Systems Identification of Degrading Hysteretic Restoring Forces

A degrading, hysteretic restoring force model for structures subjected to extreme dynamic loads has been developed by Wen (1976; 1980) and Baber and Wen (1981). A need has arisen for systematically identifying the parameters of this model. A brief discussion of the model is first presented here along with an extension developed to model displacement‐dependent degrading behavior of reinforced concrete structures. A method for identifying the parameters of the model, given observed structural response, is then developed. The method is based on a classic, time domain‐least squares procedure where the system parameters are obtained by solving a system of simultaneous linear equations. The parameter identification method should prove useful in developing models of complex structures for nonlinear, random vibration analysis. Based on applications of the parameter identification method, using actual structural restoring force experimental results, simple rules for determining the model parameters are suggested and presented at the conclusion.