What Bridge Collapse?

Sometimes, I forget that there are people who have not written an entire book about the physics of bridges. So, for those of you who have not been riveted to the news, one of the major bridges in the Baltimore area was hit by a vessel leaving the harbor and collapsed on Tuesday. The bridge is the Francis Scott Key over the Patapsco River. It is part of the I-695 Outer Bridge Crossing - and could carry hazardous materials since it is not one of the tunnels that goes beneath Baltimore Harbor.

The bridge was very beautiful, and built to meet the standards of the time (1970s). As a result, it did not have bumpers or other safeguards around the pilings. And, even if it did have the equivalent at that time, whatever it had would in no way have been capable of withstanding the force of impact with the container vessels of today. I'm in part certain of this because I remember decades ago, being dockside with a RORO barge. The entire thing towered above me in a very disquieting way. The ships we have today make those ships look like bath toys.

So, the debris from the bridge is blocking the channel out of the harbor. The search and recovery of the workmen on the bridge at the time of the collision have been halted because the water is too cold and the debris too plentiful for them to hope to recover the workers at this time. The ship (Dali) did give a Mayday that allowed traffic to be stopped from starting over the bridge before it was hit, but there was not enough time for the workers to exit the bridge.

The city of Baltimore is on the I-95 corridor - one of the busiest in the nation - so anything disrupting traffic there will be felt up and down the Eastern Seaboard. It is also one of the largest ports in the United States - and a major arrival point for cars and farm equipment - which will put a glitch in the supply of new vehicles and equipment. Baltimore is also a harbor for cruise lines that must now determine how to get their passengers on/off their ships. For the cruise industry, working to make up for lost revenue during the pandemic, this is not good news. Other ports are preparing to take up the slack for freight and passengers, but the effects of the loss of a thriving harbor like Baltimore are going to have repercussions for economies outside of Baltimore as well as in Baltimore itself.

Biden has pledged funds to replace the bridge - government funds to foot the entire bill. There are already those asking if that includes demolition and removal of the structure. There is also the problem of the Dali itself, currently sitting with a substantial portion of the collapsed bridge across its bow. Leaking - not sure what - into an area that has a protective floating barrier around it. The Dali also has some number of containers with hazardous materials. All told, the logistics and implications of this collapse are staggering.

Another question relates to the replacement structure. Are pylons adequate for ships the size of those today? Would artificial islands for the pylons be adequate? Would it be best to suspend the entire length of the bridge? Should tugs take cargo ships all the way past the bridge? How long would that take? What about the rest of the bridges that were built to spec decades ago and no longer come close to what we require today?

I'm excited to look at each of these questions. I hope you'll join me.

Video Source: RAW: Francis Scott Key Bridge collapses after being stuck by large ship, wdbj7.com, Mar 26, 2024