Determination of the Forces in X-Frames in Curved Girder Bridges

Project Details
STATUS

Completed

PROJECT NUMBER

16-594, 17-SPR0-019

START DATE

11/01/16

END DATE

04/30/21

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation

Researchers
Principal Investigator
Behrouz Shafei

Structural Engineer, BEC

Co-Principal Investigator
Brent Phares

Bridge Research Engineer

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.

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