Evaluation methods of elastoplastic response of components to earthquake motions (Dynamic Analysis of MDOF Systems using elastoplastic response spectrum)

Abstract

For seismic design of components, elastic response spectrum analysis, which is based on linear response using elastic response spectrum, is generally used as a dynamic analysis of multi-degree-of-freedom(MDOF) systems not only elastic response but also elastoplastic response. Elastoplastic response is different from elastic response due to nonlinearity of the system by yielding of components. Several researchers have proposed response spectrum analysis methods of nonlinear MDOF systems using equivalent linearized methods, which replace a nonlinear system to the linear system equivalent to the nonlinear system on the response. We developed a response spectrum analysis method using elastoplastic response spectrum and not replacing a nonlinear system to the linear system as a dynamic analysis method of nonlinear MDOF systems. This method is obtained from exact equations of motions by just two assumptions; no interaction between natural moods and modal combination rules. We verified this method was effective in the calculated 2-DOF systems. This method is also considered of value for interpretation on the response of nonlinear MDOF systems by spectrum modal approaches.