box girder;  trapezoidal cross-section;  Twist the heart

Box section is the preferred section type for long-span bridges, and the calculation of the torsional center position of the section is an important part of the internal force analysis of thin-walled box girder structures. According to the Umans second theory of constrained torsion calculation of box-shaped thin-walled girder, the cross-sectional characteristics and torsional center position calculation formula of trapezoidal section thin-walled box girder commonly used in bridge engineering are theoretically derived, and the torsional position calculation formula of trapezoidal section thin-walled box girder with explicit expression is obtained. The numerical example shows that the calculation formula is correct, easy to use, and can be applied to the special case of rectangular section box girder, and the calculation formula has applicability and can be used for practical engineering applications.