NW 25th Street Viaduct

Miami is considered “the gateway to the Americas” due to its location and robust dollar import and export industry. The trade industry has led to the development of numerous cargo warehouses just west of Miami International Airport (MIA). Over the years, NW 25th Street, an east-west arterial roadway, emerged as the preferred connection point to MIA for cargo and freight trucks.  

The existing NW 25th Street facility was an at-grade roadway traversing two other vital 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 created a traffic bottleneck and delays for airport cargo operations. 

The Florida Department of Transportation developed an overall concept for the new 25th Street viaduct, which comprised a 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 MIA’s Cargo Area. TYLin provided comprehensive bridge design and structural engineering services to prepare the concept for construction.  

The viaduct cross section consists 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 cap or pier foundations consist of reinforced concrete footings supported on prestressed concrete piles. 

Project Highlights: 

• The project improves the flow of airport cargo traffic by providing an express route for freight and cargo operations. 
• Local traffic congestion is mitigated by separating the heavy truck volume with an elevated roadway composed of a steel plate girder superstructure on a post-tensioned straddle bent. 
• Consisting of 41 spans, the new viaduct is split into a single-lane, eastbound bridge close to 7,456 feet long and a westbound bridge about 7,312 feet long. 
• The steel box straddle bent caps range in spans up to 125 feet and support the mainline viaduct structure and the eastbound and westbound ramps leading into the Palmetto Expressway.
• TYLin’s 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.