Feature extraction and system identification of reinforced concrete structures considering degrading hysteresis

From the point of view of structural safety monitoring, the state of damage after severe loading becomes an important issue for safety evaluation. In this study, seismic response data of a total of four reinforced concrete frames, designed with same dimensions and same seismic design code, subject to different levels of ground excitation individually from shaking table test, are used to study the nonlinear and damage pattern of reinforced concrete structure. First, the signal-based damage identification method, which include the change of the Hilbert marginal spectrum, the instantaneous frequency and phase difference, the Holder exponent, and the wavelet component energy distribution, is applied to identify the nonlinear features of the structure. Then the general Bouc-Wen hysteretic model was used to identify the physical parameters such as stiffness degradation, strength deterioration and hysteresis behavior of the reinforced concrete frame. Finally, the relationship between the change of model properties, the global damage index and the identified damage features are investigated. The relationship between the identified stiffness degradation function and the identified structural nonlinear/damage features can be used as a safety assessment index for the seismic assessment of reinforced concrete structure. Copyright (C) 2010 John Wiley & Sons, Ltd.