الفهرس 
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Abstract
Curved girders are widely used in bridge construction to overcome geographical obstacles.
In such cases, girders with a box cross-section are preferred due to their large flexural and
torsional rigidity. Internal diaphragms are used to limit cross-section distortion and the
distortional warping stress induced in the box girders. However, the use of such diaphragms
hinders girder maintenance. To facilitate the maintenance process, typical cross frames
such as X- or V-shaped truss members are used. Alternatively, access holes are provided
in the solid plate diaphragms.
In this study, the behavior of steel horizontally curved box girders was studied. That
included the distortional warping behavior of the girders and the main parameters that
affect it which proved that central angle of curvature, cross-sectional aspect ratio and
diaphragm spacing had the largest impact on the distortional warping normal stress. A
minimum compliance topology optimization was performed to optimize the amount of
material used in solid diaphragms to more efficient shapes. The effect of the mass retained
percentage and loading case on the optimized diaphragm shapes were examined. A larger
scale of topology optimization was performed on girders that vary in their central angle of
curvature and aspect ratio with the minimum number of diaphragms. The optimized
diaphragm shapes varied significantly with the change in aspect ratio and minimally with
the change in central angles. The corresponding stresses and deformations in the girders
due to replacing solid plate diaphragms with optimized diaphragms were found to be
minimal. Examination of the optimized diaphragms showed a truss like behavior of their
elements.
Refined optimized diaphragms were introduced through refinement and
generalization of the optimized diaphragms. Refined optimized diaphragms and optimized
diaphragms had similar behavior when compared with solid plate diaphragms. A small
increase in the distortional warping angle and vertical deflection and a minor decrease in
the distortional warping normal stress were noticed. The use of refined optimized
diaphragms was tested for change in the diaphragms spacing. Refined optimized
diaphragms were compared with X- and V-shaped cross frames and their impact on the
girders and their load carrying efficiency were recorded. The results showed slight
increases in girder deformations in response to using the optimized diaphragm shapes and
that using either refined optimized diaphragms, X / V diaphragms was more efficient than
using solid plate diaphragms in terms of material used or girder performance