By applying a set of virtual concentrated loads to the structure and performing a static solution once only, the desired influenceline can be obtained.
按照这种方法，只须在结构上施加一组虚拟荷载，进行一次静力求解即可得到指定截面的内力影响线。
2
The problems involve the correct expression of the rule of three rigidity pieces, the proving of the proposition about symmetry and possibility of reducing contents about the influenceline etc.