Damage Detection of Hysteretic Structures with a Pinching Effect: Fid-Bau Portal

Damage Detection of Hysteretic Structures with a Pinching Effect

Yang, Jann N. / Xia, Ye / Loh, Chin-Hsiung

Abstract

Some civil engineering structures, such as RC frames, exhibit hysteretic behavior when subject to dynamic loads, such as earthquakes. The identification of hysteretic systems with stiffness and strength degradations is a practical but challenging problem encountered in the engineering field. A recently developed technique, referred to as the adaptive quadratic sum-square error with unknown inputs (AQSSE-UI), is capable of identifying time-dependent parameters of hysteretic structures. In this paper, the AQSSE-UI technique is applied to the parametric identification of hysteretic RC frames with stiffness and strength degradations and with the pinching effect. The performance of the AQSSE-UI technique will be demonstrated by the experimental data. A $1/3$ -scaled 2-story RC frame has been tested experimentally on the shake table at the National Center for Research on Earthquake Engineering (NCREE), Taiwan. This 2-story RC frame was subject to different levels of ground excitations back to back. The structure is first considered as an equivalent linear model with time-varying stiffness parameters, and the tracking of the degradation of the stiffness parameters is carried out using the AQSSE-UI technique. The same RC frame is then considered as a hysteretic model with plastic hinges following the generalized Bouc-Wen model, and the time-varying nonlinear parameters are identified. The equations of motion of the 2-story RC frame have been formulated based on the finite-element model, and the reduced-order system has been constructed to be used for the damage detection. Experimental results demonstrate that the AQSSE-UI technique is quite effective for the tracking of (1) the stiffness degradation of linear structures, and (2) the hysteretic parameters with stiffness and strength degradations and with the pinching effect.