Modeling & Load Rating of Two Bridges Designed with AASHTO and Florida I-Beam Girders

Florida I-Beam (FIB) girders provide a number of advantages such as higher load carrying capacity, more efficient fabrication, safer construction, increased lateral stiffness, larger vertical clearance and reduction in the overall cost of bridges. A comparative study incorporating two bridges, one with AASHTO Type III and the other with new Florida I-Beam (FIB) girders is presented. The first bridge is a 3 span bridge designed with 6 AASHTO Type III girders. The second bridge has the same length, width and girder depth; however, it has 4 FIB girders. Both bridges are analyzed using the conventional AASHTO LRFD girder line analysis method and also with a more sophisticated finite element method using a commercial software. The details of the FE model are also presented with the critical considerations of link elements, boundary conditions, pre-stressing tendons. Based on the FE model results, it is shown that it is possible to expect 20% higher live load capacity for interior girders and 40% higher live load capacity for exterior girders using FIB-45 girders compared to AASHTO Type III girders, while also reducing the cost by about 24%.