Determination of the Forces in X-Frames in Curved Girder Bridges
Start date: 11/01/16
End date: 10/31/19
Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation
About the research
Nationally, concerns remain regarding the design and construction of horizontally curved steel girder bridges due to difficult to predict girder displacements, fit-up issues, and locked-in stresses. One of the more complicated components to analyze and design are the X-frames, due to complexities associated with how loads are transmitted throughout bridges.
In the past, the configuration of X-frames were generally based on standard designs that depended principally on gross geometries and meeting minimum requirements. As such, a unique opportunity exists to improve the design of these components.
A recent study conducted on five curved girder bridges in Iowa revealed that, for modest amounts of curvature, the primary girders can be designed using design principles used for non-curved girders. However, that study focused on bridges with steel diaphragms and primarily focused on the main bridge girders. Furthermore, the prior project focused on the influence of integral abutments, thermal expansion/contraction, and response under live loads. As a result, many questions remain about how X-frames behave, including during various phases of construction.
The reconstruction of the interstate system in western Iowa offers a unique opportunity to monitor the behavior of several yet-to-be-constructed curved girder bridges. The data collected from these bridges will form a strong baseline from which our understanding of whole-life forces can be expanded. These bridges will play a major role in the work.
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