A novel adaptive unscented Kalman Filter with forgetting factor for the identification of the time-variant structural parameters

Yanzhe Zhang , Yong Ding , Jianqing Bu , Lina Guo

Abstract

The parameters of civil engineering structures have time-variant characteristics during their service. When extremely large external excitations, such as earthquake excitation to buildings or overweight vehicles to bridges, apply to structures, sudden or gradual damage may be caused. It is crucially necessary to detect the occurrence time and severity of the damage. The unscented Kalman filter (UKF), as one efficient estimator, is usually used to conduct the recursive identification of parameters. However, the conventional UKF algorithm has a weak tracking ability for time-variant structural parameters. To improve the identification ability of time-variant parameters, an adaptive UKF with forgetting factor (AUKF-FF) algorithm, in which the state covariance, innovation covariance and cross covariance are updated simultaneously with the help of the forgetting factor, is proposed. To verify the effectiveness of the method, this paper conducted two case studies as follows: the identification of time-variant parameters of a simply supported bridge when the vehicle passing, and the model updating of a sixstory concrete frame structure with field test during the Yangbi earthquake excitation in Yunnan Province, China. The comparison results of the numerical studies show that the proposed method is superior to the conventional UKF algorithm for the time-variant parameter identification in convergence speed, accuracy and adaptability to the sampling frequency. The field test studies demonstrate that the proposed method can provide suggestions for solving practical problems.

Key Words

adaptive tracking; forgetting factor; model updating; state variable; time-variant parameters

Address

"
(1) Yanzhe Zhang, Jianqing Bu — State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures, Shijiazhuang Tiedao University, Shijiazhuang 050043, China
(2) Yanzhe Zhang — School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, China
(3) Yong Ding — School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China
(4) Yong Ding — Key Lab of Structures Dynamic Behavior and Control (Harbin Institute of Technology), Ministry of Education, Heilongjiang, Harbin 150090, China
(5) Jianqing Bu — School of Traffic and Transportation, Shijiazhuang Tiedao University, Shijiazhuang 050043, China
(6) Jianqing Bu — Key Laboratory of traffic safety and control of Hebei Province, China
(7) Lina Guo — College of Water Conservancy and Civil Engineering, Northeast Agricultural University, Harbin 150048, China."

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