The main principles of seismic-resistant design of buildings and structures allow the propagation of significant plastic deformations under large earthquakes. But the possibility of total collapse should be ruled out. To fulfill these conditions it can be done the comprehensive dynamic plastoelastic analysis using modern software. But full dynamic plastoelastic analysis is very labor-consuming and inconvenient for design decisions.

In the present research a nonlinear dynamic analysis of the multi degree of freedom system together with nonlinear single degree of freedom system are used for analyzing the behavior of structures under plastoelastic deformation. The validity of the application of a nonlinear single degree of freedom system is analyzed by comparing the results obtained by single degree of freedom system with the results from nonlinear dynamic analysis of the multi degree of freedom system.

In the paper recommendations for application the nonlinear single degree of freedom system are proposed.