Matt Dursh
@MattDursh
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Bridge Designer • Professional Engineer • Design-Builder • Accelerated Bridge Construction • e/acc
Tampa, FL
Joined September 2015
Site work for the rebuild of the collapsed Francis Scott Key Bridge finally begins next week. This 🧵 overviews the what will occur next on the reconstruction of the Key Bridge. 1/7
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Do not ever straighten rebar like this. I cannot emphasize how bad this is for structural integrity of reinforced concrete structures.
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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. 1/x
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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. 6/x
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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?. 4/x.
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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. 3/x.
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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?. 5/x
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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. 7/x.
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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?. 8/x.
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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?. 10/x.
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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. 11/x.
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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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@DotDotJames The only application for recycled rebar in concrete elements is in non-structural applications. A sidewalk would be satisfactory since this is only shrinkage and temperature steel.
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Francis Scott Key Bridge rebuild and bridge design update. This 🧵overviews the bridge type, span lengths, pier protection, and how the replacement Francis Scott Key Bridge will be constructed. 1/9
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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
@shivon If you reuse the truss steel that fell, it could be functioning in 3 to 6 months. The repair should be put to commercial bid with a massive incentive for early and safe completion.
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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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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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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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@awoooouwuooooo There are several things. Micro cracks develop. Stresses are locked in (meaning some of the total capacity of the rebar is already used up). The method of them yanking it through the machine likely uses some teeth, causing scaring / section loss. Fatigue develops from this.
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The roof of Tropicana Field in St Petersburg has been torn to shreds from Hurricane Milton. This is home field for the Tampa Bay Rays.
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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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@ThinkWiselyMatt Do not do this either. It will fundamentally change the mill certification.
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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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Accurate representation of cable stayed bridge construction sequencing at the miniatures scale.
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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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Hurricane Milton's estimated storm surge for Tampa Bay. A direct landfall to Tampa or landfall to the north will be the worst case scenario for storm surge. The counter clockwise spin of the hurricane will push water into the bay.
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Many such cases when contractors underestimate form pressure from wet concrete. Concrete is 2.5 times denser than water.
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The omnibus spending bill had $8 billion dollars for the Francis Scott Key Bridge replacement. That is way too much money to rebuild the Key Bridge. Easily four times as much as it should cost.
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Hurricane Milton has caused a tower crane to collapse in downtown St Petersburg. The crane landed on the Tampa Bay Times building.
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Rebar and reinforced concrete structures are the backbone of modern society.
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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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What can be improved here? . This catch was gentle!. The shock absorber dampeners were barely engaged when catching a literal rocket falling from the sky.
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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. 6/6
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With Hurricane Milton landfall in Sarasota, which is south of Tampa Bay, the counter clockwise spin of the hurricane literally pulls water out of the bay. Negative storm surge.
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Hurricane Milton's storm surge with landfall near Sarasota. Storm surge flooding does not extend to inland Sarasota due to the elevation above sea level. Port Charlotte and Cape Coral will see significant storm surge since they are south of the storm.
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This is great concrete repair work that will last a long time. Saw cutting for clean edge. Chipping for a minimum pour back thickness. Adding concrete anchors for interface shear transfer. Saturating the old concrete surface before pouring back.
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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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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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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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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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It is not often that the Public Notice contains preliminary information, usually the Coast Guard requires final design prior to issuing the Notice to Mariners. This is a positive sign that permits will be expedited. Thanks for reading my 🧵. 9/9
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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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Folks I am happy to report that my family is all safe and no damage sustained to my home from Hurricane Milton. No power but a cooler morning is fortunate. Natural gas stove means a hot French press coffee this morning.
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This is slip form construction and is commonly used to build barrier walls and drainage gutters. A low slump concrete is used to maintain the concrete shape after it has been formed.
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Thanks for reading my 🧵. I am a Professional Engineer, Bridge Designer, and Design-Build Project Manager. Designing and building bridges over water is my career specialty. I will continue to provide updates on the rebuild of the Francis Scott Key Bridge in Baltimore, MD. 7/7
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