Parameter identification for degrading and pinched hysteretic structural concrete systems

Hysteretic models are frequently used to predict the non-linear behavior of reinforced concrete structural systems. Such models are typically characterized by control parameters that have to be calibrated from observed experimental testing. A system identification methodology is presented in this paper for determining the values of control parameters in a continuously smooth hysteretic model for inelastic dynamic behavior of structural concrete systems. The technique is based on a modified Gauss-Newton approach in which a non-linear relationship between model parameters and the force-deformation or moment-curvature hysteretic loops is assumed. The methodology is applied to an extended version of the well known rate-dependent Bouc-Wen hysteretic model. Six control parameters are introduced into the model which influence the degrading characteristics and, therefore, represent the target parameters that need to be optimized. The versatility of the approach is demonstrated through sample simulations of observed behavior which are drawn from reinforced and partially prestressed concrete elements and subassemblages including beams, columns and beam-column joints. Studies of convergence of the proposed algorithm and sensitivity of the model to identified parameters is presented.