Analysis of Composite Box Girder in Bridges with Distortion Effects

Abstract

The symbol of bridges is associated with human desires and aspirations to connect, to explore, to achieve ... ali of which ultimately signify the inner rumbling of the eternal search for the meaning of life. On which of the two bridges will Man decide to go, if not on the right one - faith. Beca use faith is a bridge, a bridge between where I am now and where God is leading me and where He wants me to be ... Is this not enough to make the first step through the invisible wall of the unknown? Talking in engineering sense this thought shall light up the desire of achieving more and more. Somewhat merged with the above, bridge constructions in general and especially those with box main girders have always been very popular, first of ali beca use of their suitability, suitability resulting from the high degree of torsional and flexural stiffness. But not being perfect, just as nothing on earth is perfect, the asymmetric loading of box girders causes not only longitudinal bending, but also torsion and distortion, both accompanied by warping. For thin-walled beams, causally related to their "physiognomy", distortion is a significant phenomenon that has an impact on the overall response of the construction. So, asymmetrical loads on box girder bridge decks cause not only bending but also torsion with warping and distortion of the cross-section. The latter two may prove to be relevant for the longitudinal analysis and design of the deck but their effects within the overall structural behaviour are difficult to assess using shell finite element models. However, the researches on the distortional behavior of composite box girders are limited due to its complexity. lnspired by the complexity and knowing that everything we've ever wanted is on the other side of fear, and ali we have to do is cross the bridge, a practical approach to investigating the distortion response of coupled box girders is given. This study is to propose a practical approach to investigate the distortional behavior and get the accurate stress distribution of composite box girders. Considering the differences of stiffness between the top concrete plate and the bottom steel flange, two different distortional angles 0 are assumed at the top and bottom corners of the composite cross section, respectively. Then, the fundamental differential equations of distortion are derived by using energy methods based on the thin-walled beam theory and solved with BEF (Beam on Elastic Foundation) analogy. Both the deformation and the accurate stress distribution of the composite box girder due to distortion are obtained. And to approve the reliability of the analytical approach, a simply supported composite box girder is analyzed and verified by three-dimensional finite-element analyses in software package "ABAQUS". That has been made to shown the simplicity and economical aspect of the analytical approach which provides a distinct insight into the structural response of composite box girders due to distortion. Comparisons were made between the two methods in terms of the theoretical background and the results obtained. ln doing so, a new, practical method is proposed for investigating the distortional behavior of the composite box girders, and for understanding the distribution of stresses in the girders, taking into account the influence of the different stiffness provided by the concrete slab. And as a result of all this inspiration is given for further research on "real" laboratory mini-models to obtain a more reliable criticai comparison of the results obtained through a theoretical, numerical approach and those of the test.