A new point is put forward that transverse bimoment has different influence on the two kinds of cross section thin-walled beams, and on their St-Venant principle conditions. 2.

• 同时对外载等效中经常出现的横向双力矩这一广义力进行研究，指出它在开口和闭口薄壁梁约束扭转问题中和圣维南原理适用条件中分别占有不同的地位。