Miami has long been considered “the gateway to the Americas” due to its location and multi-billion dollar import and export industry. This robust trade industry has led to the establishment of many cargo warehouses located just west of Miami International Airport. Over the years, NW 25th Street (an East/West arterial roadway) emerged as the preferred connection point to the Airport for thousands of cargo/freight trucks entering and exiting Miami International Airport. The existing NW 25th Street facility was an at-grade roadway that traverses two other important modes of transportation within the immediate area – the Northbound/Southbound movement of the Florida East Coast (FEC) railroad and the SR-826 Expressway. This at-grade convergence acts as a source of delay for airport cargo operations.
- The completed grade-separated structure will relieve cargo traffic traveling to and from the Miami International Airport.
- The viaduct serves as an express route to the Palmetto Expressway.
The Florida Department of Transportation developed an overall concept of the new 25th Street viaduct project which encompasses a new 1.4-mile elevated viaduct sky bridge along NW 25 Street beginning west of NW 82 Avenue, traveling over the Palmetto Expressway (SR 826), and ending at Miami International Airport’s Cargo Area. Once complete, the project will improve traffic flow of airport cargo related entering and exiting Miami International Airport by providing an express route for freight/cargo operations. It will also improve local traffic congestion by separating the significant truck volume with an elevated roadway composed of a steel plate girder superstructure on a post-tensioned straddle bent. The viaduct is split into a single-lane, eastbound bridge that is approximately 7,456-feet in length and a westbound bridge that is approximately 7,312-feet in length; together consisting of a total of 41 spans.
The viaduct bridge cross section is composed of a reinforced concrete deck supported on steel plate I-girders with web depths varying from 48, 70, and 96 inches. Spans are typically continuous and range from 100 to 234 feet in length. The east end of the project consists of a four-span horizontally curved superstructure unit on a sharp 460-foot radius.
Based on pier column footprint constraints, the viaduct is supported on steel box straddle bent caps stabilized on reinforced concrete columns or hammerhead reinforced concrete piers. The steel box straddle bent caps range in spans up to 125 feet. They will support not only the mainline viaduct structure, but the eastbound and westbound ramps leading into the Palmetto Expressway. The cap or pier foundations consist of reinforced concrete footings supported on prestressed concrete piles.
The design required extensive use of the MDX and FB-Pier program, STAAD, and other software for analyzing the steel plate girders, steel box straddle bents and pier substructures composed of pier columns and hammerhead piers.