Baltimore Bridge collapse

[Arabian]

Owner of ship that crashed into Baltimore bridge will likely try to invoke 1851 law used to cap damages after Titanic disaster

[VeguerosMAN]

My friend is the senior Deputy Director Marine Accident Investigator at National Transportation Safety Board in DC and is currently in Baltimore investigating this matter. I will post his input when I meet him next week. 

[PuroDiario]

As a structural engineer, albeit having barely exercised the profession…

The collapse occurred for as simple a reason as the pier the ship collided with wasn't designed for such a large impact force. It's a bridge projected in the 1970s, and at that time the norms and loads used were not the same as those used now, and even if tried to it would have been uneconomical to execute. Neither the naval traffic nor the tonnage of the ships were equal to today's and at that time, a load of that magnitude (at 7knots basically 10,000 cars equivalent impacting at once) was not considered. Today, bridges are designed with much larger loads to account for that tail risk, which is very low, (typhoon, earthquakes, etc), but can happen over the bridge's lifespan.

In essence, in case of an accident, the purpose is to mitigate the risk of a chain failure. In Baltimore's case, unfortunately, the ship veers off the navigation channel and impacts directly against one of the main supports, and if that happens, there's no way to avoid the collapse. If that pile's foundation isn't reinforced for that force, then there's no way to resist it.

With modern technology, because that bridge is 50 years old, either it's designed for a very strong impact load or barriers are installed that dissipate the kinetic energy (ship’s movement energy) (here perhaps is one of those few cases were the overly rigid EU regulation trumps US’s more lax approach. That said, if you look at Verazzano bridge here in NY it’s more than protected, so question is why Baltimore’s was not in line with other key National bridges with this type of traffic), against those elements and prevent it from impacting the bridge with such a large force or avoid impact at all if the defenses are robust enough for such a size of ship. That's what that bridge didn't have. And the trajectory caused it to impact directly without touching the dolphins at all (dolphins for those that don’t know are piles driven into the seabed.)

In case the ship had impacted at another point, it could have failed just locally and avoid a collapse. The problem is that this was a bridge with a very large main span of more than 360 meters, mainly supported in two single points flanking the channel, one of which received the impact in full… 

For the conspiracy lovers…accidents and bad stuff happens in the world…every day and at many scales. There have been somewhat recent bridge collisions in China, Spain, and other stuff involving cargo ships as it has been mentioned. Hopefully no ill intent will show here, TBD.
 

What is for sure a pity is that not near enough of the budget is allocated to support, evaluate, maintain, and upgrade critical infrastructure. And that infrastructure spend is used more as a fiscal policy tool that drives votes at the core instead of being the fiscal policy benefits the byproduct of doing what’s right for the electorate.

[Fuzz]

I wouldn't call the Verrazano-Narrows Bridge protected. It may have support piers, but no dolphins around the supports. Instead they use a rock wall around the supports. Reliance on a wide span between supports is the only thing really protecting the bridge. It should have dolphins placed away from the supports to prevent a ship coming close. I suspect they believe the shallower water near the supports is enough additional protection.

As I mentioned in an earlier post, the Sunshine Skyway Bridge is a better example of a protected bridge, learned from experience, as it had collapsed in the early 80s from a ship allision. It uses a combination of dolphins and an island barrier around the support pier.

[CaptainQuintero]

  Are those dolphins able to handle a hit from something as big as that container ship? Or are they more for deflecting smaller boats etc? 

  The force impacting from something as big as container ships must be just ginormous.

[Fuzz]

3 hours ago, CaptainQuintero said:

  Are those dolphins able to handle a hit from something as big as that container ship? Or are they more for deflecting smaller boats etc? 

  The force impacting from something as big as container ships must be just ginormous.

That really depends on the momentum of the vessel. Dolphins are designed to absorb a lot of the momentum and deflect the vessel away from the supports, if not stop the vessel outright (unlikely with vessels getting bigger).

Take as an example, the Ever Given. That container ship is longer, wider and is more than twice the tonnage. When it struck the bank of the Suez Canal, it was going at just over 13 knots (twice the speed of the Dali) and continued a full 5 meters into solid earth before stopping. And the momentum swung the stern around until it lodged in the opposite bank. The force of impact was monumental, but it was still stopped in 5 meters.

Now if the Dali had hit a dolphin or a series of dolphins, the ship would have probably been stopped and/or deflected away. And if the support columns had fenders or island barriers as well, then it is possible the ship would have been stopped before hitting the supports.

The dolphins around the Sunshine Skyway Bridge are supposedly designed to stop an 87,000 gross tonnage vessel traveling at 10 knot. And then the islands (which go all the way down to the sea floor) would absorb any residual momentum.

[Fuzz]

Anyone remember in 2007 when a container ship hit the Bay Bridge, spilling over 50,000 gallons of bunker fuel into the bay? The Cosco Busan was traveling at around 11 knots when it impacted the protective barrier around Delta Tower, leaving a 200 foot long, 10 foot high and 8 foot deep gash along the side of the ship. The Cosco Busan (renamed Hanjin Venezia) was only 65,000 gross tonnage, 265m long and 40m wide, slightly smaller than the Dali.