Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation
Behrouz Shafeishafei@iastate.edu email >
Structural Engineer, BEC
Brent Pharesbphares@iastate.edu email >
Bridge Research Engineer, BEC
About the research
While for decades horizontally curved steel girder bridges have been a solution for constructing interchanges between state and Interstate highways, concerns remain regarding their design and construction. The cross-frames in these bridges are especially critical because, unlike in straight bridges, they are major load carrying elements.
The design and analysis of cross-frames in curved bridges is complex due to complexities in how loads are transmitted throughout these types of bridges. However, a unique opportunity exists to improve the design of these components using modern computer software and short- and long-term monitoring.
This project investigated a horizontally curved bridge located in Story County near Ames, Iowa, to understand the behavior of cross-frames during construction and over the service life of the bridge. The project involved a numerical investigation using finite element modeling and short-term and long-term monitoring in the field to (1) identify sections of the bridge to instrument under dead, live, and temperature loading; (2) evaluate the performance of cross-frames through long-term monitoring; (3) evaluate the performance of cross-frames using live load tests; and (4) provide recommendations for practice.
The research results suggest that the cross-frames close to supports may experience high stress levels, and therefore special attention is required for their design compared to the other cross-frames. The cross-frames within the interior bays were also found to carry higher forces than those in the outer bays. This situation requires additional analysis during design to ensure the safety and performance of curved girder bridges.