Seismic transient change of natural frequency estimation by adaptive filtering scheme

Kirita, Fumio ; Kanazawa, Kenji*; Kitamura, Haruyuki*

This paper presents a new system identification procedure for a time-varying system to estimate natural frequency transition of a building from a strong seismic motion record, named as "Adaptive Forward-Backward Kalman Filter (AFB-KF)". The AFB-KF is compared to the conventional Kalman Filter in the below three points: (1) Forgetting factor for covariance functions to track time-varying structural parameters rapidly, (2) Time-backward estimation scheme and global iteration scheme of the forward and backward processes to estimate unknown initial value of structural parameters, (3) The time series renewal algorithm of statistical properties by reflecting the previous analysis information to improve the identification accuracy. It is useful to accurately identify from natural frequency transition of a building during an earthquake for structural health monitoring which evaluates structural integrity.