The replacement of the Francis Scott Key Bridge is a critical need for the City and Port of Baltimore--indeed, for this entire nation. Fortunately, the steel industry has the experience, expertise, material, and ability to quickly get the job done.
President Biden boldly called for it to be replaced with American steel--and our nation’s steel industry is ready and able to answer the call. Our steel mills are already producing the plates and shapes that will be needed. Our steel fabricators and erectors are skilled and capable to make the parts and put them in place. Quickly. They’ve done it before and have systems that work.
Many bridge design experts believe a cable-stayed bridge will allow the fastest and most serviceable solution. A number of recent projects show how useful and practical this style of steel solution is: the Governor Mario M. Cuomo Bridge, the Gordie Howe International Bridge, the Lewis and Clark Bridge in Kentucky, the Stan Musial Veterans Memorial Bridge, the John James Audubon Bridge in Louisiana, and the Kosciuszko Bridge in NYC, to name a few examples.
With that in mind, we asked one of the industry’s leading experts, Ronnie Medlock, Chair of the Technical Committee of the National Steel Bridge Alliance (NSBA) and Vice President of High Steel Structures in Lancaster, Pa., about the ways that this vital project can be completed quickly and economically with steel.
He confirmed that the cable-stayed steel solution is a great one for an accelerated project schedule. The steel is fabricated while the towers are being constructed and ready to be erected when the supports are ready. That also allows the whole team the opportunity to collaborate and decide the best approach for all of the key steel fabrication and erection details.
A hallmark of accelerated bridge construction is cooperation among the fabricator, contractor, and engineer. They work closely together as details are developed and shop drawings are prepared and approved. In cable-stayed bridges, one or two key details multiplied, for example, over dozens of cable anchor assemblies or connections to edge girders can significantly streamline the whole project.
To ensure the fastest and least expensive project, Medlock made some important recommendations:
- Connection details between the floor beams and edge girders should be configured to allow fabrication without the need for shop assembly of the floor system. As an example, on the Lewis and Clark Bridge (Louisville East End crossing), High Steel Structures only did one check assembly for the entire floor system, with two edge girders and three floor beams assembled as a proof of this concept. That was all that was necessary for these connections--the right details save an extraordinary amount of time and money.
- Cable anchor details are commonly called "rocket launchers" today. The details used for them can have an impact as powerful as a rocket on the speed and cost. One key decision is whether to go with a bolt-on rocket launcher or an integrated shark-fin style rocket launcher. High Steel has done both, and both work, but the bolt-on style is much faster. With a well-detailed, bolt-on rocket launcher, rocket launcher fabrication can proceed in parallel with girder fabrication, boosting speed. Furthermore, there are details in the rocket launcher that can significantly improve time and geometry control. In particular, the arrangement of plates and use of fillet welds instead of groove welds also facilitate speed and cost savings.
- For the coating system, this application and the need for a fast schedule will likely lead to a choice between two options: a three-coat system (an organic zinc primer, an epoxy intermediate coat, and a urethane topcoat) or a two-coat inorganic system (an inorganic zinc primer with an inorganic topcoat). Medlock recommended the latter, because it offers similarly robust protection but would likely be faster with improved curing time, no need for masking, and only simple touch ups required in the field. The coating decision is independent of the bridge design and can be made a bit later--but not too much.
The faster these decisions are made, the sooner the bridge can be reopened. The entire American steel construction industry is committed to the success of this project and is ready, willing, and able to assist with this challenge. Together, we can get traffic and vital commerce moving again.