BEHAVIOUR AT THE MID-SPAN OF POST TENSIONED, SIMPLE SPAN, SKEWED BOX GIRDER BRIDGES

Author

Shree Krishna Tripathi, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2020

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Hsiao, Jen

Abstract

Many highway bridges are skewed to maintain the profile of natural obstacles to road like rivers, and depressions. Generally, we analyze straight bridge girders making it a line element which makes our hand calculations simpler. However, if we follow the same procedure for skewed bridges like straight ones, we cannot fully visualize and determine their behavior properly which may lead to over estimation or underestimation on different structural forces like bending moment, shear force and most importantly deflection. It is because when we look on skewed bridges in three dimension, the ends of the bridges are skewed to the centerline of the bridges and we can clearly realize that the concrete materials in the acute side is less than that in the obtuse side. If the skew angle is relatively large, it might be the case that there is unbalancing forces along the cross section of the skewed bridge which might lead to the camber at the center of the bridge to be inclined to the vertical which might tend to rotate the entire bridge about the vertical plane. This implies that highly skewed bridges tend to attract more torsion making the design more complicated. If these aspects are not taken into consideration, the skewed bridges might not be good fit while taking the limit state of serviceability. This thesis paper investigates into the three-dimensional analysis of a skewed bridge. Finite element modeling is utilized to analyze the skewed bridges and we can know how it behaves. After the modeling and analysis of a simple span cast in place post tensioned skewed bridge, it is seen that the deflection and bending moment at the mid-span of a skewed bridge is less compared to the non-skewed bridge. Moreover, a skew effect factor is also found which is very useful while designing skewed bridges.