About the research
With the assistance of the Iowa Department of Transportation (DOT) and three centers at the Institute for Transportation (InTrans) at Iowa State University, Buchanan County, Iowa was awarded a Federal Highway Administration (FHWA) Innovative Bridge Research and Deployment (IBRD) Program grant to help construct and evaluate a replacement bridge that used innovative concepts to increase the bridge’s durability, while also striving to construct the bridge without the use of a traditional overhead crane, making the bridge system an attractive alternative for county workforces and minimizing disruption to the traveling public.
The innovative concepts utilized for this bridge included geosynthetic-reinforced soil (GRS) abutments, high-performance concrete (HPC) with lightweight fine aggregates (LWFAs) for internal curing, and a cast-on-site concrete box-beam superstructure.
Conclusions from the project included the following:
- The use of LWFAs to internally cure the concrete leads to higher strength of concrete and slightly lower weight of the beams.
- Lifting the beams from both ends using two backhoes and moving the beams over the creek was a successful approach and did not cause any damage to the beams beyond some minor bottom flange cracking.
- The load tests performed on the bridge over three years indicated that the bridge joints are well connected and performing well.
- The construction of the beams on-site followed by moving them over the abutments was a time-saving approach, which led to less traffic disruption.
- The GRS abutments did not show any erosion of backfill or any other issues after a flood event occurred in the spring of 2015.
- Results showed that the installation of the vertical sheet drain in one of the abutments provided improved drainage conditions over the abutment without the vertical sheet drain.