Matt Dursh
@MattDursh
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Professional Engineer • Bridge Design • Civil Engineering • Design Build • Accelerated Bridge Construction • e/acc
Tampa, FL
Joined September 2015
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Bridge design for vessel collision. A🧵
The main span of the Francois Scott Key Bridge is 1300 ft. It also has 185 ft of clearance, making this a massive bridge.
This type of bridge is considered complex.
Baltimore is in for a long haul before replacement. Here is why.
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There are many things left to talk about here, but on a plane now.
I specialize in bridge design of long bridges over navigable waters.
Thanks for reading and happy to answer all questions.
12/12
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Modern bridges deal with vessel collision two ways.
The first is to use a dolphin.
This is a mass of rock, sand, and steel that serves to stop the vessel before it makes contact with the bridge.
Likely the new bridge replacement will use a dolphin as one method.
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This bridge was going to fail from this event. It simply was not designed for an equivalent static force that is well over 3 million pounds.
The container ship, assuming the navigation channel is centered, veered over 500 feet off course.
Why did the whole thing fall?
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The Baltimore bridge collapsed because it got hit by container ship. What failed first?
It appears the bow of the ship made contact with the vertical columns that supported the truss superstructure, causing it to have a cascade failure.
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We design modern bridges for ship impact, but this was not always the case.
In 1980 the Sunshine Skyway Bridge also collapsed from vessel strike.
The photo below is the original Skyway. Similar bridges and identical failure.
The Skyway collapse changed bridge design.
2/x
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The whole truss fell because this is a continuous bridge.
This means that the 3 span unit behaves as as one. If one span fails, the maximum dead loads redistributes.
This provides benefits to load resistance and is how we design modern bridges for this.
How?
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Baltimore is going to be without a critical bridge for a long time.
Tampa's Skyway bridge took 7 years, but this will be done sooner, hopefully much sooner.
What needs to be done? Well, a lot.
Can the approach spans be salvaged?
9/x
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The second is to design the bridge to take the vessel strike and resist the event.
This is a massive undertaking with a central focus: don't collapse.
We will see localized failures, but maintain global stability.
This load could be well over 3 million pounds.
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To resist that much load to stop a vessel, we need a flexible bridge and a lot of foundations, such as piling or drilled shafts.
Typically this is more foundation needed than to simply resist earthquakes, hurricanes, and every day loads.
So where do we go from here?
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The approach spans are likely fine.
But are they tall enough to support the new main span? Does the bridge need more vertical clearance?
Officials will nees to ask... do they fully replace the bridge in full, or attempt to reopen sooner with only the main span?
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The main span is not easy to design or build, unless they make a decision to go to a smaller span bridge (less than 375ft).
But that comes with new challenges particularly with how close the piers will be to the navigation channel.
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The navigation channel has fully reopened after the collapse of the Francis Scott Key Bridge.
A total of six bridge spans fell after the M/V Dali struck the bridge.
It took 76 days to remove over 50,000 tons of the wreckage.
A 🧵 on next steps to rebuild the Key Bridge. (1/8)
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@xtbot
Tunnels have their own sets of challenges. A bridge can be rebuilt here designed to prevent a tragedy like this again.
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Recent footage on the progress at the Francis Scott Key Bridge.
As explained by a Professional Engineer and Bridge Designer.
My first video! What do you think?
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The Design Builder has been selected for the rebuild of the Francis Scott Key Bridge!
The design of the replacement bridge begins now. This is what happens next.
A 🧵 about bridge design and construction. (1/12)
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The collapsed steel spans should not be reused.
When verifying safety for traffic, many members will be compromised due to permanent deformations and other signs of distress.
The continuous bridge was built using temporary towers, this changes the "locked-in" stress.
1/x
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One of the first vessels to transit the Limited Access Channel at the Francis Scott Key Bridge.
Gives a sense of scale of just how large the Dali is.
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Bridge Analysis to remove the Francis Scott Key Bridge. A 🧵
Extracting the steel at the bottom of the Patapsco River will be complex.
The structural steel arch still has capacity to it, similar to bending a paperclip.
How do you determine the sequence to cut? (1/x)
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How will the Francis Scott Key Bridge be rebuilt?
The Transportation Authority says it will be a Progressive Design Build.
The winning contractor will be chosen by qualifications and the construction cost provided later.
A brief 🧵 about contracts for roads and bridges. 1/10
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The deep draft navigation channel at the Francis Scott Key Bridge recovery has been fully restored.
The Fort McHenry channel is 50 feet deep to the mudline and and is 700 feet in width.
The vertical clearance is 214 feet due to the nearby overhead electrical lines.
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The Kinser Bridge has collapsed near Greenville, Tennessee from severe flood waters of the Nolichuky River.
This was caused by scour on the foundations of the bridge, removing the supporting mudline soil from the piers.
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This hydraulic grabber is about to put in some serious work at the Francis Scott Key Bridge recovery.
It's self weight is 400,000 pounds and it can extract over 2,000,000 pounds.
The capacity will be limited by the crane that wields it.
I cannot wait to see it in action.
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The approaches to the Lake Lure Flowering Bridge in Chimney Rock, North Carolina has scoured away.
This historic three span arch bridge was built in 1925 and carried traffic until a new bridge opened in 2011.
The bridge supported an expansive garden before Hurricane Helene.
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A huge 440 ton section of the Francis Scott Key Bridge being transported.
It was partially submerged prior to lifting.
Steel truss section is so large it is being floated to disposal instead than placed on a barge.
The scale of this operation is incredible.
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It has been just over 30 days since the collapse of the Francis Scott Key Bridge.
This video reviews the progress made in the recovery and the scale of the mobilization.
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The Dali has been refloated and is no longer at the Francis Scott Key Bridge site!
Five tugboats are transiting the vessel to a local marina.
There the remainder of the steel and concrete on the bow will be removed and all containers offloaded.
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The refloat of the MV Dali away from the Francis Scott Key Bridge.
Now moored at the Seagirt Marine Terminal.
The 50 foot full depth navigable channel has been partially restored with a 400 feet horizontal clearance
All commercial vessels can now enter and exit the port.
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Before and after photos of the Francis Scott Key Bridge concrete column sitting on the Dali.
A full depth saw cut was made through the concrete column for removal.
The inner hollow core of the column can be seen.
Incredible work being done at the recovery effort.
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The Francis Scott Key Bridge collapsed after vessel collision from the MV DALI.
This tragedy was entirely avoidable. A small change in course would have prevented ship impact.
All means to control the the motor vessel were unavailable.
A 🧵 about the unseaworthy Dali. 1/9
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Time is of the essence to rebuild the Francis Scott Key Bridge. I will provide updates as milestones are reached.
I am a Professional Engineer, bridge designer, and design build project manager for heavy civil infrastructure projects.
Thank you for reading my 🧵. (12/12)
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A temporary channel has opened at the Key Bridge.
The first vessel to use the temporary channel is the tugboat Crystal Coast.
It is pushing a fuel barge carrying jet fuel that supplies the Department of Defense.
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Bridge collapse in Dresden, Germany.
The Carola Bridge fell into the waters of the Elbe River on September 11.
A 🧵about bridge design.
(1/9)
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Great angle of the controlled demolition of the Francis Scott Key Bridge.
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First views from atop the Dali at the Francis Scott Key Bridge recovery.
Also confirmed is the use of precision cutting for a controlled demolition of the truss.
Critical connections have been marked on the structural steel.
There are pre cuts made into the webs of the beams.
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@10x_er
she made her tik tok, then watched her tik tok. just like the predictable clicking of a clock.
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The 35' depth limited access channel at the Francis Scott Key Bridge recovery will open ahead of schedule.
Vessels will transit on the left side of this photo starting April 25.
This is wonderful news and demonstrates the quality work being done.
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New sonar images of the Francis Scott Key Bridge shows incredible perspective and details. 🧵
This is the main span channel pier opposite of the Dali impact.
You can see the detail of the column, footing, and truss.
(1/3)
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Largest crane pick seen so far for the Key Bridge.
Full depth section of the truss. Top and bottom chords.
This is with the Chesapeake 1000 ton crane. First pick since mobilizing on site?
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The worst flooding in over 150 years in Vienna, Austria as the Danube River continues to rise.
Bridge piers resist forces from the water, remaining stable as the soil that supports the foundations scours away.
Maximum stress scenario in bridge design.
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The wreckage of the Francis Scott Key Bridge has almost been fully removed.
One section of the truss remains before the full width reopening of the channel.
That section was partially resting on the Dali.
Latest schedule update indicates full restoration by June 10th.
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Technology Optimism
Effective Acclerationism
American Exceptionalism
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The steel truss of the Francis Scott Key Bridge is being removed from the bow of the Dali.
The reinforced concrete deck and floor beams that supported it can now be seen.
The extent of damage on the Dali is starting to show.
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Precision cutting charges have been placed on the Francis Scott Key Bridge.
Detonating the charges and sending the steel truss into the water is set for Saturday afternoon.
Surprisingly, the crew on the Dali is to remain aboard and shelter in place during the event.
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A bridge has partially collapsed after a barge collision with a pier.
The Pelican Island Causeway is the only route on and off the island in Galveston, Texas.
Railroad spans collapsed, causing damage to the vehicular bridge.
A 🧵 about this bridge and next steps. (1/10)
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The final steel truss section of the Francis Scott Key Bridge has been pulled from the Patapsco River.
It was well embedded in the mudline, taking "extensive operations" to extract it.
The Chesapeake 1000 crane carried this piece to Sparrows Point for disposal.
Great work.
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This is an 880,000 pound crane pick at the Francis Scott Key Bridge.
Less than 1 min explainer video by a Professional Engineer and Bridge Designer.
Next video is in the works.
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More angles of the controlled demolition of the Francis Scott Key Bridge.
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The hydraulic grabber is putting in some serious work at the Francis Scott Key Bridge recovery.
Keep in mind the yellow grabber itself is 29 feet tall.
Here it is removing some floor beams and stringers.
Those pieces of structural steel supported the concrete deck.
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"No one is coming to save you, so go out in the world, build good things, useful things, things that people like and use." -
@IterIntellectus
e/acc and the Techno-optimists are creating.
Come build with us.
Ok guys, gather around.
As I feel obliged by the state of matters, I will give you my very dumb take on the current thing:
As I see it now, this is war.
Ideological, philosophical, memetic.
It’s not a war for land, power, or money (even though these are at stake in the short
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the feedback and response that i have gotten on my video is really incredible.
thank you. will keep more videos coming.
Recent footage on the progress at the Francis Scott Key Bridge.
As explained by a Professional Engineer and Bridge Designer.
My first video! What do you think?
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Thank you for reading my 🧵.
I am a Professional Engineer, a bridge designer for long bridges over water, and design manager for Design Build projects.
I will continue to post about civil infrastructure.
Fall 2028 reopening is an aggressive schedule that can be done. (8/8)
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The vertical clearance for the rebuild of the Francis Scott Key Bridge has not been finalized.
Existing bridge had a navigable clearance of 184 feet. Recently built electrical lines now controls at 214 feet.
A 🧵 on construction cost of transportation infrastructure.
1/x
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Here is how the precision cutting demolition will be done on the Francis Scott Key Bridge.
The steel truss sitting on the Dali will use explosive charges to cut the steel.
The placement locations and timing of the charges will cause it to fall off the bow and into the water.
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The significant risks of reusing the fallen spans far out weighs the potential schedule benefits.
It is important to consider this as an option in the bridge recovery, but I strongly advise against it.
Rebuild with new American steel.
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My bridge under construction in Florida.
30 inch concrete piles are in a temporary steel template.
Templates are used to install the pile plumb and in the correct position.
These are driven into the ground using a diesel impact hammer, striking the pile 1,000s of times.
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Devastating Nolichucky River flooding from Hurricane Helene has collapsed two bridge spans on Interstate 26 in Erwin, Tennessee.
Soil embankment behind bridge abutments, where a bridge starts from land, was washed away by the flood waters.
🧵 about highway bridge design. 1/6
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Engineers are installing devices on the Francis Scott Key Bridge to measure forces inside the beams.
The loads and stress seen by the truss will change during each step of removal.
Depending on the statics, it may increase or decrease.
What device can they use? (1/3)
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Tampa General Hospital is on Davis Island in Tampa Bay, which is an area that very vulnerable to storm surge.
The hospital placed a temporary barrier that resists up to 15 feet of storm surge, allowing them to maintain operations.
It worked well!
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New tunnel completed in Virginia.
One more to go after the tunnel boring machine makes a U turn.
Awesome.
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Vessel collision on a cable stayed bridge in the Netherlands.
The structural steel of the bridge was struck because the vessel violated the vertical clearance of the waterway.
The bridge will be inspected and repairs done to the steel superstructure.
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More sections of the steel truss getting removed.
When the biggest crane is putting in work it is a sign of progress being made.
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First look at underwater survey of the Key Bridge.
Good sign is there are still large portions of intact bridge to work with.
But where the truss has failed it is fully collapsed on itself.
It also is partially under the mudline, increasing the loads on the crane.
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Short video on a 440 ton section of the Francis Scott Key Bridge.
Includes some info about the Chesapeake 1000 crane and naming of the truss itself.
Included unit conversions for you metric system enjoyers.
This info will be used as reference material for an upcoming video.
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that masculine urge to hire all your friends to go and build something never done before.
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Evaluate what happens after the cut, does the structure move and reposition?
Does the structural steel have the capacity to resist the salvage loads and avoid rupture during lifting?
We will see the largest crane pick they can make with the 1000 ton crane.
(5/5)
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The Francis Scott Key Bridge replacement has received Federal environmental approvals.
The process was expedited because the new bridge will be the same number of lanes and built on the existing footprint.
This avoids a long procedure of evaluating impacts for the rebuild.
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Thank you for reading my 🧵.
I am a professional engineer, bridge designer, and design manager for design build heavy civil infrastructure projects.
If interested in more content like this, make sure to follow and distribute.
10/10
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Work Zone progress at the Francis Scott Key Bridge.
1. Chesapeake 1000 clearing steel from temp channel.
2. Weeks 533 picking containers from Dali.
3. Deck being crushed and dredged. This reduces load and provides access to remove the second half of the truss.
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The gas and electric utilities in proximity to the Francis Scott Key Bridge Recovery.
What can be considered to enhance safety and facilitate schedule?
Can the electrical transmission lines be de-energized and temporarily removed to enable crane activities on both sides?
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Half section of the Francis Scott Key Bridge truss.
Top of the bridge is on the left in photo.
Looks to have been extracted from the mudline.
Chesapeake 1000 doing great work.
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Segmental concrete bridges.
This type of bridge design uses a specialized launching gantry to install the superstructure.
The construction methodology in this video is called span by span construction.
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One of the last pieces of the Francis Scott Key Bridge steel truss has been removed.
This was partly resting on the Dali.
This section suspended the vehicular concrete deck below it
The next step will use the hydraulic grab to extract the floor beams and deck from the mud.
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A new temporary channel has opened at the Francis Scott Key Bridge.
Vessels will need to sail near the electrical towers.
The Fort Carrol temporary alternate channel is 300 foot wide with a vertical clearance of 135 feet and a controlling depth of 20 feet.
Good progress!
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How it started vs how it's going at the Francis Scott Key Bridge recovery.
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Bridge design for extreme storms. A 🧵
Two spans of the Phong Chau Bridge in Vietnam collapsed during Typhoon Yagi.
This bridge failure mechanism is one of the most common.
What happened and how is it prevented? (1/10)
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The fender did it's job in redirecting the vessel away from the bridge piers and back to the channel.
This one is made of prestressed concrete piles.
Each support is a vertical plumb pile and an angled battered pile that absorb the collision energy.
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How it started vs How it's going.
Francis Scott Key Bridge edition.
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great read if you want to know more about what i do.
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Walter's Dam in North Carolina, east of the Smoky Mountains National Park, has not failed!
County Mayor initially reported of catastrophic failure.
But the power company has flood gate control and the Waterville dam is performing as expected.
Evacuation still underway. 🧵1/3
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The above water photography does not capture the significant challenges underwater.
What is not seen is the reinforced concrete deck that is still attached to the steel.
A web of rebar and concrete poses significant hazards.
It also is heavy. (3/x)
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terrible to see a bridge collapse.
we design modern bridges for vessel collision, but this one was built in the 70s before standards changed.
very similar bridge to Sunshine Skyway collapse in the 80s, which is what changed the design codes.
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Engineers will use hand calculations and 3D finite element models to perform static analysis.
This will determine how the structure is supporting itself and how it's weight is distributed.
Cut points and lift locations will be evaluated for several criteria. (4/x)
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You start with the existing bridge plans.
They will be used to determine the weight of the bridge and the capacity of the steel members.
Lift points will be established to confirm the damaged steel can support itself during removal.
3D survey will be used extensively. (2/x)
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Temporary steel towers were used to support the bridge during construction.
Their use and timing of removal dictates when each steel member is fully engaged to support the self weight of the bridge.
If one is removed too soon, or not used at all, this changes everything.
2/x
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Crane on the right is lifting a man basket with two workers inside.
The Francis Scott Key Bridge was the second largest bridge of it's type in the world.
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The collapse of the Francis Scott Key Bridge caused a loss of life for six construction workers maintaining on the Key Bridge.
Repairing the riding surface of the bridge deck to improve driving conditions.
Performing important maintenance.
If only the Dali had done so. 9/9
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The Dali has exited the Port of Baltimore and is heading to Norfolk, Virginia.
The containers have not been offloaded yet.
Portions of the reinforced concrete deck has been removed.
The collapsed column of the Francis Scott Key Bridge still remains on the bow.
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The precision cutting of the Francis Scott Key Bridge was a success.
Locations where charges were placed on the structural steel truss can be seen.
The damage to the Dali is extensive but is planned to refloat next week.
Navigation channel will be reopened soon.
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Removing the collapsed Francis Scott Key Bridge. A🧵
These are some of the challenges and solutions that should be considered.
Time is of the essence and safety is paramount.
Accelerate Bridge Construction
(1/X)
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Concrete pile driving using a diesel impact hammer.
Thousands of hammer blows are used to advance the pile and achieve capacity.
Gauges attached to the pile measure acceleration and strain during each strike.
We use that info to determine the bearing capacity of the pile.
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Unless the bridge was rebuilt in the same order with the same tower locations, there will be changes to the self weight stress in the steel.
Would that change result in overloading of any member or connection?
Only rigorous engineering can answer this with confidence.
3/x
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e/acc is about to reach escape velocity.
extreme optimism is proliferating.
morale maxxing will continue.
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New machining. New tooling. New frontiers.
e/acc means and methods are for builders
“sovereign AI infrastructure” — multibillion dollar growth opportunity in coming years
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Thanks for reading my 🧵.
I am a Professional Engineer and Bridge Designer. I post on X about bridges, civil engineering, and infrastructure.
The demolition and removal of the Carola Bridge is underway and will be completed soon. Will provide updates.
(9/9)
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