Access Type

Open Access Dissertation

Date of Award

1-1-2010

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Civil and Environmental Engineering

First Advisor

Gongkang Fu

Abstract

In the US, nearly 33.5% of highway bridges are skewed. In the past, these skewed bridges have been analyzed as straight bridges. Nevertheless, there exists an extensive literature indicating the mechanical behavior of skewed bridges being quite different from their straight counterparts. In this thesis, to better understand the behavior of skewed bridges, experimental, numerical, and analytical researches have been conducted. The analytical method proposed here is the first of its kind in the skewed bridge research, and is expected to aid the bridge engineers with their design.

First, a three dimensional finite element analysis (FEA) model was developed and was calibrated by the physical measurement results of a real skewed bridge over M-85 and I-75 in Michigan. In this FEA model, generic bridges with various parameters such as different diaphragm types, bearing types, girder spacings, girder types, span lengths, and skew angles were analyzed to study the behavior of skewed bridges. The results were compared to the AASHTO-LRFD Specifications and as expected it was observed that the specifications does not cover all the aspects of a skewed bridge behavior.

In addition, analytical solutions for skewed thick plates under transverse load and skewed bridges subjected to truck load were developed. The thick plate solution was obtained in a framework of oblique coordinate system. The governing equation in that system was first derived and the solution was obtained using the deflection and rotation as derivatives of a potential function developed here. The solution technique was applied to two illustrative application examples and the results were compared with numerical solutions. The two approaches yielded results in good agreement. Then, skewed beam bridges were modeled as an assemblage of several individual skewed thick plates supported on beams. To confirm the validity of the analysis process and the solution obtained, the moment and shear responses to truck loads are acquired using the analytical method and compared with that from FEA. In addition, the lateral distribution factors for moment and shear used in routine design is investigated based on comparison of the analytical approach and FEA.

Finally, suggestions for future research are presented, including development of the temperature effect analysis and dynamic analysis. These analyses will provide further understanding of the behavior of skewed bridges.

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