PREDICTION OF GLOBAL AND LOCALIZED DAMAGE AND FUTURE RELIABILITY FOR RC STRUCTURES SUBJECT TO EARTHQUAKES

This paper deals with the prediction of global and localized damage an d the future reliability estimation of partly damaged reinforced concr ete structures under seismic excitation. Initially, a global maximum s oftening damage indicator is considered based on the variation of the eigenfrequency of the first mode due to the stiffness and strength det erioration of the structure. The hysteretic behaviour of the first mod e is modeled by a Clough and Johnston hysteretic oscillator(1) with de grading elastic restoring force. The linear parameters of the model ar e assumed to be known, measured before the arrival of the first earthq uake by non-destructive vibration tests or by means of structural anal ysis. The previous excitation and displacement response time series ar e employed for the identification of the instantaneous softening using an ARMA model. The hysteresis parameters are updated after each earth quake. The proposed model is next generalized for a MDOF system. Using the calibrated model for the structure and the global damage state, t he global damage in a future earthquake can then be estimated when a s uitable earthquake simulation model is applied. The performance of the SDOF hysteretic model is illustrated on RC frames which were tested b y Sozen and his associates.(2,3) (C) 1997 by John Wiley & Sons, Ltd.