I was listening to the radio yesterday, and noticed that others had your question about the quick collapse of the bridge upon impact. Here's the transcript of the piece I heard, in which the host described the bridge going down "as if it was made of toothpicks." I can imaging a class using some of this audio and transcript in a multi-media primary source lesson about bridge design, and the role of fenders or barrier rings to protect bridges. A follow up piece, also explained very simply, with a bridge engineering expert, is here. 

Also, in a STEM-focused class, the physical forces of propulsion, momentum, and direction that affected the ship that struck the bridge are a rich topic to explore in this awful event. This other brief radio piece, again with transcript, raises the causal factors of

• ship design (one propeller, more than one engine and fuel source, but back-up systems dependent on electricity),
• tides and the moon and their effect on river current, and
• the actions of the ship's crew in dropping an anchor to attempt to stop the ship before impact, and how quickly a dropped anchor can stop a boat.

So timely and just a great set of resources and points of entry to investigate. I think it could also be interesting to look and see if there are images of ships going under that bridge when it was newly constructed vs. the size/weight of the ship that struck it yesterday. It begs questions about infrastructure upgrades for changing conditions, uses and needs. What else might be in need of new ways of thinking? Also I was caught thinking... have there been a lessening of regulatory requirements over the years that led to this situation happening? Tons of lanes to inquire and investigate. Thanks for the legwork on this! So helpful.

Wired actually delves into the physics of a truss bridge.  They are popular designs in the balsa bridge building competitions, but for modern multi-modal transportation and shipping they are not always the best option. 

 Large steel structures may seem invulnerable, but steel, explains Knight, is relatively lightweight for its size. As soon as it is pushed or pulled the wrong way with enough force, it can fold like paper. In this case, the Francis Scott Key Bridge was a “continuous,” or unjointed, bridge that had a 366-meter-long central truss section. (Truss bridges use steel beams, arranged in triangular shapes, to support their load.) The central truss was made up of three horizontal stretches, known as spans, with two sets of supports holding these above the water. It was the third-largest structure of its kind in the world.

“When you take a support away, there is very little in the way of robustness,” says Knight. “It will drag down, as we saw, all three spans.” The separate approach spans remain standing.

Bridges in Baltimore, Maryland State Archives

Framework for Improving Resilience of Bridge Design, Federal Highway Administration, LOC Collection