Abstract: The multi-degree-of-freedom system is equivalent to the single-degree-of-freedom system according to the characteristics of RC frame structures.The equivalent parameters of the single-degree-of-freedom system are calculated.A newly-modified method of displacement-based seismic design is presented.The seismic performance is divided into five levels,i.e.function integrity,function continum,damage control,loss control and life-safety,and different levels are quantified with storey drift ratios.Comp...