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Flexural Stresses In
Composite Box GirderA
Classical Approach
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INTRODUCTION
A box girder bridge is a bridge in which the main beams comprise
girders in the shape of a hollow box.
The bridges are subjected to different types of loads.
Box girder bridges are commonly used for highway flyovers and for
modern elevated structures of light rail transport.
The bridges are subjected to different types of loads.
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FIGURE 1 : Single celled Composite Box-Girder.
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ADVANTAGES
Structurally efficient because of their high torsional rigidity,
Aesthetically pleasing because of their long span with shallow
depth, and
Highly economical in fabrication and in maintenance because of
their segmental type of construction and their interior space sealed
to provide a noncorrosive atmosphere.
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AIM OF THIS STUDY
To obtain flexural stresses by programming in
FORTRAN using the techniques presented by Y.S. Chenand B.T. Yen.
Comparing the results with that obtained by modeling in
ABAQUS.
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BEHAVIOR OF COMPOSITE
BOX GIRDER
During analysis of a box girder the effect shear lag cannot be neglected
for high ratio of flanges width to span length.
It is necessary to consider the effect and bernouli-naviers hypothesis
is not valid.
Under flexural loading, the flanges sustains in-plane forces along the
line of web to flange junction. Due to this in- plane forces shearing
deformation and non-uniform longitudinal strains, which causes non
uniformity in the distribution of stresses across the width of flanges.This effect is known as SHEAR LAG EFFECT.
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FLEXURAL STRESSES IN SINGLE CELL
COMPOSITE BOX GIRDERS
The development of a procedure for stress analysis of steel- concrete
composite box girders on the basis of classical elastic theory in
following parts of a box girder :
1. Reinforced concrete deck
2. Web of box girder
3. Bottom flange (with longitudinal and transverse stiffners)
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STRESSES IN WEB OF
BOX GIRDER
The normal stress
The shearing stress
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ORTHOTROPIC DECK &
BOTTOM FLANGE
For bottom flange between webs
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For the projecting portion of the bottom flange.
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ORTHOTROPIC DECK &
ISOTROPIC BOTTOM FLANGE
For bottom flanges between webs
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For projecting lips of bottom flange
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ISOTROPIC DECK &
BOTTOM FLANGE
In this case the expression for the stresses in bottom flanges between
webs and stresses for projecting lips of bottom flange are same as in
case of orthotropic deck and isotropic bottom flange.
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