Equivalent SDOF systems and nonlinear static (pushover) analysis

This chapter provides the theoretical basis for establishing an equivalent single-degree-of-freedom (ESDOF) approximation of the multi-degree-of-freedom (MDOF) system, and illustrates its use in estimating displacement response using nonlinear static (pushover) analysis. It presents an energy-based formulation of pushover analysis that is particularly useful for representing higher modes, and discusses the difficulties of estimating other response quantities. Nonlinear static analysis, also known as "pushover" analysis, is used to establish the load–displacement response of the system as it undergoes nonlinear response under a prescribed distribution of lateral forces. ESDOF estimates of peak displacement response generally will be close to but not coincide with the displacement response of the MDOF system. The chapter develops an alternative pushover method in which the ESDOF displacement coordinate is computed as an "energy-based" displacement. Nonlinear dynamic response history analyses represent the complicated interaction of multiple modes over time acting on structural components that may respond inelastically.