中文摘要：

基于薄壁箱梁约束扭转理论中有关几何特性的计算过程，导出了双室箱形截面扭转中心及主扇性坐标的实用计算公式，数值算例验证了所推导公式的正确性．结合数值算例，详细分析了双室箱形截面的悬臂板宽度及梁高变化对扭转中心及主扇性坐标的影响．对扭转中心位置的研究结果表明：扭转中心至顶板中面的距离随着梁高的增大而线性增大；当悬臂板宽度小于某一临界宽度时，随着悬臂板宽度的增大，扭转中心位置逐渐降低；当悬臂板宽度超过该临界宽度后，扭转中心位置随着悬臂板宽度的增大而逐渐升高;悬臂板的这一临界宽度随梁高的增大而减小．

英文摘要：

Based on the calculating procedure of the geometrical properties in the restrained torsion theory of thin-walled box girders, the practical formulas for the twist centre and principal sectoral coordinate of a double-cell box section are derived and numerical examples validate the formulas. Combining with numeri- cal examples, the influence of the variations of the cantilever plate width and beam depth on the twist centre and principal sectoral coordinate of the double-cell box section is numerically analyzed in detail. Research on the location of the twist centre shows that the distance from the twist centre to the middle surface of top plate increases linearly with the increase of the beam depth. When the cantilever plate width is smaller than a critical width,the twist centre location lowers with the increase of the cantilever plate width. However, when the cantilever plate width exceeds the critical width,the twist centre location rises with the increase of the cantilever plate width. The critical width of the cantilever plate decreases with the increase of the beam depth.