Structural assessment of a prestressed box girder concrete bridge, using non-linear finite element analysis

In this study, it was demonstrated how higher load carrying capacity with respect to shear and torsion can be shown for road bridges through non-linear finite element (FE) analyses. A prestressed box girder bridge, the Källösund Bridge, was evaluated as a case study. The Källösund bridge is a 45 years old, cast-in-situ concrete bridge with four spans, constructed with the free cantilevering method on the west coast of Sweden. The case study indicates a substantially higher load carrying capacity for combined shear and torsion, compared to bridge assessment with conventional design methods. In the non-linear analyses of the Källösund bridge, about 40% higher design bogie load than in the initial structural assessment was reached (B = 250 kN), together with the other design loads in ULS, before a shear failure developed for the studied critical load case. With improvements to the model and with “deformation controlled” loading, an even higher failure load is likely to be shown. However, non-linear analyses of shear failures in this kind of concrete structures are quite rare, and need to be studied further. Furthermore, the analyses performed need to be complemented for other possible critical sections, and for alternative critical load cases