| The analysis method of thin-walled box girder with variable cross-section warping hasmany kinds, however, mainly by the three-dimensional finite element model to calculate. Inthe model building needs more power and time, in the preparation of input data will alsoencounter the same problem. At the same time, capacity and calculation speed of computershave the very high request. In addition, calculated by the three-dimensional finite elementmodel, the computer gives results (displacements and stresses), both the structure of theoverall response of components and the impact of local stress concentration structure. So theresult is very complex, it is difficult for designers to find out the suitable date to structuraldesign. Therefore, the conventional three-dimensional finite element model application inpractice still have certain restriction.Continuous box for continuous box girder with variable cross section or a diaphragmbeam under eccentric loading, constrained deformation of longitudinal cross section of thefiber, will produce tensile or compression, warping section cannot be freely produces warpingnormal stress and restrained torsion shear stress τ. Based on the thin-walled bar theoryand finite element method. This paper first introduced the basic theory, the definition of thegeneralized displacement function of torsion angle theta θ and warping degree function β.Relationship based on the warping stress and restrained torsion shear stress between τand generalized double torque B and torque T were established through theoretical derivation.Secondly, established the basic differential equation of restrained torsion of thin-walled boxgirder and then defined the application of stiffness coefficient using the initial parametermethod. Finally the variable cross-section box beam constrained torsion element stiffnessmatrix and equivalent nodal loads were derived according to the finite element knowledge.The article also general ideas of reference rod structure finite element analysis, which can beused to analysis beam constraint torsion box discrete one-dimensional calculation program(Fortran program), to find out the warping of arbitrary cross section normal stress andrestrained torsion shear stress τ.As easily accepted method in the engineering design, the one-dimensional finite elementmethod of the linkage compared with conventional finite element shell element and solidelement, has the characteristics of short computing time and less data entry. But the meaningof the computed various physical components is clear, simple, and easily mastered, theadvantage is obvious.Through this study, the following conclusions can be drawn:1. The stress of arbitrary cross-section is obtained by creating variable cross-sectioncontinuous box girder into one-dimensional beam segment unit and being compared to the measured values obtained by the model test. This method has good reliability. Along thespan direction of the beam there is a warping moment, and warping moment at theconcentrated torque acts section and the support section are very large, but it has adistribution characteristic which decayed quickly;2. Model two conditions measured box girder under asymmetric loads to torsion warping,compared with the symmetrical loads under section stress value, the section stress has obviousincreases. The end of the article by comparing the calculated results with the model testresults proves the correctness of the procedure. |
