSpeed 2: Cruise Control on the other hand: https://www.youtube.com/watch?v=gBxaGB65TB8 https://www.youtube.com/watch?v=gBxaGB65TB8
- MBCook 3y agoI just saw in a YouTube video yesterday that they actually built a full-size model of the ship (or at least the bow area) and the bit of town it hit. The director didn’t want to use CGI or miniatures. He spent a full quarter of the movie’s budget on that one scene.
- ralfd 3y agoCorridor Crew SFX specialists watching/explaining the stunt: https://youtu.be/_lDM1nAmPHI?t=797 https://youtu.be/_lDM1nAmPHI?t=797 The bow is real, the back of the ship is CGI.
- 3y ago
- anigbrowl 3y agoIt's not the impact, it's the fact that it just keeps pushing. Movies commonly use slow motion and time extension via editing for destruction scenes because (as we've just seen) real time doesn't always look impressive to the untrained eye. Also, there's a lot of mass concentrated in that ship. It's the equivalent of hitting a window with a sledgehammer. Small recreational vessels could probably crash into those pylons all day long.
- naasking 3y agoIndeed, the whole bridge failed because the impact didn't exceed the impact strength of the bridge's material, which means the whole bridge bent until the deflection exceeded the tensile strength of the material. A missile impact with the same total energy would exceed impact strength and would probably have destroyed only part of the bridge.
- AnarchismIsCool 3y agoDid the math, this seems surprisingly spot on, at least from the energy perspective. 100k tons going 7.5 kts is about 160kg tnt equivalent which is a little less than the explosive power of a Mk83/GBU-32, probably not enough to take down an entire bridge, just one span if you're lucky. That said, the issue is the bomb expends most of its energy moving air around, the freighter expended nearly 100% of its energy on the bridge.
- varrock 3y agoThank you for breaking it down like this. As someone without an engineering background, your explanation (along with some Googling for terms and definitions) really helped me grasp what happened. You got me wondering: > the whole bridge failed because the impact didn't exceed the impact strength of the bridge's material When I first read this, it initially threw me off. The cargo ship's impact not exceeding the strength of the bridge sounds like a positive thing, but upon closer reading of your comment, it sounds as if it was the catalyst to the entire bridge collapsing. So, how do engineers balance these properties of impact strength and tensile strength, especially considering large ships channel through these bridges near their pylons frequently? How much engineering goes into the possibility of large structures hitting their pylons?
- samstave 3y ago[flagged]
- manzanarama 3y agoI have no idea what any of this means.
- samstave 3y agoIT was a glitch in posting... I was responding to multipile threads and somehow my comments merged...
- whats_a_quasar 3y agoNo part of that comment made sense. I don't think the problem was that multiple comments merged.
- what 3y agoPretty sure this person uses an LLM to generate their comments.
- throw0101b 3y ago> I don't know what I was expecting, the bridge just looked extremely fragile, makes me wonder what other bridges are at risk of an event like this. The bridge style in question > Conversely, continuous truss bridges rely on rigid truss connections throughout the structure for stability. Severing a continuous truss mid-span endangers the structure. However, continuous truss bridges do not experience the tipping forces that a cantilever bridge must resist because the main span of a continuous truss bridge is supported at both ends. * https://en.wikipedia.org/wiki/Continuous_truss_bridge https://en.wikipedia.org/wiki/Continuous_truss_bridge * https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_(Baltimore) https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_(Balt... So taking out one end basically takes out the whole thing. I would not be surprised that when they build the replacement, it will be a design where the individual components are more self-resilient, like: * https://en.wikipedia.org/wiki/Cable-stayed_bridge https://en.wikipedia.org/wiki/Cable-stayed_bridge The engineering best practices, budgets, and needs may have been different fifty years ago. Cargo ships were also a lot smaller fifty years ago.
- bobthepanda 3y agocable stays are also generally more popular these days because of the differences in material. All other things being equal, concrete is generally a lot cheaper than a steel truss bridge these days
- londons_explore 3y agoIf they play the cards very carefully, they can pull out and recycle all the steel of the old bridge, and use that to pay for a new (cheaper) concrete bridge.
- deleted 3y ago[deleted]
- moritonal 3y agoWhen you play about with game engines long enough, you start to realise that momentum is the key metric to track rather than speed. Especially in water magnitude can be very deceiving but to give some quick math, this vessel had a momentum at impact of about 154,000,000kg⋅m/s. For a car to have equivalent momentum it'd have hit the bridge at 156,580 mph. Humans are just less adept at appreciating mass vs velocity.
- jaxson60 3y agoSpot on.
- amluto 3y agoEnergy matters, too. That hypothetical car has the order of 1 kiloton of TNT of kinetic energy. The resulting blast would have been large. (This is about the estimated yield of the Beirut explosion.) I would rather get hit by a slow moving object than a fast one with equal momentum.
- ithkuil 3y agoIf you're moored on the ground you'd be torn apart in both cases
- amluto 3y agoOn the other hand, if I were hit by a loaded shopping cart at 3 mph and I weren’t allowed to move my feet, I’d probably be okay if I saw it coming. Keep the same momentum but scale the mass down to, say, 200g. Now it’s supersonic, and it will hit with maybe 10x the energy of a musket ball. This would be extremely damaging and likely lethal. (If you make the mass too small, it might go straight through a person, in which case not all of the energy is delivered.)
- ithkuil 3y agoBut the point was that if you were hit with a full container ship at 0.1 mph and not allowed to move you'd be dead. The only reason why a high energy but slow moving object (thus high momentum) is harmless is that it will deliver a small acceleration to you and you won't suffer from the consequences of a high acceleration (which is what generally kills people when they hit something like the ground at high speeds). But that assumes that you're free to be accelerated and move away.
- kazinator 3y agoProbably most of them. A structure like that not designed to bear vertical loads, not lateral ones, other than high winds. The knee is like this too. It lets you stand, run and jump just fine, but you can knock down an opponent with a relatively mild lateral impact to the knee. Much more of the bridge collapsed than you might think, though, far from the impact.
- major505 3y agoBridges are design to withstand a very predictable type and direction of force. It can withstand the lateral wind, but imagine how much force a fully loaded cargo ship can put into it. Once one segment gone the rest is history, because makes the who construction imbalanced.
- mlrtime 3y agoF = MA A looks like 'barely a bump' M is what got the bridge.
- Etherlord87 3y agoI remember when I was a kid, I left a bus, and the bus started moving, and I, not being intimidated by the bus moving very slowly (somewhere between 5 and 10 km/h), didn't move a safe distance away from the bus. I think the bus, due to the nature of its maneuverability, had its tail moving not in parallel to me but slightly towards me - so when it has "touched" (hit?) me, even though I thought it was just sliding in parallel, the force was so strong I made a full 360° turn - and I was a tall and chubby boy. I ended up with no injury, not even a bruise as far as I can remember (who would count bruises as a kid), but definitely with an intuition to respect mass.
- deleted 3y ago[deleted]
- naasking 3y ago> I don't know what I was expecting, the bridge just looked extremely fragile The strongest man in the world probably seems pretty solid. Put him at the bottom of a 3 degree grade and release the brakes on a full tractor trailer and he'll seem fragile too.