Abstract: Precast U-griders can effectively reduce the height of the line and traffic noise, and can be convenient to maintain. But for U-griders and other open thin-walled members, the beam will occur torsional deformation, which has the effect of bending and twisting except for bending deformation when the loading plane is not a longitudinal symmetry plane, including the centroid principal inertia plane. As the torsional stiffness and shear stiffness of U-griders are much smaller than those of closed thin-walled components or solid section members, it's easy for U-griders to occur torsion instability, resulting in unexpected engineering accidents. Therefore, it is necessary to further study the torsional shear stress and strain of the cross section. In transit of U-griders, there may be only three points of being supported (one point suspended in midair) due to the road irregularity, which will cause torsion deformation of beam concrete. The mechanical properties of U-griders under eccentric loads were studied, and the influence of the torsional shear stress on the structure of U-griders was analyzed, which could provide experimental and theoretical basis for the design of similar bridges.