Effect of Secondary Elements on Load Distribution in Prestressed Bridge Girders

Secondary bridge elements, such as barriers, curbs, or diaphragms, are not accounted for when calculating the distribution of load effects to interior and exterior girders, using the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications (AASHTO 2007). This paper shows that including the effect of barriers changes the distribution of loads and, therefore, bending moments in girders. The Florida Department of Transportation (FDOT) Structures Research Lab made field strain measurements on two bridges: a Florida Bulb-T girder bridge and an AASHTO Type IV girder bridge. The Florida Bulb-T bridge strain measurements were taken before and after barriers were placed, and the AASHTO girder bridge was tested only with the barriers. The bridge test results were used to calibrate finite element models, which showed that the barrier, the barrier joint, and the diaphragms affect both interior and exterior girder strains.