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) The bridge has three different superstructure types.

The channel span is a moveable structure called a bascule, aka a draw bridge.

Steel plate girders extend for several spans, but the barge struck the third type.

Furthest from the channel, a concrete beam span fell. (2/10)

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) 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)

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?

1/8 This would be a monumental ask of the Baltimore Gas and Electric company.

Especially because these were only just recently relocated to overhead.

A new temporary directional bore can be done and should take a few months, if accelerated.

This provides a better work zone. 2/8

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

https://twitter.com/elonmusk/status/1773931137531810233

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

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 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