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Flexural Stresses on Bottom Flange of Box Girder.ppt

Apr 14, 2018

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Vishal Mishra
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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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