关键词: 变截面, 连续箱梁, 约束扭转, 应力放大系数

Abstract: In order to study the characteristics of stress distribution and deformation of box girder bridge with variable cross section, the element stiffness matrix of box girder with variable cross section is derived based on the restrained torsion differential equation of box girder.Based on the analysis of the project, three load distribution conditions are set up, and the bending moment and warping displacement of box girder with variable cross-section are calculated, the stress amplification effect is also studied.The results show that the curves of moment changing with longitudinal distance in case 1 and case 2 are similar and show “W” shape.In condition 3, the trend of change was just opposite, myopia presented “M” type, and both the value and the range of change were small.The warping displacements are mainly concentrated at the end and the middle of the side span, and show an anti-symmetric distribution with the mid-span section as the boundary.In case 1 and case 2, the values of the generalized warpage displacement in mid-span and right-span are basically the same.The curve of warping double moment shows the law of attenuation from the peak point to the two sides, and the extreme value appears at the position of the center fulcrum and the action point of the concentrated load.The maximum normal stress of warpage occurs in the section under the action of concentrated load. The stress magnification coefficients of the four control sections are less than 1.41 under three loading conditions.

Key words: variable cross section, continuous box girder, constraint Twist, stress amplification factor