So, I debated posting anything, but as a bridge engineer for over 25 years I'm gonna go ahead and shoot myself in the foot...My post is not intended to start, continue, or finish any arguments.
As I'm sure we all are aware, our highway infrastructure is funded by taxes. Primarily the federal and state taxes on fuels (gasoline and diesel) with some states adding additional user fees to vehicle registration, licensing, and such to contribute. We as citizens generally express a dislike for taxes and wish them to be as low as possible. Politicians write legislation which creates or raises taxes and are very aware that the citizenry is not in favor of taxes. As a result they want to get some positive recognition for the good done by the taxes they impose to help offset the negative press from passing or raising taxes. This means that money available for maintenance and repairs to the highway infrastructure is very limited because this type of work goes largely unnoticed unless it adversely impacts traffic. There is no ribbon cutting, no new shorter or faster way to get from A to B, no new bridge crossing the river - no photo op where the politicians can be seen with your shiny new infrastructure.
So, until the last decade or so very small amounts of money were available to perform needed maintenance and keep our highway system in tip top shape. As a result, the system is in a significant state of disrepair. In the past decade or so this has started to get attention and some additional funding is being allocated now specifically for maintenance activities. It is still not enough to address all the needs, so we occasionally have a major issue resulting in a bridge being posted for lower loads, being closed or even collapsing like the Fern Hollow Bridge in Pittsburg last year. https://www.youtube.com/watch?v=J-VnWB4fiFk
To relate this to the Francis Scott Key Bridge collapse, no owner is going to spend several years worth of their very limited bridge maintenance budget to add additional collision protection to a bridge that has been in service for most of it's design life (50 years for most bridges constructed prior to 2010) without a major incident. Most states have hundreds of bridges that are deteriorated enough to be posted for reduced loads and hundreds more that are on the verge of being load posted if they are not repaired soon. The millions of dollars required to retrofit a collision protection system on the FSK Bridge would allow repairs to and/or replacement of dozens of other bridges that are in poor condition.
I don't work for or with the MDSHA so I don't know any specifics of the condition of the FSK Bridge prior to the collapse, but it is possible that MDSHA was already starting to plan for it's replacement at some future date. Also, federal regulations prohibit the use of federal money to replace a bridge that has had federally funded, non-emergency, repair work for a period of 10 years after the repair work is done. So, if the MDSHA was starting to plan replacement of the FSK Bridge that would be even more reason not to spend money on additional pier protection as it could further delay a replacement contract.
When this bridge was designed (early 1970's) the design requirements for vessel collision were very limited and as noted in earlier posts, the size and more importantly the mass of ocean going vessels was significantly less than the humongous container vessels being built and used today. Also, I'm sure that there were significantly fewer ocean going vessels traversing the world. The world economy was different and many industries that no longer exist in the US were producing goods here that were transported to consumers by rail and truck rather than being imported by ship from other countries.
Vessel collision design requirements for new bridges are significantly better than they were in the 1970's and they are based on the types/sizes of vessels that use the waterway. The resulting costs are included in the costs for the new bridge which if eligible would receive a significant amount of federal funding compared to the limited amount of bridge maintenance funding available to retrofit pier protection to an older bridge.
As Toyman posted, the Ravenel Bridge over the Cooper River in Charleston, SC has huge rock islands around it's main piers. The rocks are as large as a car and were imported by barge from Newfoundland Canada. I couldn't find how many tons or the total cost for these rock islands, but I'm sure it was in the 10's of millions of dollars. Also, the rock islands are much larger than the photo shows as they slope away from the piers below the water line. Again, I could not find what the slope was, but as a minimum it would be at least 2 foot horizontally for every foot vertically (so 10 feet below water the edge of the rock would be a minimum of 20 feet further out than it is at the water line). So the first line of defense is to keep the vessel from contacting the piers and again the design specifications would dictate how far is far enough based on the vessels using the waterway. If the layout did not meet the requirements to prevent contact, then a collsion force would be determined based on the types of vessels and how much energy the protection system could absorb and the piers would be designed to withstand that impact. Also, the Ravenel bridge was designed over 20 years ago and the requirements have continued to change (hopefully for the better) over that time.
TLDR: It is perfectly reasonable that MDSHA hasn't spent a significant amount of their very limited bridge maintenance dollars on upgrading the pier protection system for the FSK Bridge which has served 94% of it's design life without a major ship impact prior to today. Especially considering there are probably hundreds of structurally deficient bridges in MD which need those dollars to prevent them from collapsing due to deteriorated components.
