The growing need to upgrade Canada’s aging highway bridge network requires the development of innovative solutions that will lead to the construction of long life bridges with low life cycle costs. Ultra high performance concrete (UHPC) is a newly developed concrete material that provides very high strength and very low permeability, which could enable to provide major improvements over conventional high performance concrete (HPC) bridges in terms of structural efficiency, durability and cost-effectiveness. In this paper, the optimum use of UHPC is determined for the case of cast- in-place HPC slab on UHPC precast/prestressed girder bridges. These bridges are designed according to the serviceability and ultimate limit state requirements of the Canadian Highway Bridge Design Code with additional special requirements from existing recommendations for UHPC design. An iterative design procedure with preliminary design stage and refined stage using finite element method will be used in this study. This paper shows that the use of UHPC in precast/prestressed concrete girders enables a significant increase in the bridge span of the slab-on-girders bridge when compared to conventional HPC bridge girders. UHPC yields a considerable reduction in the number of girders and girder size when compared to HPC bridge of the same span length, and hence results in a significant cut of concrete volume from 49 % to 65 %. On the other hand, the study shows that the reduction of the girder spacing yields a high increase of the span length of the UHPC-bridge, while less improvement is observed for the HPC bridge. Four UHPC girders represent the best choice for the minimum CPCI girder size, which are able to support the maximum feasible precast girder length.
Menu
