Nonlinear System Identification of Reinforced Concrete Steel Structure: Using Pseudodynamic Testing Data

Abstract

The research results are presented of the joint project of the National Center for Research on Earthquake Engineering (Taiwan) and Stanford University on the pseudodynamic testing of a three-story full-scale reinforced concrete steel moment frame. Nonlinear stress–strain relations, corresponding to oscillations in the frame, were estimated for successive time intervals from a pseudodynamic test of strong ground motion excitation. Numerical models of the behavior of the frame under the pseudodynamic loading of four levels of input ground motion were constructed and used for estimating changes in the shear moduli in the frame during its loading and for the nonlinear identification of the frame behavior. The contents of linear and nonlinear quadratic and cubic components in the response of the frame were estimated. It was found that the frame possesses mostly odd-order nonlinearities, such as the third, fifth, seventh, etc. order nonlinearities, whereas, even-order nonlinearities, such as, quadratic, the fourth, sixth, eighth, etc. order nonlinearities, are weak. Temporal changes in the behavior of the frame were observed during the test, indicating a substantial decrease in the elastic shear moduli, increase in the absorption of seismic waves and in the contents of the nonlinear part in the response of the frame.