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.
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?
I had intended to add that exceeding the impact strength typically results in a local failure near the impact point. A tensile strength failure could happen far from the load and so could be more catastrophic.
I'm not sure if it would have made a difference in this case though, as destroying a main pillar by exceeding impact strength would have by itself transmitted most of the full bridge load to the remaining pillars and that alone may have been enough to exceed the safety margins on the tensile strength that are built into all structures. Unclear without more data, but there was a chance it could have survived in that case, but no chance with the ship consistently applying more and more shearing load.
> How much engineering goes into the possibility of large structures hitting their pylons?
Good questions, I'm not familiar enough with it to provide any further insight, except to say that I believe this bridge was designed long before these huge container ships existed. If they factored ship collisions into the bridge's design constraints at the time, they've no doubt been dramatically exceeded with these huge ships.
I don't think impact strength is factored very much into static structures, tensile strength is more important. It only comes up in very unusual situations like this or 9/11.
Imagine you're holding up a barbell with heavy weights at each end. If the weights on one end drop off, the bar will tilt strongly in the other direction, dropping the weights off on the other end.
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.
He spent a full quarter of the movie’s budget on that one scene.
https://youtu.be/_lDM1nAmPHI?t=797
The bow is real, the back of the ship is CGI.
You deflect it. Failing at that, you direct the force into destroying the ship.
Of course, the best solution is no in-water pylons. But that isn’t always feasible.
Nice immovable object you've got there.
You don’t need to dissipate every joule of kinetic energy in the vessel. You just need to redirect it away from the pylon. That horizontal component can be done with bollards and dolphins sufficiently that even a relatively direct original angle should only damage the fenders. From what I see, there were zero such protections around this bridge.
Nothing can protect against a direct hit. But most hits aren’t direct, and those can be redirected without catastrophic pylon failure.
> You put it ahead of the pylon so that even when the dolphin or bollard is destroyed
Dude, seriously? That has nothing to do with what I was replying to.
If thems be full, that guy would be illegally parked for far longer.
--
What is the traffick-routing-around plan look like? (both sea and land, helicopters cry in lack of TEU)
I would expect they're as close to full as they can get in every trip. They'd be terribly inefficient ways to transport goods otherwise.
Some import products are crazy cheap because cross-planet shipping is basically free because it's the reverse end of a trip carrying valuable stuff. But they mainly applies to ships returning from low development level regions.
Most our exports are bulk not container afaik
Unless ImportYtei.com can get the bills of lading for that ship....
You put in sheet piling 50 meters upstream, and you fill the box with rocks. That's state of the art practice, nowadays, but that bridge was 50 years old.
In 1977 (and in 1972, when construction began), vessels of this size did not exist, and certainly were not allowed in the harbor[1]. But over time, they were given authorization, despite the fact that they could collapse the unprotected bridge like a load of toothpicks.
The real crime here is that there was no retrofit to protect the pylons. It was almost certainly considered and rejected due to cost.
[1]: https://logisticselearning.com/wp-content/uploads/2022/06/Co...
The ship in question here was 10K TEU.
The container vessel in question is tiny compared to e.g. the Seawise giant or Batillus Class.
The smaller VLCCs are dime a dozen and they are 2-3x the weight of the Dali.
Even ports on the US Gulf Coast do not generally have the capability to dock VLCCs.
https://www.eia.gov/todayinenergy/detail.php?id=36232
If Baltimore had been anticipating VLCC traffic in the 70s, then presumably the bridge would have been built accordingly and this incident would not have led to a collapse.
Building a bridge to actually stop the ship is not only infeasible, but it would likely kill (more) people onboard.
"A notable example of dolphins used to protect a bridge is the Sunshine Skyway Bridge across the mouth of Tampa Bay. In 1980, the MV Summit Venture hit a pier on one of the bridge's two, two-lane spans causing a 1,200-foot (370 m) section of the bridge to fall into the water, resulting in 35 deaths. When a replacement span was designed, a top priority was to prevent ships from colliding with the new bridge..."
Source: https://en.wikipedia.org/wiki/Dolphin_(structure)
The MV Summit Venture was a 33,900 deadweight tonnage ship. MV Dali was a gross tonnage of 95,128. Nearly 3× as large. It's questionable whether dolphins would have totally prevented such a tragedy.
Yet similarly, expect dolphins to be brought up as a key component of resiliency for any designed replacement bridge.
But note how the main bridge piers are on giant islands much larger than the pier itself: https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil...
If you really want to make it unblockable you build a bridge+tunnel. https://en.wikipedia.org/wiki/Bridge%E2%80%93tunnel
Reminder: Kinetic Energy = ½mv^2
Squaring numbers can make them big in a hurry.
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.
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.
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.
(Liveaboard cruiser here)
I have a 44ft sailboat. Docking is not easy. People do not realize how difficult it can be
And we got the good tour, because we had a severe storm warning as we visited that ship - the kinda storm in which gusts stop you in your tracks and forces you to lean into it to not fall over. Was a great experience. I wouldn't want to be up there with that kinda wind.
And this was a medium sized clipper, somewhat on the small size.
And based off of that, I kind of want to see a retired battleship or an aircraft carrier. Because now I have an idea of how dumbfounded I'll be at those kinda dimensions. It just doesn't appear that big on photos!
We had a team we work with a lot over here in HH and went on the treasure hunt on the Rickmer Rickmers as an event. That was very nice - they spread a bunch of little puzzle boxes across the ship so you can search for these, walk through the museum and look at stuff. And the puzzles were neat as well - you'd use the compass the actual helmsman used back in the day to figure out where east is to find some clue, count pests in cargo and such. Very recommendable and a lot of fun.
We just didn't climb up the ropes in winds that almost pushed you over on foot, haha.
(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.
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.)
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.
One could be torn apart. If you are glued to the ground and you are pushed away with too much force to resist, you have a problem. You can stretch or move a certain distance and withstand a certain force while doing so, and the product of those numbers is the energy you can remove from the thing hitting you. If the impactor is at a fixed speed, then you can turn that momentum into an energy, but that’s a bit silly. You really can stand still and deliver more stopping impulse to an object moving toward you when it’s moving slower because you can resist for a longer time.
One could collide with an effectively infinitely massive object. But the momentum of that object seems irrelevant — hitting a brick wall on wheels at 25 mph seems much worse than hitting the Earth at 0.1mph despite the Earth having many orders of magnitude more momentum. The impact velocity seems more relevant.
One could get hit by a fast-moving projectile. This is complicated, and neither momentum nor energy seem like sufficient measures. As an extreme example, ultra-high-energy cosmic rays surely hit people on a somewhat regular basis, and I’ve never heard of anyone noticing such an event, despite the energy involved being quite macroscopic.
For a 2 tonne car, my very rough math puts it at more like 2100 mph.
As I said though, I'm far from a physicist so happy to be schooled if I'm way off...
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/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
The engineering best practices, budgets, and needs may have been different fifty years ago. Cargo ships were also a lot smaller fifty years ago.
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.
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.
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.
A looks like 'barely a bump' M is what got the bridge.