Abstract: In deducing the differential equation of the box girder contortion (distortion),^[1] we take the shear angle r(z) as the unknown and adopt the plate girder frame method to make the deduction. But the involved process of deriving the formula is comparatively lengthy and tedious. To begin with, we derive them by taking the contortion (distortion) deflection as the unknown, Then we base on the closed thin wall stanchion theory and the energy method, we converse them into the differential equation of r(z). The physical concept is clear and the deduction process is concise. Finally we get the solution of w. By making use of Steinle formula, we deduce the analytical expression of the contorted double moment.

摘要： 箱梁歪扭(畸变)微分方程^[1],以剪切角γ(z)为未知量,采用板梁框架法进行了推导,公式的导演较为繁冗。本文以歪扭(畸变)挠度W为未知量,用闭口薄壁杆件理论与能量法进行推导,然后换算成γ(z)的微分方程。物理概念清楚,推导过程简明,最后求解W,并利用斯坦利(Steinle)公式导出歪扭双力矩解析式。