Abstract:In order to analyze the shear lag effect of the multi-cell box girder at the pier with the beam axis as the vertical curve, based on the analogy rod theory, and by substituting the support reaction force equivalent for pier constraint, the axial force and shear force equation of the roof along the bridge axis is obtained to calculate the converted area of each ribbed stiffener and bracing piece at web is calculated. And then based on the compatibility equation of shear deformation, the differential equations set of shear force lag considering ribbed stiffener effect is established. By comparing with the calculation results of the plate and shell finite element model established by ANSYS APDL software, the calculation result of the established equations set shows that the established equation can avoid the difficulty to solve the second-order differential equations which is easy to use, and can reflect the changes in the shear lag effect of the local vertical bending beam. However, the calculation accuracy decreases with the increase of the superimposed and integrated shear flow. As for the bracing piece near the calculated starting end section, the difference value of the stress calculated by the analogy rod method and the stress calculated by the model is about 10.0%. The shear lag coefficient at the maximum stress of the roof of the vertical bending beam is 1.4, which is greater than the shear lag coefficient 1.2 at of the straight beam. The axial stress of the straight beam is reduced by 5.9 MPa compared with the vertical bending beam, which can be considered that the effect of the box beam with vertical bending on the shear lag is unfavorable.
