The concept of the equivalent mode and the modal participation coefficient is introduced when the regulation structures are studied . as to the vertical irregular structural systems , the inter - story capacity spectrum method is used and the strength reduction coefficient 77 is put forward when the capacity method is used to evaluate the performance of the torsional irregular structures 对于扭转不规则结构体系,引入与结构偏心矩大小和结构平面整体尺寸有关的强度降低系数叮来考虑结构的扭转效应,选取结构的基底剪力和边轴线的最大反应位移为参数,应用能力谱方法进行抗震性能评估。