Damage Identification of Frame Structures with Joint Damage under Earthquake Excitation

Abstract

Previous damage detection of frame structures mainly focuses on the detection of beam and column element damage. It has been shown that beam-column joints in frame structures are more susceptible to damage than the other members in the structure. Joint damage may be represented by the reduction of beam-column connection rigidity. Therefore, damage detection of a frame structure with joint damage includes the identification of joint connection stiffness in additional to those of beam and column stiffness, which involves the difficulty of identifying a large number of unknown structural parameters. In this paper, an algorithm based on a two-step Kalman filter approach is presented for the damage detection of frame structures with joint damage under earthquake excitation using partial measurements of structural acceleration responses. Recursive solutions for unknown structural parameters and structural state vector are derived by a two-step Kalman filter, respectively. Therefore, the number of unknown variables to be estimated in each step is reduced compared with the conventional Extended Kalman filter (EKF) approach. Structural damage is detected from the degradation of the identified stiffness values of joints, beam and column elements of frame structures. A numerical example and a lab experiment test data are used to validate the performances of the proposed algorithm for damage identification of various joint damage scenarios in frame structures under earthquake excitation.