Parameter identification of degrading and pinched hysteretic systems using a modified Bouc–Wen model

The Bouc–Wen (BW) model is a successful differential equations model used to describe a wide range of
nonlinear hysteretic systems. However, it is unable to describe force degradation, stiffness degradation
and pinching effects. Therefore, Baber and Noori proposed a generalisation, developing the Bouc–Wen–
Baber–Noori (BWBN) model. Nevertheless, it is composed of many parameters and complex pinching
and degrading functions. Thus, it is necessary to develop a simpler and reliable model to be used for
practical applications. In this paper, a modified BW model is proposed. It involves a more direct physical
meaning of each parameter and allows achieving a substantial reduction of computational effort and
numerical deficiencies. This is obtained through simpler pinching and degrading functions that entail a
decrease of the number of parameters. The result is a straightforward model, capable of predicting the
behaviour of degrading and pinched hysteretic systems. An application of the proposed scheme to a
real case is also presented, in which reinforced concrete bridge piers that were physically tested in the
laboratory are considered. The force–displacement data are used to perform the identification process of
the model parameters via a Genetic Algorithm. The numerical results are accurate since they coincide with
the experimental ones.