The response spectrum method is useful for illustrating overall characteristics of dynamic behavior as well as for estimating seismic response of structures. We proposed an estimation method for nonlinear response based on the effective period of transient vibration. The formula of the effective period is derived from backbone curve which has been discussed in the area of nonlinear vibration theory. Parametric response analysis of elasto-plastic and origin-oriented single-degree-of-freedom systems subjected to pulse-wise sinusoidal excitation was carried out. The results of response analysis were compared with the values estimated by the proposed method, and accuracy of the estimation method was examined.
