Institute for Transportation

About the research

The team proposes to design and construct the first bridge in the United States to use a novel concrete mix referred to as ultra high performance concrete (UHPC) in an optimized shape referred to as a Pi girder (i.e., a double tee cross section). Due to the serviceability issues that were identified early on in the conduct of a previous project using UHPC, a modification of the optimized Pi shape will be utilized, but the general cross section shape will be retained. This project will develop and build on experience in Iowa in the design and construction of bridges using advanced materials. To accomplish this, the team proposes to complete the design using only Iowa-based engineers working at various levels (state, local, academia) and, where possible, to use local companies for the construction of the bridge (note: fabrication of the Pi shape girder will likely be done out of state due to specialty formwork issues). The team will also test a reduced-scale beam specimen in the laboratory and test the completed field bridge.

About the research

Using accelerated construction methods, a prestressed, precast bridge, was constructed the by the Iowa Department of Transportation (DOT). The design concept involved the use of precast deck components that were grouted compositely with the steel girders. The successful implementation of this approach has far reaching implications in Iowa as well as nationwide, as there are many instances where proven rapid construction techniques could result in significant reductions in costs.

The overall objective of this project was to assess bridge components and evaluate the overall performance of the 24th Street bridge. In order to complete the objective the project included laboratory test and field testing. The laboratory test included evaluating the shear stud pockets, (including the stud bend test and grout flowability), evaluation of duct splicing performance, and the influence of surface treatment on transverse joint shear transfer. The field test included monitoring strand corrosion, deck panel behavior during placement, post-tensioning strand behavior, and a diagnostic live load test.

About the research

With the assistance of the Iowa DOT and Iowa State Bridge Engineering Center (BEC), Madison County will construct a single span bridge using rapid construction techniques. The BEC will conduct field monitoring on the bridge to help assess the behavior of individual elements during construction, the long-term performance of the individual components, and long-term performance and overall behavior of the completed bridge.