| At present, most of bridges that have been built or are under construction are pre-stressed concrete continuous girder bridges, particularly pre-stressed concrete continuous box girder bridges. However, along with the construction of such kind of bridges, more and more bridge cracking during construction or operation is reported. This paper is committed to analyze the reason for box girder cracking through studying the finite element calculation method of constraint torsion and distortion effect of box girder under unbalanced loading, expecting to provide with reference of eccentric-loaded coefficient for designers.During the process of finite element deduction of constraint torsion of box girder, taking the torsion angle as unknown and the general solution of constraint torsion differential equation of constant section as interpolation function, based on Umanski Second Theory, and through virtual work principle, element stiffness matrix and load arrays of constraint torsion have been deduced. And during the process of finite element deduction of distortion effect of box girder, taking the distortion angle as unknown and the general solution of distortion differential equation of constant section as interpolation function, based on plate girder framework, and through virtual work principle, element stiffness matrix and load arrays of distortion effect have been deduced. During the calculation, interactions between torsion and distortion are ignored.Through adopting Fortran to program and comparison between the calculation result and analytical examples, the paper finds out the finite element method is not only practical but also has high accuracy. In this paper, an1:4experimental model is made in the background of Guangzhou Quansheng Bridge, the torsion and distortion stresses are calculated separately under different loading condition through the program, and the results are compared with the real results. Moreover, eccentric-loaded coefficients of the model bridge under different conditions are calculated to provide with an envelope diagram of the eccentric-loaded coefficient, pointing out the deficiency of empirical coefficient method to determine the eccentric-loaded coefficient. |
