A Precast Substructure Design for Standard Bridge Systems

The proposed substructure system described in this report has been developed to improve the aesthetics and reduce the construction time of the support substructures for standard bridges. The form of the proposed substructures is high attractive, and is a distinct improvement over many traditional short- and medium-span bridge substructures.

The substructure system developed is particularly well-suited for precasting, although the geometric form could be cast-in-situ. Precasting would result in increased use of high performance concrete is greatly resistant to ingress of moisture and chlorides. In addition, the greater compressive strength of the high performance concrete in the substructures. The use of such concrete will bring improved durability since the high performance concrete is utilized for reducing the handling weight and dead load of the substructure units. The bent cap units are more complex than traditional cast-in-place bent caps but appear feasible for plant production or large-scale, cast-on-site projects. The construction method proposed could shorten construction times on-site in certain applications. Shortened construction time, in turn, leads to important safety and economic advantages when traffic disruption or re-routing is necessary

Cost studies based on input from precasters and contractors indicate that if the proposed system (or one quite similar) is actually standardized and used on several projects, the direct costs will be competitive with costs of current designs for concealed bent cap substructures, while the on-site construction time could be reduced substantially. This reduction can have important economic and safety implications on some projects.