本文研究了弯扭联合作用下梁对突加载荷的塑性动力响应。分析了悬臂折梁和悬臂半园形曲梁自由端受到垂直于梁所在平面的突加载荷时,塑性铰位置和突加载荷大小的关系。由于弯矩和扭矩的交互作用,可能有不同模式的广义塑性铰存在。考察了它们的稳定性并给出了某些数值结果。本文的方法可推广到其他复合应力下梁对突加载荷的塑性动力响应问题。 In this paper, the plastic dynamic response of a beam to sudden load under combined bending and torsion is studied. The relationship between the position of the plastic hinge and the magnitude of the sudden load was analyzed when the free ends of the cantilever folding beam and the cantilever semi-circular bending beam were subjected to a sudden load perpendicular to the plane of the beam. Due to the interaction of bending moment and torque, there may be different modes of generalized plastic hinges. Their stability was examined and some numerical results were given. The method in this paper can be extended to the problem of plastic dynamic response to sudden loads of other composite stress beams.