Identification Methods of the Nonlinear Systems Subjected to Seismic Actions

Abstract

The need to identify the nonlinear systems subjected to stochastic actions leaded to the development of the classical and/or deterministic methods toward some methods capable to take into account the improved models for structure and excitation.
The identification of the nonlinear systems can be carried out using specific approaches that are based on the reparability hypotheses or on the change of the nonlinear system with an equivalent linear system that has the features closely related to the initial one.
Current nonlinearities that occur in the structural response during a strong earthquake are geometrical and/or physical (nonlinearity of the stiffness and the damping). In order to underline the nonlinearity of the stiffness, in this paper we take advantage of the modeling method for the structural response using a nonstationary linear model and the parameter identification of the equivalent stationary linear model, both for the SDOF and the NDOF systems.
Explaining the nonlinearity of the stiffness can be done in two specific ways: the structure response modeling through the nonstationary linear model and the parameter identification of the equivalent stationary linear model; the real stiffness valuation of the structure during each vibration cycle using the internal force calculus of the structure.