Barrier Effect on Transverse Load Distribution for Prestressed Concrete Segmental Box Girder Bridges: Fid-Bau Portal

Barrier Effect on Transverse Load Distribution for Prestressed Concrete Segmental Box Girder Bridges

Rambo-Roddenberry, Michelle

AbstractBarriers are purposely omitted from the structural analysis for bridge design or load rating. They are not considered as primary structural members because, after a forceful collision, they may sustain some structural damage and would no longer strengthen the bridge deck. However, when completely intact, these secondary structural members do affect the distribution of applied loads, which is of interest to permitting agencies, such as the Florida Department of Transportation (FDOT). For a prestressed concrete segmental box girder bridge, both design and load rating (for oversized load permits) are determined by longitudinal and transverse analyses without considering the influence of the barriers. For the transverse analysis, the maximum moment generated from the live load is traditionally calculated from Homberg charts. These influence surfaces are based on plate behavior and idealized support conditions and are generally conservative. This moment estimation and the lack of consideration for the barriers create a conservative transverse design and load rating for the bridge. In this study, finite-element bridge models show how much the barrier affects transverse live-load moments on a prestressed concrete segmental box girder bridge. Data obtained from these models were compared with measurements obtained from a FDOT load test and also with predictions made from Homberg influence surfaces, which are often used by engineers in design. The results show that a continuous barrier reduced transverse moments, a jointed barrier behaved more similarly to no barrier, and Homberg design moments were generally conservative. In addition, the joint in the barrier played a large role in transverse live-load effects.