Collision of cargo ship with, and collapse of, Francis Scott Key Bridge in Baltimore (26/03)

[WessexEclectic]

The BBC are reporting that because the vessel broadcast a Mayday call, they were able to stop traffic on the bridge. Is that actually realistic in only a matter of seconds?

Apparently this was a toll bridge, so a quick message to control from the Port authority/Coastguard and the gates could be stopped from letting more vehicles onto the bridge in short order.

 

[dosxuk]

Latest reports say they had a couple of minutes warning, and the bridge was closed to traffic as a precaution because of the uncontrolled boat in the harbour, not just when it seemed certain to hit the bridge. Sounds like a well thought out procedure that has worked smoothly when it was needed.

 

[AndrewE]

A ship that size going that speed hitting just about any pier of any bridge would end up collapsing a large part of the structure. For me the big question is why there was so little protection against that happening. There is virtually no protection around the base of the pier to take the brunt of any impact, and only one "dolphin" (effectively a small artificial island intended to stop an errant ship) per side on the approach.

Comments being made this morning that the bridge itself was sound, just that ships have got very much bigger and the precautions against one being damaged by them haven't kept up.
Which begs the question: "is it actually practicable to build a defence against that much mass impacting the base?" The bow of the ship seemed to do the damage, but the bulous bow seen in https://www.marinetraffic.com/en/photos/of/ships/shipid:2810451/shipname:DALI?order=date_uploaded looks as though it is the same length as the ship's bow above. Maybe the momentum is so great that the bow below the waterline can be bent aside whille the superstructure impacts things directly above.
(p.s. if the channel is 50 ft deep that would be an enormous amount of concrete)

 

[edwin_m]

Comments being made this morning that the bridge itself was sound, just that ships have got very much bigger and the precautions against one being damaged by them haven't kept up.
Which begs the question: "is it actually practicable to build a defence against that much mass impacting the base?" The bow of the ship seemed to do the damage, but the bulous bow seen in https://www.marinetraffic.com/en/photos/of/ships/shipid:2810451/shipname:DALI?order=date_uploaded looks as though it is the same length as the ship's bow above. Maybe the momentum is so great that the bow below the waterline can be bent aside whille the superstructure impacts things directly above.
(p.s. if the channel is 50 ft deep that would be an enormous amount of concrete)

Or the bulbous bow could itself push into the structure supporting the pier and assist in dislodging it.

This bridge was opened in 1977, which I think is quite late for truss bridges of this type. Had it been a suspension or cable-stayed structure then it could have had a much longer span, with piers further from the dredged channel. Depending on the underwater profile, this might mean a ship large enough to bring the structure down would run aground before it got near a bridge pier.

 

[David Burrows]

is a comment by a man who really knows about shipping, with a suggestion as to why the ship actually veered accross the channel and hit the bridge.

is an update on the above video.

 

[mpthomson]

there's a lot of metal in that bridge, it's going to have to be cut and lifted off that ship to make sure it doesn't sink. That means getting several very big cranes and barges on site. Then you have to cut and lift the rest........you're looking at months or longer.
On top of which the loss of the road is going to cause access issues

It'll take much less time than that. 4 weeks probably to restore some form of access, that'll be seen as a priority. As above the experise rests with the US Engineer Corps.

 

[swt_passenger]

From the current BBC page:

“The vessel had lost power and issued a distress call moments before - but was travelling too quickly to change course.”

I think people possibly fail to appreciate that after a total loss of power a ship like this has no realistic means of changing course. The rudders are not effective unless the propellers are turning. Indeed power to the rudders would probably be lost as well. It will go where momentum and tide takes it.

 

[GRALISTAIR]

The bridge carried the main i695 interstate (a link in the main i95 Eastern Seaboard route from the border with Canada to Miami) as the most eastern crossing over the Patapsco river.

Yes a very key artery. I have driven it many times.

 

[LNW-GW Joint]

Reports say that Baltimore is a major coal-exporting port, specifically to India for power generation.
There are doubts that the traffic can be rerouted elsewhere easily because other ports are at capacity.
The other major trade from Baltimore is cars and car parts.
So a lot depends on how quickly the port can reopen after the bridge wreckage is cleared.

Bridge engineers all agree there was no significant protection for the bridge piers, as there would be for a new design.
It looks like a new design will be needed, rather than a rapid rebuild of the truss design, and therefore on a long timescale.
Biden has already promised to fund a replacement bridge.
You'd think that there would be a huge insurance claim on the ship's owners/operators.

North America is full of these truss bridges, and yet there are few in the UK.
How is it we seem to have missed out on building this type of bridge?
We seem to have concentrated on suspension bridges (Humber, Forth, Severn etc).

Commentators say there are a huge number of strategic bridges and viaducts in the US that are in urgent need of repair or renewal.
Some background on the truss design:

https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_ (Baltimore)

Continuous truss bridge - Wikipedia

en.wikipedia.org

 

[DelW]

It looks like a new design will be needed, rather than a rapid rebuild of the truss design, and therefore on a long timescale.
Biden has already promised to fund a replacement bridge.

The nearest comparable rebuild I can think of was of the I35W bridge in Minneapolis, which collapsed due to a structural failure in 2007. It was wider than the Key bridge, but not as long or as high. Remarkably, the rebuilt bridge opened less than 14 months after its predecessor collapsed.

North America is full of these truss bridges, and yet there are few in the UK.
How is it we seem to have missed out on building this type of bridge?
We seem to have concentrated on suspension bridges (Humber, Forth, Severn etc).

British and American bridge design preferences have always differed, for reasons that aren't clear to me. By the time of the motorway building era in Britain, long span suspension bridges were indeed the preferred way of spanning wide estuaries. For shorter bridges, concrete box girders were chosen, examples being Medway and Cleddau. The only significant British post war steel truss I can think of is Runcorn - Widnes built in 1961.

Of course we did have our own (much smaller) version of this collapse, with that of the Severn Railway Bridge, partly demolished by out-of-control barges in 1960 and never rebuilt. Five men of the barge crews were killed in that collision and the subsequent fire on board.

 

[swt_passenger]

British and American bridge design preferences have always differed, for reasons that aren't clear to me. By the time of the motorway building era in Britain, long span suspension bridges were indeed the preferred way of spanning wide estuaries. For shorter bridges, concrete box girders were chosen, examples being Medway and Cleddau. The only significant British post war steel truss I can think of is Runcorn - Widnes built in 1961.

I’m not sure about Runcorn-Widnes, it was the obvious example I was first wondering about. But then I read a description of it as being a ‘compression arch suspension bridge’. The wiki article refers to it being like the Sydney Harbour bridge…

 

[Sun Chariot]

A Thomas Bouch designed bridge springs to my mind: the original Tay Bridge.

Wikipedia's entry mentions: "...At either end of the bridge, the bridge girders were deck trusses, the tops of which were level with the pier tops, with the single-track railway running on top. However, in the centre section of the bridge (the "high girders") the bridge girders ran as through trusses above the pier tops (with the railway inside them) in order to give the required clearance to allow passage of sailing ships to Perth."

 

[edwin_m]

Bridge engineers all agree there was no significant protection for the bridge piers, as there would be for a new design.

The power lines crossing the estuary nearby have much more protection and the pylons are set back further from the channel. I assume they were built later.

British and American bridge design preferences have always differed, for reasons that aren't clear to me. By the time of the motorway building era in Britain, long span suspension bridges were indeed the preferred way of spanning wide estuaries. For shorter bridges, concrete box girders were chosen, examples being Medway and Cleddau.

The Americans built the Bay Bridge and the Golden Gate before any comparable suspension bridge appeared in the UK. Subsequently building the Tacoma Narrows bridge may have put them off the idea.

I’m not sure about Runcorn-Widnes, it was the obvious example I was first wondering about. But then I read a description of it as being a ‘compression arch suspension bridge’. The wiki article refers to it being like the Sydney Harbour bridge…

I'd class both Runcorn-Widnes and the Key bridge as hybrids, where the truss forms an arch and the deck is suspended from it. They look very similar. Sydney Harbour is a scaled-up version of the Tyne Bridge (by the same company) and these also have the deck suspended from an arch made up of a truss, but without the continuation of the truss into the adjacent spans. Staying on the Tyne, the nearby Queen Elizabeth (Metro) bridge looks similar to many American designs.

 

[DelW]

The Americans built the Bay Bridge and the Golden Gate before any comparable suspension bridge appeared in the UK. Subsequently building the Tacoma Narrows bridge may have put them off the idea.

Yes indeed, I should maybe have said "long span suspension bridges were indeed our preferred way of spanning wide estuaries", since I was intending to refer only to British practice in that sentence.

I’m not sure about Runcorn-Widnes, it was the obvious example I was first wondering about. But then I read a description of it as being a ‘compression arch suspension bridge’. The wiki article refers to it being like the Sydney Harbour bridge…

I'd class both Runcorn-Widnes and the Key bridge as hybrids, where the truss forms an arch and the deck is suspended from it. They look very similar. Sydney Harbour is a scaled-up version of the Tyne Bridge (by the same company) and these also have the deck suspended from an arch made up of a truss, but without the continuation of the truss into the adjacent spans.

With steel truss structures, I don't think one can set an exact cut-off point at which an arch becomes a girder or vice versa. At some point, as the arch gets flatter, the structural action must change from arch (all bottom chord members in compression) to truss girder (all bottom chord members in tension). The change point will depend not only on geometry but on load case, since concentrated loads may produce tension in some bottom chord members where a UDL on the same bridge would not. The apparently shallower arch of the Key bridge maybe more likely than Runcorn to develop bottom chord tension, but ultimately both will vary in their action under different load cases.
As an aside, the failure point of a masonry arch under a concentrated load depends on whether and when tension is developed in the voussoirs, as the masonry cannot carry any significant tensile load.

 

[AM9]

The power lines crossing the estuary nearby have much more protection and the pylons are set back further from the channel. I assume they were built later.


The Americans built the Bay Bridge and the Golden Gate before any comparable suspension bridge appeared in the UK. Subsequently building the Tacoma Narrows bridge may have put them off the idea.


I'd class both Runcorn-Widnes and the Key bridge as hybrids, where the truss forms an arch and the deck is suspended from it. They look very similar. Sydney Harbour is a scaled-up version of the Tyne Bridge (by the same company) and these also have the deck suspended from an arch made up of a truss, but without the continuation of the truss into the adjacent spans. Staying on the Tyne, the nearby Queen Elizabeth (Metro) bridge looks similar to many American designs.

The US built the Verruzzana Narrows bridge from Brooklyn to Staten Island, opened in 1964. The problem with the Tacoma Narrows bridge was the lack of stiffness in the deck allowing standing waves to be built up under certain wind conditions. The Golden Gate bridge (and the Verruzzana Narrows bridge) were a twin deck desigs giving sufficent buillt-in stiffness to prevent oscillations. For years, the bridge designers grappled with the problem of the additional mass and cost of a stiffer deck (be they constructed with plate girders or open trusses), - then in the '60s the designers of the (original) Severn Bridge, adopted a very lightweight shallow plate constructed box girder deck which had an aerodynamic cross section similar to an inverted double sided aerofoil. This removed the tendency to vortex shed which eventually destroyed the Tacoma bridge. Since then, most large suspension bridges have had a similar low profile deck to much success.

 

[Nicholas Lewis]

A ship that size going that speed hitting just about any pier of any bridge would end up collapsing a large part of the structure. For me the big question is why there was so little protection against that happening. There is virtually no protection around the base of the pier to take the brunt of any impact, and only one "dolphin" (effectively a small artificial island intended to stop an errant ship) per side on the approach.

Those dolphins are the bases of a high voltage power line that crosses in front of the bridge.

 

[edwin_m]

Those dolphins are the bases of a high voltage power line that crosses in front of the bridge.
View attachment 155217

Not the same dolphins. There are two much smaller ones much closer to the bridge and two more on the other side.

Bing Maps

Map multiple locations, get transit/walking/driving directions, view live traffic conditions, plan trips, view satellite, aerial and street side imagery. Do more with Bing Maps.

www.bing.com

At about 9:47 in the video below it's clear that the impact wasn't head-on, so the bulbous bow possibly missed the protection around the pier. It also suggests that the top of the vessel or the container load hit the bottom of the truss where it curved down into the pier - I'm not entirely convinced the video demonstrates that and the damage to the ship may have been due to the bridge falling onto it, but the commentator may know more than what is shown.

 

[JD2168]

The operation has now changed to a search & recover operation rather than Search & Rescue. It is believed that the workers are now dead.

RIP to the workers killed in this terrible accident.

The container ships black box has been recovered by investigators so this may be able to find out what happened.

 

[swt_passenger]

Not the same dolphins. There are two much smaller ones much closer to the bridge and two more on the other side.

I thought when I saw one yesterday it seemed that set of four were floating, and possibly navigation marks? Does the US make charts available online? (yes they do)

 

[edwin_m]

I thought when I saw one yesterday it seemed that set of four were floating, and possibly navigation marks? Does the US make charts available online?

A chart with tracking is visible on this video at about 1:24. I think they are shown as the pink diamonds, whereas navigation buoys are shown like leaning chess pieces.

The container ships black box has been recovered by investigators so this may be able to find out what happened.

The sequence of events now seems fairly clear. Accounts from the crew and pilots will be important in understanding why the power failed and how they responded to it.

 

[Nicholas Lewis]

Not the same dolphins. There are two much smaller ones much closer to the bridge and two more on the other side.

OK thought they were navigation markers as they are lit and not sure they would have afforded much protection to the inertia in 100k tonnes of ship moving at 7 knots.

Bing Maps

Map multiple locations, get transit/walking/driving directions, view live traffic conditions, plan trips, view satellite, aerial and street side imagery. Do more with Bing Maps.

www.bing.com

At about 9:47 in the video below it's clear that the impact wasn't head-on, so the bulbous bow possibly missed the protection around the pier. It also suggests that the top of the vessel or the container load hit the bottom of the truss where it curved down into the pier - I'm not entirely convinced the video demonstrates that and the damage to the ship may have been due to the bridge falling onto it, but the commentator may know more than what is shown.

Another video has appeared on youtube from slightly different angle although quality not great

 

[Towers]

One thing that I found surprising was footage of the former bridge showing what appeared to me precious little protection to stop anyone from falling off it; it looked very much as though the edges of the carriageway were lined with standard concrete barriers and that was about it?

 

[Nicholas Lewis]

One thing that I found surprising was footage of the former bridge showing what appeared to me precious little protection to stop anyone from falling off it; it looked very much as though the edges of the carriageway were lined with standard concrete barriers and that was about it?

Yeah that struck me as offering very little resilience should there be a road traffic accident but guess deemed adequate. Certainly on the Dartford crossing its a lot higher.

 

[Peter Sarf]

OK thought they were navigation markers as they are lit and not sure they would have afforded much protection to the inertia in 100k tonnes of ship moving at 7 knots.

Another video has appeared on youtube from slightly different angle although quality not great

That video looks to show the pair of concrete A pillers sticking up above the water being moved away from under the steel it is meant to support. Moved away in the same direction of travel as the ship. I cannot tell whether the strike was above the water surface or below. But it looks like the ships superstructure or containers did not strike the truss work until that collapsed onto the ship.

I had wondered if the strike had been to the truss work as it arches down to the A pillars but that video rules that out. If it had then I guess the steel truss might have been moved further in the direction of travel of the ship.

Latest I heard was that six workers on the bridge are missing and that the road traffic had just been stopped in time. So could have been worse but still the loss of six lives.

Also I was interested to hear on BBC news that divers recovered the black boxes. So that (divers) suggests the ship was damaged below the waterline. I guess that means the pair of A pillars was struck below the waterline.

If the A pillars had not given way then then the bridge would have survived. But if that led to the ship sliding past, as looks possible, then its superstructure and/or containers would have probably hit the beginning of the arch and brought the bridge down anyway.

I assume the A pillars are concrete.

---

EDIT
Update on BBS news.

I read that the bodies of two workmen have been found in a red pickup truck. The remaining four are believed to be in other vehicles that are buried amongst concrete (the road deck ?) and the metal structure. Apparently too dangerous for divers to get near.

Quote below

Divers working to reach vehicles buried beneath the collapsed bridge have faced dangerous and difficult conditions.

At a press conference earlier, Ronald L Butler from Maryland State Police said divers had “exhausted all search efforts” in the areas around the wreckage and had not yet been able to reach the vehicles.

“Because of the superstructure surrounding what we believe are the vehicles, and the amount of concrete and debris, divers are no longer able to safely navigate or operate around that,” he said.

“Based on sonar scans, we firmly believe that the vehicles are encased in the superstructure and concrete that we tragically saw come down.”

The FBI agent leading search, Supervisory Special Agent Brian Hudson, has also said there is a “very dangerous situation underwater”.

“With the rubble still settling, it’s not a great spot for divers,” he told CBS, the BBC’s US partner.

“It’s incredibly black water, as the sediment gets kicked up. And there’s also a significant current moving underwater as the tides change.”

He added that the recovery efforts could take as long as a week.

Although "recovery efforts" might refer to recovering the bodies I feel that includes removing the steel work (and maybe the concrete deck if it has folded) from the channel first as it is in the way. A week is quicker than some suggestions for clearing the shipping channel.

 

[DelW]

Also I was interested to hear on BBC news that divers recovered the black boxes. So that (divers) suggests the ship was damaged below the waterline. I guess that means the pair of A pillars was struck below the waterline.

I think that the removal of the data recorder was by coastguard officials on board the ship, rather than by divers?

Although "recovery efforts" might refer to recovering the bodies I feel that includes removing the steel work (and maybe the concrete deck if it has folded) from the channel first as it is in the way. A week is quicker than some suggestions for clearing the shipping channel.

Surely a timescale of a week can only refer to recovering bodies and possibly vehicles they're in?

Clearing the steelwork will be a massive operation, even with the resources of the US Army Corps of Engineers and civilian marine contractors. There will be huge forces locked within the distorted steel members, meaning there's likely to be sudden and violent movement of the remains as sections are cut. That means that remote control cutting or possibly explosive demolition may be the only safe option, but that takes time to resource and plan.

The ship has also suffered severe damage to the hull at the bow, which may need a temporary repair before it can be floated off the the bridge foundation.

The cost of closing the port (including losses incurred by all the vessels now trapped there) means that enormous resources will be applied to clearing the lane, but even so, it will surely be many weeks before the channel is cleared.

 

[stuu]

I would assume that being close to the world's largest naval base is handy, the US Navy must have some useful ships and equipment for clearing shipping channels

 

[najaB]

My SWAG is that it will take a couple of weeks to gather all the information that investigators need to reconstruct the accident sequence, then clearing the channel will proceed relatively quickly.

I'd be surprised if the port was closed for more than six weeks.

 

[LNW-GW Joint]

It's chilling to see in those videos the trucks and cars crossing the bridge in the last few minutes/seconds before the ship collided with it.
They would be completely unaware what was happening behind them, and how close they came to being casualties in the water.

Digging around Wiki about truss bridges, I was impressed with this rail truss bridge at Sciotoville, Ohio/Kentucky.
It dates from 1916 and carries a CSX route over the Ohio river.
Also more generally that the truss bridge design process was difficult until computers became available to do the complex load calculations on each truss member.

Sciotoville Bridge - Wikipedia

en.wikipedia.org

Early estimates of insurance claims are around $3 billion, which would be the largest ever marine insurance loss.
Lloyds of London is the biggest insurer of such risks.

Baltimore bridge collapse could lead to record insurance loss, says Lloyd’s boss

Bruce Carnegie-Brown says disaster could cost billions and result in largest single marine insurance loss ever

www.theguardian.com

Barclays said claims for damage to the bridge alone could reach $1.2bn, and there could also be liabilities of between $350m and $700m for wrongful deaths.
Hundreds of millions of dollars more would probably have to be paid out for business disruption caused by the port’s closure.

 

[DelW]

Also more generally that the truss bridge design process was difficult until computers became available to do the complex load calculations on each truss member.

Pin-jointed trusses are very easy to analyse, A-level applied maths is all that's needed.

Once the connections can carry moments, the design calculation gets more complicated, and the more complex structures require solving large numbers of simultaneous equations that effectively need a computer. That can make for more efficient and hence more economical designs though.

Then if it includes variable section properties or complex joints, you may have to get into finite-element analysis, which is another level of complexity.

 

[Peter Sarf]

On timing I can imagine it taking the best part of a week to bring in and assemble a floating crane and large barge. Then maybe a day to lift each section of truss out. How large a section of truss depends on its weight and any structural integrity left in the truss !.

This might be the stage where the vehicle(s) with trapped people in will then be retrievable.

Then I wonder if the deck has to be removed or if the channel is deep enough. I suspect the deck will be embedded in the bottom of the channel so not easy to get attached to and lift. Possibly now in smaller individual panels ?.

It is only (!) the central part across the shipping channel that needs urgent removal.

I wonder how much road congestion etc is being caused by the loss of the bridge. For instance the problems caused by loss of the road crossing might be responsible for more than the six deaths so far. Extra pollution on alternative routes that get over congested and more accidents. Not significant per month but maybe over a very long time. How long for a replacement bridge ?.