Analysis on warping effect of thin-walled box girders considering coupling between torsion and distortion

To analyze the overall mechanical performance of thin-walled box girders under vertical eccentric loads, and to investigate the amplification coefficients of the warping stresses due to shear lag, restrained torsion, and distortion on vertical bending stress, the governed differential equations comprehensively reflecting vertical bending deformation and warping deformations such as shear lag, restrained torsion, and distortion were established by using the energy variation method on the basis of considering the coupling between torsion and distortion. Theoretical analysis was conducted on the stress statement of the model girder in existing literature and a prestressed concrete simply supported box girder subjected to mid-span eccentric load. The results show that the theoretical values of the stress of the model girder obtained by the governed differential equations are in good agreement with the measured values. The amplification coefficient for the normal stress at the intersection between the mid-span loaded web and the bottom plate reaches about 1.63, and that for the shear stress at the intersection between the horizontal centroid axis and the web reaches about 2.55. Among the warping stresses due to shear lag, restrained torsion, and distortion, the warping stresses due to distortion and restrained torsion dominate, followed by that due to shear lag, but it cannot yet be ignored. © 2023 Southeast University. All rights reserved.