Effects of Skewed Supports on Horizontally Curved Box Girder Bridges
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Date
2024-01
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Addis Ababa University
Abstract
Reinforced concrete overpass bridges are commonly used for modern highway bridges and large urban interchanges. However, in urban areas, space constraints and alignment requirements often make it difficult to use conventional bridge designs. Bridges with in-plan curvature that rest on skewed supports fall into this category, presenting a complex geometrical arrangement. The ERA bridge design manual and AASHTO LRFD design manual have limitations in addressing the combined effects of curvature and support skewness on bridges. They specify an Angle of Curvature below which neglecting plan curvature in determining the preliminary effects of curved bridges is acceptable, as well as shear correction factors for skewed bridges. To assess the structural response of a bridge when these conditions occur concurrently, a three-dimensional Finite Element Analysis was conducted on a multi-cell cast in situ reinforced concrete box girder bridge. Two hundred bridges were modeled with varying parameters. The analysis showed that the bending moment results of skewed bridges are not significantly affected by the incorporation of in-plan curvature. However, there was a significant (15%) difference between the shear response of the approximation method stipulated in design codes and the outputs of this research. To address this issue, a shear correction and magnification factor is proposed for the outermost girders of skew-curved bridges. Additionally, it was found that the girder at the acute corner of the bridge experienced a downward support reaction force, known as an uplift force. This force is magnified when one-lane traffic loading is applied. Furthermore, it was observed that incorporating skewed supports reduces the live load deflection of curved bridges.
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Keywords
Skewed support, Curved Bridges, Reinforced concrete