Constructed in 1953, the Mathews Bridge is one of the major crossings over the St. Johns River in Jacksonville, Florida. It is 7,375 feet in total length, with 59 approach spans consisting of deep plate girders and six channel spans consisting of a cantilevered through truss span structure carrying four lanes of traffic.
In 2007, H&H led a design team for a deck replacement/truss strengthening project that included a structural load rating (LRFR) of the channel through truss structure using 3-D STAAD analysis, detailed design and preparation of contract plans and specifications for the rehabilitation of the through truss channel spans. The rehabilitation consisted of the replacement of the existing open grid steel deck with a new exodermic deck consisting of a five-inch lightweight concrete slab supported by a steel grid deck spanning over new stringers. The new exodermic deck provided a solid deck system that provides additional structural capacity of the existing floorbeams with a composite design, improved corrosion protection of the superstructure and a safer riding surface. Stringer replacement, repairs to the floorbeams, strengthening of truss top chord members, and replacement of the curb and median barriers was accomplished in order to improve the bridge to meet the current AASHTO LRFD Bridge Design Specifications. Post design services were also provided.
In September 2013, the bottom chord of the bridge was struck by a vessel navigating the St. Johns River severing the bottom chord of the main span truss, floor system lateral bracing members, and buckled two floorbeams in the vicinity of the impact. The span might have failed if it were not for the reduncancy of the new exodermic deck that was provided in 2007. H&H’s expertise in truss design and repair was vital in designing the temporary chord, tension jacking system, and deck strong back to maintain the integrity of the truss during the existing chord removal and replacement and reinstate the truss geometry and load back into the bottom chord. The design was completed over a five day period, and construction completed within the 30-day requirement.