Working under a design-build contract with United Contractors, KCI provided design services for seven bridges that had been identified as structurally deficient. The geometry for each bridge was determined with consideration to current FHWA/SCDOT lane and shoulder widths, as well as to site-specific hydrological and environmental requirements.
Bridge spans were maximized through the use of high strength concrete, and durability was added through the use of 5 KSI concrete in the substructure elements and the elimination of bridges joints wherever possible. Due to the low volume of traffic and relatively short detours, new construction at most structures could be completed on existing alignments, minimizing right-of-way and accelerating schedule. Two bridges had to be constructed on a completely new alignment to maintain traffic during construction.
In addition to the design approaches, each site presented a different set of challenges that ranged from utilities to construction methodology. Hollow cored slabs offered a durable option for the superstructures for three low-traffic bridges. A modified drainage system at the abutments at one site protects the backfill material from washing out between the resulting abutment/fill gap that could occur with anticipated long-term settlement of the approach roadway. At one site, the interior bent drilled shaft casings were extended above ground level to bottom of cap in order to eliminate the time needed for forming columns and bent caps separately. Consideration was also given to the needs of the communities within the vicinity of the bridge sites, especially in regards to utility relocation, where continuation of service and cost were factors.