The beam displacement is also divided into two parts: one is whole rigid rotating displacement, and another is the combination of rigid-flexible coupling rotating angle and rigid-flexible coupling terms.

• 将梁的柔性振动位移也分解为两部分：由整体刚性回转角所激发的振动(简称动力激励振动)，和由刚柔耦合回转角、梁刚性运动和柔性运动耦合项共同激发的振动(简称刚柔耦合振动)。