Simplified Analysis Method for Deflection of Thin-Walled Box Girder

In order to find a simplified method for calculating the deflection of the thin-walled box girder under the influence of shear deformation, the flexural deformation of the thin-walled box girder is analyzed on the basis of the unit force method. Firstly, by analyzing the distribution mode of the flexural shear stress of the thin-walled box girder, the expressions for the shear influence coefficients of each wallboard constituting the box girder are derived. With the shear influence coefficient, the analytical expression of the simple box girder deflection can be deduced by using Timoshenko beam theory. Secondly, the beam segment analysis model of the box girder is built by using the Castingliano’s second theorem and the program is compiled for solving the complex structure such as the box girder with variable sections. Finally, the example models of the box girders with constant and variable sections are analyzed. The results of numerical examples show that the error between the deflection calculated by the program and the measured and the ANSYS finite element results is within 3%. For the numerical example, the deflection of the box girder is increased by more than 20% due to the shear deformation. Parametric analysis also indicate that the additional deflection caused by the shearing of the flange increases with the width-to-height ratio, whereas for the web, the case is the opposite.