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Grady, I studied vessel-bridge collision for my Masters and PhD under Dr. Gary Consolazio at the University of Florida. This topic is also my professional specialty as a practicing engineer. From that perspective, I wanted to let you know you did a excellent job explaining the topic and the AASHTO code requirements. I came into this video expecting to have comments or corrections, simply because the topic is esoteric and fairly complicated. But no, you have clearly done your research. Great job, and thank you for what you do. Daniel G.

A two for one Practical Engineering AND Road Guy Rob video?!? What did we do to deserve such a treat!?

7:20 oh my god i never realised it's called a collision as in a co-llision because it's two things crashing into each other, and a-llision when it's one thing crashing into something stationary...

Road Guy Rob is among the most underrated channels. The guy basically works for minimum wage for his daytime job and makes videos for pocketchange in his spare time. His content really should be capable of supporting him as a career. I highly recommend people binge watching anything in his archive that they're curious about. Skip the livestreams unless you're super nerdy, they're a lot content dense and is more just hangin' out with Rob.

Grady, thank you for collabbing with Rob, he deserves way more attention than he gets. I am also not surprised that you are the first "big" youtuber to do so, as you have consistently shown yourself to be a kind and generous person. Thanks for being such a good example.

Regarding Tugs, "What's Going on with Shipping" pointed out that much above 4 knots, tugs really can't do much to alter the path of a large ship anyway - there's simply too much inertia. Now you could force the ships to go slower and use tugs near the bridge, but this is a lot of extra cost and time on every single transit - for something that only occurred due to some sort of failure on the ship. His focus has been on identifying the root cause of the ship losing power in the first place, as there are many other locations such a failure could cause similar problems.

Thanks for the shout out!

6:55 I always smile when I see people in camouflage and high-vis jackets. Like, do you want to be seen or not?! 😂

... the new bike path just ends at a gate... Yeah, that tracks with my bike riding experiences

Single-digit casualties for such a spectacular disaster still amazes me. The early warning system and those cops turned out to be the real heroes.

15:40 Grady: “Back of the envelope” Animator: Here’s the front of an envelope! 😆

3:06 well this just opened up a whole new reason for video game preservation. theres actual history there

I learned some years ago that the best definition of a truss is "it supports loads with math instead of mass" they are great for cheap light support systems, and that is why building roofs and floors are made out of trusses. the drawback is that if you compromise any component of a truss, there is usually no redundancy to prevent failure. thus the logical way to prevent catastrophic failure of truss bridges is to avoid collisions; rather than to try to reinforce them to survive collisions.

The NTSB is one of the most pure and principled government agencies out there. They do one job and they do it incredibly thoroughly.

Honestly the thought that any structure should be able to withstand a direct hit by a ship that large is absurd to me.

Grady, I am a naval architect and marine engineer who spent my career working for oil company marine operations. I was involved with everything from the design and construction of tankers to oil spill response. In fact, our tankers docked at berths 78, 118, and 121 in Long Beach, requiring passage under, or docking next to the Gerald Desmond Bridge. A major point in the discussion of the ability to predict the size of ships when the Francis Scott Key Bridge was built is not valid. We operated three classes of tankers, all built at the Bethlehem Bethlehem Steel Sparrows Point Shipyard, where the Francis Scott Key Bridge is being taken for recycling. The ships were built from the late 1960s to the early 1980s. The tankers were 70,000 DWT, 120,000 DWT, and 265,000 DWT. The fendering and dolphins around bridge piers can be designed not only to guide ships away from the piers but they can be designed to ensure in an allision the ship suffers the damage. I can attest to this, having had to direct the installation of temporary patches covering holes after an allision. One of our tankers hit the Carquinez Bridge. There were two holes, one 10' × 100' and the other 10' × 200'. The bridge had the wooden fendering destroyed and suffered minor damage to the concrete. As for the loss of ship's power, it will be interesting to see the NTSB's findings on the loss of power and inability to regain to regain power. It will also be interesting to find if they tried the main engine in reverse, to stop the ship, or start it going ahead in an attempt to regain steerage. Bob

Dutchie here. We design our water defense for 1 in 1000 to 10000 year events, depending on failure mode and related things. It's pretty recent that we first needed the Maeslandtkeering, which is several decades old, and is one of those structures.

I went to a great deal of effort trying to explain this math to people who were convinced that a ship at a slow speed didn't seem to be that big a deal impacting the bridge. I compared it to an average freight train to give people a reference for the energy. People could associate a freight train at 60 miles per hour with being an incredible amount of force, but they couldn't realize without the mathematics that it was only a tiny fraction of a percentage of the amount of energy of this vessel hitting the bridge. Physics is not intuitive, but it is inescapable.

Guess it wasn’t truss-worthy

20:19 I didn't know Calvin's dad was right about how engineers test bridges

@18:10 - another important note: While 2016 gave us the Panamax expansion which allowed large container ships like Dali to be practical, bulk freight ships in the 100 kiloton range have been around since the 1970s. This event could have happened at any point since the construction of this bridge, it was just more likely to be a coal, petrochemical, or grain freighter.

As a Baltimore City resident and a fan of your channel I have been waiting for this video! Thanks you did NOT disappoint!

Man...Rob and Grady make for one awesome team! I enjoy the energy dynamic that exists between the two!

Nice to see a bike lane on the Long Beach bridge. Sad to see that it doesn't go anywhere. There's a difference between bike infrastructure and meaningful bike infrastructure. People use their car to get from point A to point B. I'd like to use my bike to do the same, but so much bike infrastructure goes from a point where nobody is to a point nobody wants to go to. Off topic I know, but Rob did talk about the bike lane, and covered how it was gated on one end, thereby rending it from potential usefulness to a point nobody wants to go to. That leads to feelings of money wasted as the bike path won't get used very much.

15:40 Sir, that was the front of the envalope.

“Back of the envelope physics” … and then writes in the front of the envelope. I mean, I don’t care, but for a few seconds all I could pay attention to was that being the front of the envelope, and then I saw the Practical Engineering stamp, hey can I buy Practical Engineering stamps? I’d buy those. Oh right where were we? F = ma ok …

In Germany, the Autobahn bridge between Cologne and Leverkusen is being rebuilt. The bridge spans the Rhine river. There was no accident, but the bridge could no longer carry the load. The passage was closed to vans and trucks, and light cars were only allowed to pass slowly over the old bridge. In addition to the old bridge, the new bridge has now been completed. Trucks are allowed to pass through these again. Now the old bridge is being torn down and a second bridge is being built next to it. From the original 4 narrow lanes, the two new bridges will offer 6 wide lanes.

Road Guy Rob!!! Hell yeah!!

Awesome collab with @RoadGuyRob!! I love that guy!!

Baby wake up! Practical Engineering just uploaded!

Last I heard, thanks to Sal Mercogliano's excellent "What's Going On With Shipping?" channel, is they're expecting the main channel in Baltimore to be reopened by the end of May. A portion of the main channel has already been reopened, with a 5-knot speed limit, wind-speed restrictions...and tugs must be attached to ships fore and aft while transiting the channel (not just escorting them). The salvage and recovery operation is truly enormous. Lots of practical engineering going on there!

Nice to see the Road Guy adding some content to the video. Thanks for the colab. He has a great channel and goes into great detail on all things road and traffic with wit and knowledge. "What's Going on With Shipping" has been detailing the maritime side of things with some good channel suggestions as well. He's a good follow.

22:40 I'm "happy" to see that it's not just Italy that builds bike lanes that go nowhere

As a seafarer myself and in Engineering Department of the ship, there are tons of backup machinery in case something fails. I'm talking about 2 pumps each for Lubrication, Fuel, Hydraulics, Air system and Cooling Water (Fresh water and Sea water), and each machinery has 2, meaning Generators and Main Propulsion have their own set of 2. Also all of those machinery have corresponding backup (Auxiliary) pumps which means even if 2 pumps fails (or the power fails) there's still smaller pumps capable of running the ship. There's also an Emergency Generator beside 3 Main Generators (really big ones) so an engine failure on 3 will still able to run the ship as all non-essential machineries like AC and normal lights are off to lower the load. Basically a ship is capable of sailing on Emergency Generator alone if worst comes to worst, theoretically. Now onto inspections, there are 3 port authorities that are somewhat infamous for how strict they are in the world, US Port Authority, Australia's AMSA, and Chinese Port authorities (they're getting stricter every year) not to mention EU countires and Port Authorities. To prepare for going to Port in US alone will cost the ship tons of drills, testing of machineries and cleaning. I'm talking about a month of preparation with minimum of 2 weeks, basically lot of overtime for all crew to test and drill for emergency (these authorities are no joke for us!) as failing for inspection means lots of trouble and more overtime for us to rectify said troubles. Overall my point is, it takes a lot, I mean a lot to cripple a ship. You need to be a bad Engineer to disregard all maintenance operation and it will still take months prior to this incident to f up the ship. I know nobody is perfect and those shipping companies that does wihtheld supplies for ship maintenance and crew living ain't gonna go to these 3 countries (US, Australia and China) and EU in the first place since it will cost them tons with their little budget and low profit and one peep of a seafarer about their living condition and these companies are now under special spotlight every time. They'll be going to more convenient deals that will not give them much trouble with convenient countries, and even then a skeleton ship is still susceptible to ITF (International Transport Workers' Federation) raid and charges, basically a seafarer police that will force companies to treat us better as well as making the ship more safer. TL;DR - It takes a lot to cripple a ship with bad machineries and poor company policies, my conclusion is, a cyber attack is easier way to cripple a perfectly good ship undergoing regular inspection of US Port Authorities and maybe other good Port Authorities. Also I heard Synergy is a somewhat good company.

It's really fun watching this channel because I started watching before college and am now slowly understanding more and more of what is said. I just finished a grueling study grind for a statistics midterm and when you said "if you are familiar with a normal distribution" I went "don't Even get me started". It was really cool to hear about the application of a normal distraction as it relates to the probability overlayed on the bridge like that. It was extremely pertain to my current education.

Also, as a utility worker, that has to foul railroad tracks often, i can say that any time a train is en route past our work zone, there is a clear order of operations that has to take place. 1st of all, we have a flagger, who places a restricted zone within a large area of our work zone, often up to 20 miles each way of our scope of work. This means that any train engineer who approaches that zone needs to radio, not only the tower, but also the flagger to get clearance to traverse that zone, often times at slower speeds too. This alows the flagger to activate our chain of egress operations, which are clearly written down and agreed upon by all workers that at any point throughout the day may be located in the rr row. This order of operations is determined based upon the type of work you are doing in the row. It will clearly state where equipment, and personnel need to get to, and how they get there, should a train need to move through the restricted area. And if at any point during the day, your scope of work changes, work stops, and a meeting is held to determine if changes to the egress plan need to take place. Believe me, it sucks to have to be so meticulous, it often lessens the amount of work that can get done in a given time, especially when your on a major trunk line, where you can have 15 or 20 trains or hyrail vehicles a day. But it ensures that rail workers, utility workers, car motorist at at-grade crossings, train conductors, and train passengers all go home to their families. Perhaps we should have a similar order of operations plan in place when working on high port traffic waterways. If they had, those construction workers would still be going home to their families. Im not putting blame on the crew managers or the companies that had them there, these things are often unimaginable.......until they happen. I would just like it if this horrendous loss of life could lead to better practices.

Channel recommendation about this topic: “Casey Jones - Professional Engineer”. He is a bridge engineer and has very insightful commentary on this kind of thing. “What Is Going On With Shipping” is also great and handles the maritime side of things.

Awesome coverage and colab, Grady!

I very much appreciate efficient, clear, concise scripts. Well done Grady and Rob. You pack in so much explanation (and humour) with no wasted words.

Love what you do and always look forward to your videos Grady!

Hi Grady! Excellent video on the subject. You're right that assist Tugs were not required in Baltimore for the ship transit under the bridge, but if they were, the ship would have needed to be moving at only 2-3 knots instead of 8 knots (like the Dali before it dropped its anchor)) for the tugs to have any hope of guiding such an enormous vessel in the event of a total power loss. As I'm sure you know, the mass of that beasty is astornomical, so each additional knot of speed greatly increases the inertia, and the tugs (even the big ones) only have just enough power to gently nudge such a large ship in any direction, so they would all need to be moving rather slowly for the limited power of the tugs to have enough time to actually have an effect on the ship, once it starts going awry. Incidentally, assist tugs cost $$$ and that increases shipping costs. I'm sure you agree. Just pointing this out for non-boat-nerds.

I'm a bridge engineer who works for a firm in Baltimore. This video was a good explanation of the history and methodology of bridge design without getting too much into the fine detail. The general public really lacks a true understanding of the necessity for probability and statistics in bridge design. They cannot comprehend the magnitude of funding required to "design a bridge for the apocalypse". It's not a few grand more. It's not double the price. It's tens to hundreds of times the price of what we currently design. And with signature bridges like these in the video easily exceeding $1B to construct, it's easy to see how unaffordable apocalypse design really is. We don't have the money to spend $100B on every one of these bridges. No amount of money in the world could pay for that level of design. There are over 560k bridges in the United States, and 60% of them are over water. Many of the 560k bridges are in need of major repair or replacement. Although the vast majority of that 560k are much smaller and simpler bridges, it's still too costly to spare no expense in design. You always must design with a balance of risk and safety. I also just wanted to clarify robs discussion about load ratings of bridges. First, load rating a bridge is a routine procedure. It's done every time a new bridge is built as well as periodically throughout the bridges life, especially if the bridge is deteriorating or doesn't meet current code. As to meeting code, Rob noted that the bridge didn't rate for any design trucks, but he really should have clarified this statement. A "design truck" in bridge engineering terminology is a theoretical load. Current AASHTO LRFD bridge design code specifies HL-93 design loading, which is a combination of a theoretical fully loaded truck (HS-20 truck) AND a fully loaded lane of other vehicles acting simultaneously. Back when that old bridge was built, LRFD code didn't exist. The older code, called AASHTO standard specifications, called for a theoretical truck OR fully loaded lane. Furthermore, the weight of the theoretical truck has increased over time, so it may have been less than the current HS-20 truck back when that bridge was originally designed. My point to all this is to say that a bridge failing a load rating analysis says nothing about the condition of the bridge. Bridges fail load ratings all the time due to being older bridges that were designed to the older code. And a bridge failing to rate also doesn't make it unsafe. It just means that it may need to have a weight restriction and/or lane restriction for trucks. Any unusually heavy trucks will require a permit to cross the bridge anyway, and it is determined well in advance if those permit trucks are allowed over the bridge or if they need a detour. The driver will know this before he even leaves site with his load.

The unexpected thing for me was, how fast that bridge kame down. You somehow expect that tomething so big and heavy collapses slowly (even though that logicaly doesn't make sens), but it took only a few seconds for everything to be over.

I grew up in baltimore, and was devastated that such an important figure of my early life had been destroyed :(

15:24 the power lines had more protection than the bridge lol

Loved seeing Road Guy Rob here!

By far the best, most polished video from this channel yet! Great job!

I just had a lecture today mainly about ship + bridge collisions (among other things), and your video on the Hyatt disaster was shown.

LOVE a good Road Guy Rob collab!

the power lines near the bridge have fenders to protect against collisions but not the bridge itself

This is one of the best documentary programs I watched on any platform. Thank you both!

i had so many conversations about the Key bridge and tons of people saying "Oh, it should've been able to block it" which i had to keep explaining was crazy

Omg!!!! Amazing video AND collab!!! 🙏👏

I've driven on this bridge many times which makes it sad to see it go

Thank you for the video Grady. I have been watching Sal @ What's up with shipping for information on the bridge collapse but it is especially welcome that you have done this. Your information approach and presentation is very easy for me to grasp and I can only say that you make everything clear and concise while providing enough depth that one comes away with a fine overview and quite a bit of detail Peaceful Skies.

Thx for doing this, filming it and sharing it with us. Looking forward to more as you finish them.

7:00 - Even if you DO get an engineer to explain why a massive ship slamming into a bridge pier can cause the bridge to collapse, you still get insane conspiracy theorists arguing that there's no way it could happen. Social media was filled with them right afterwards.

Long Beach resident here. Another important fact about our bridges is the support pylons are on land so it's much less likely to suffer a collision.

Bridge engineer here (PE and SE too) and thoroughly enjoyed this video. Great job on explaining how risk is accounted for in design.

Thank you for this video! As a maritime historian with a background in safety issues, the historical development of risk management, and port history this was such a treat and helps me explain these phenomena to people.

Great as always, Grady. Thanks for looping Rob in. Something I just thought about, maybe an idea for a future episode ... What are the relative advantages for cable-stayed over suspension or truss bridges? I can think of several, but I'm not a CE, so there are probably more issues (cost, span, height, etc.) that play into that decision.

you have the right chemistry for this work and I glad for it. thank you.

Thank you for all of your explanations. There were excellent. I now fully understand the great complexities of designing a Bridge

I didn't know Bill Burr was that interested in Civil Engineering.

As someone from Baltimore that has crossed that bridge many many times, what a great video! Thank you so much for taking the time to put this together and giving us something positive to consider with the loss of such a great historic bridge and loss of life. I have appreciated your content for quite some time. I was pleasantly surprised to see your take on this incident that hits so close to home. Prayers to the families of those affected.

nice to see 2 you tubers working together for a good vid

Great collaboration between two of my favorite engineering channels!! Bravo!

My two favorite creators collab on a video???? We truly don’t deserve such good content ❤️

A few years ago a truck driver (40 tonnes 70 mph) near Pariis hit the pillar of a freeway bidge. It was the first time that a vehicule had brought down a bridge, closing both directions. The driver is no more. A 100,000 ton ship hitting a bridge is the same. No mystery.

Great collab! I'd love to see more of this content!

idk about that old bridge, but even to someone who doesnt live anywhere near America let alone Baltimore, the Key bridge is very iconic, it seems so strange its laying broken in the waters which it used to be so high above

as soon as the bridge collapse I was immediately looking forward to see how you and road guy rob would cover the event, mind was blown when you collaborated on this video, hope you do more in the future!

The "no tug" requirement is a competitive one - if a port requires tugs, the ship captain or operator will go to a port that does not require tugs. So ports do not require tugs to maintain their competitiveness.

A collab I didn’t know I needed! Love RGR

Glad to see our new bridge in your video. It was a real headache dealing with the years of construction, but it makes the crossing easier and safer for all. Take care.

very cool to see a road guy bob feature

"Anyone can design a bridge that will stand for 100 years. It takes an engineer to design a bridge that will barely stand for that time."

Adding to the love for @RoadGuyRob. Always entertaining and realistic about the engineering aspects of road design without taking a side.

This is a colab I been wanting to see. I honestly thought it would never happen but I am glad you guys did. Congrats

15:40 - Brady talks about "Back of the envelope math", but proceeds to do all his math on the front of the envelope. 🤣

This is among my favorite videos you've ever produced and the two person perspective here really did a great job of creating speculative content that was still grounded and not reaching. I really appreciate the content the quality of this video thanks to both of you

Grady thank you for covering this. The Key Bridge is 90 minutes south of me and I’ve traveled over it numerous times.

Love seeing a Road Guy Rob cameo. As others have said, his channel is super underrated and worth checking out!

7:20 technically a bridge is moving, you just have to push hard enough

Would the existing dolphin have been enough to stop the ship, assuming it had hit it head on? I'm sure these "dolphins" are relatively expensive, but so is replacing a bridge and crippling an active port. If you ever get the chance it would be fun to see you do a back of the envelope design for a dolphin or series of dolphins that would've been sufficient to stop this cargo ship (assuming this existing one was not) and aprox. how much they would've cost... very approximate cost

Been waiting to hear your take on this!

Awesome video, I love that you brought on Rob, hope to see more collabs in the future! 🛣️

Thank you for this excellent video. When people complain about why code wants us to do something I'll tell them "Code is written in blood."

that's a lot of pier pressure

I could listen to Rob explain things for hours

Thanks Grady. I knew you'd tackle this and do a great job, as usual. I've been waiting for this video since the event happened. I have high confidence that you present accurate information for us non-engineers.

Layman's Terms: Bridges are designed to resist vertical pressures, not horizontal pressures. That is why earthquakes take down bridges... because of the lateral movement.

That footage is hard to watch when you know people are in their vehicles as it submerges. Heartbreaking 💔

Bow overhang from centerline to me is what got the key bridge as well as inadequate protection around the bridge itself!

An excellent tag-team presentation. Quite informative.

One for the algoritm

Ship goes brrr and bridge goes down

22:24 saw the pedestrian way from below, was going to ask about a bike way, thanks for covering this part

I loved that Grady waited before making a video on this. Really shows he’s engineer first, content creator second, by waiting to acquire in-depth analysis and information.